Patent Description:
The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

Masonry heaters are devices used to heat the interior of a building by absorbing the intense heat of a fire into masonry material and gradually releasing the heat over a period of hours. Although the radiant heat released by the masonry heater is low compared to other heaters, the temperatures inside masonry heaters can reach in excess of <NUM> °F (<NUM>) - far more than conventional metal furnaces can handle. Efficiently and effectively capturing and transferring the intense heat from masonry heaters to other devices would drastically reduce the energy required to heat other areas and/or fluids. However, previous attempts to capture and transfer heat from masonry heaters have been less successful than desired.

<CIT> relates to a water boiler which is adapted for use in a fireplace, having an inlet header pipe, an outlet header pipe, and a series of pipes disposed parallel to one another and connected between the inlet and the outlet header pipes. The series of pipes is fashioned so as to form a grate suitable for supporting a log fire, including a horizontal portion upon which the logs may be supported and a remaining portion which extends upward along the rear wall of the fireplace through an arc back toward the top front of the fireplace, whereby heat rising from the fire passes between the series of pipes for added boiler efficiency. A heating system using the fireplace boiler and operating in conjunction with a conventional residential heating system is also disclosed. The fireplace boiler contributes heat a conventional furnace to reduce the amount of energy consumed by the latter.

It is the object of the present invention to provide an improved heat transfer apparatus for a masonry heater.

The object is solved by the subject matter of the independent claim.

Exemplary embodiments are illustrated in the referenced figures. The embodiments and figures disclosed herein are intended to be illustrative rather than restrictive.

One skilled in the art will recognize many methods, systems, and materials similar or equivalent to those described herein. The present invention is in no way limited to the methods, systems, and materials described.

Embodiments of the present invention relate to apparatuses and systems for capturing and transferring heat from a masonry heater to a device external to the masonry heater. It is desirable to capture the heat from a masonry heater to increase the overall efficiency of a household and reduce the cost of heating water and air, for example, during cold winter months. Embodiments of the present invention significantly improve the amount of energy captured and transferred from a masonry heater compared to previously known designs.

Referring to <FIG>, masonry heater <NUM> is composed primarily of a masonry material, such as stone, brick or tile, instead of metal. Fuel, usually wood, is burned in the firebox <NUM> of the masonry heater <NUM> where temperatures may exceed <NUM> °F (<NUM>), causing combustion of nearly all gases in the firebox <NUM>. In contrast, metal stoves are designed to vent gases to prevent the gases from melting or damaging the metal housing. Once the fuel is lit in the firebox <NUM>, the masonry absorbs and slowly radiates the heat outward over a period of several hours at a relatively constant rate. A secondary burn chamber <NUM> ("oven") is typically located above the firebox <NUM> and fitted with a door for cooking, although the secondary burn chamber <NUM> is not necessary for a fully functional masonry heater <NUM>. Masonry heater <NUM> may have varying shapes, including cylindrical, square, rectangular or tapered designs. Masonry heater <NUM> may also have smoke channels located between the firebox <NUM> and the chimney to further absorb and evenly distribute heat. As those of ordinary skill in the art will recognize, masonry heater <NUM> may come in varying shapes and sizes, and have additional design features not illustrated in <FIG> without departing from the description and illustrations contained herein.

<FIG> illustrate an embodiment of a heat transfer apparatus where lengths of coil pipes <NUM> are disposed in the firebox <NUM> of a masonry heater <NUM>. In this embodiment, the coil pipes <NUM> are oriented in a substantially horizontal manner near or at the top of the firebox <NUM>. As shown in <FIG>, the coil pipes <NUM> extend across a substantial portion of the firebox <NUM> to increase the area of coil pipes <NUM> that are directly exposed to heat. The coil pipe <NUM> may be located farther down in the firebox <NUM> to the heat source; however, this may decrease the space available for placement of fuel and may not significantly increase performance of the heat transfer apparatus. <FIG> illustrates a side view of the horizontal orientation of the coil pipe, where the coil pipes <NUM> extend into the firebox <NUM>, and a temperature sensor is located within the firebox <NUM> in a liquid return path of the coil pipes, as discussed later in more detail. Alternatively, the coil pipes <NUM> may extend from a side wall or other wall of the masonry heater <NUM>, as long as heat from the firebox <NUM> intersects with the coil pipe <NUM> in a direction substantially orthogonal to the direction in which the coil pipes <NUM> extend. In <FIG>, two coil pipes <NUM> are illustrated at the top of the firebox <NUM> to maximize the amount of heat and power captured and transferred from the firebox <NUM>, however, a single coil pipe <NUM> or more than two coil pipes <NUM> may be installed in the firebox <NUM> without departing from the scope of the heat transfer apparatus or heat transfer system described herein.

<FIG> illustrate an embodiment of a heat transfer apparatus where coil pipes <NUM> are oriented in a vertical manner in the firebox <NUM>. Typically, the coil pipes <NUM> are installed adjacent to the sides of the firebox <NUM> in this configuration to allow access to the coil pipes <NUM> for maintenance, and to maximize the available space for stacking wood or other fuel. In this configuration, liquid enters the firebox <NUM> at the bottom end of the coil pipe <NUM> and exits the firebox <NUM> at the top end of the coil pipe, which promotes evacuation of any accumulation of gases in the heat transfer apparatus, as described later. As illustrated in <FIG>, a first temperature sensor <NUM> is located within the firebox <NUM> in a liquid return path of the coil pipe <NUM> at the top end of the coil pipe. The first temperature sensor <NUM> extends through wall <NUM> and far enough into the firebox <NUM> to obtain an accurate measurement of the liquid at its hottest point, before the liquid exits the firebox <NUM> and begins to cool. A vertical orientation may be preferable to the substantially horizontal orientation where access to the interior of a masonry heater <NUM> is limited, or where such an orientation is preferable due to the type or style of masonry heater <NUM>, such as a double bell masonry heater <NUM>. It is important to orient the coils to permit access to the coil pipes <NUM> for maintenance and repair purposes. Although two coil pipes <NUM> are illustrated in <FIG>, any number of coil pipes <NUM> may be oriented in a vertical manner within the firebox <NUM> to achieve the desired amount of heat transfer.

The coil pipe <NUM> orientations shown in <FIG> promote maximum energy capture and transfer, but other orientations may achieve similar results. For example, two coil pipes <NUM> could be oriented in a vertical direction along a single wall of the masonry heater <NUM>. Coil pipes <NUM> may also be located in other portions of the masonry heater <NUM>, such as in a downdraft channel or in a secondary heating chamber <NUM> such as the oven, but such placements may not capture the same amount of heat and power per coil pipe <NUM> as coil pipes <NUM> placed in the firebox <NUM> of the masonry heater <NUM>.

<FIG> shows a typical coil pipe <NUM> that is installed in the firebox <NUM> of a masonry heater <NUM>, such as the firebox <NUM> illustrated in <FIG>. Water is typically used as the liquid in the coil pipes, but other liquids such as glycol may be used to achieve similar effects. Water is used to achieve uniformity in the masonry heater <NUM> (primary) side and the external heating device <NUM> (secondary) side. In a typical installation, the length that the coil pipe <NUM> extends into the firebox <NUM> is approximately <NUM> inches (<NUM>), while the coiled part of the pipe is approximately <NUM> inches (<NUM>) of that length. The width of the coil pipe <NUM> in a horizontal direction of the masonry heater <NUM> is approximately <NUM> inches (<NUM>). The diameter of the coil pipe <NUM> is approximately <NUM> inches (<NUM>). The total length of a coil pipe <NUM> typically installed in a heat transfer apparatus is approximately <NUM> feet (<NUM>), which ensures that the liquid in the coil pipe <NUM> will have sufficient exposure to heat in the firebox <NUM> to maximize the temperature of the liquid without vaporizing the liquid. Where two coil pipes <NUM> are installed in the firebox <NUM> in a horizontal manner, as illustrated in <FIG>, the total length of coil pipes <NUM> exposed to the heat of the firebox <NUM> is <NUM> feet (<NUM>).

The length of the coil pipe <NUM> exposed to heat is a critical factor to the overall efficiency and safety of the heat transfer apparatus. If the length of exposed coil pipe <NUM> is too short, the amount of power extracted from the masonry heater <NUM> is not maximized. On the other hand, if the length of exposed coil pipe <NUM> in the firebox <NUM> is too long, the liquid in the coil pipe <NUM> will vaporize which may damage the heat transfer apparatus or cause injury to the operator. The dimensions of the coil pipes <NUM> require only a small volume of liquid to achieve safe and efficient transfer of heat. Typically, only about one-quarter to one-third of a gallon (<NUM> -<NUM>ℓ) of liquid is used in a two pipe coil system. In the event of failure due to power outage, a Temperature and Pressure relief valve (TxP valve <NUM>) will dump liquid from the heat transfer apparatus through the drain <NUM> if the temperature and/or pressure of the liquid becomes too high, but it is preferable that only a small volume of liquid is contained in the system to prevent injury to persons or damage to the system. Stainless steel pipes are preferred for the coil pipes, which are fairly inexpensive, yet can withstand <NUM>°F (<NUM>) temperatures and <NUM>,<NUM> pounds (<NUM> kPa) of pressure per square inch (<NUM> kPa). Other materials may be used for the coil pipes, as long as the materials can similarly withstand high temperatures and pressures.

<FIG> depicts a schematic view of a portion of a heat transfer apparatus and a portion of a heat transfer system. Sensor S1 is the first temperature sensor <NUM> which extends within the firebox <NUM> in the coil pipe, and is connected to an input of a controller <NUM>. A liquid circulation pump <NUM> circulates heated liquid from the coil pipe <NUM> in the masonry heater <NUM> to the external heating device <NUM> when the controller <NUM> detects that the temperature measured by the sensor S1 is equal to or greater than a predetermined temperature threshold. The predetermined temperature threshold should be approximately <NUM>°F (<NUM>). The system will enter thermal runaway if the predetermined temperature threshold is set too high above <NUM>°F (<NUM>). Conversely, if the predetermined temperature threshold is set below <NUM>°F (<NUM>) by a significant amount, the liquid circulation pump <NUM> will continuously circulate the liquid after firing, needlessly wasting energy and increasing the cost of operation.

Temperature sensor S2 (<NUM>), which is connected to an input of the controller <NUM>, detects a temperature of the liquid flowing to the external heating device <NUM> from the masonry heater <NUM> (on the return side <NUM> of the masonry heater <NUM>). Temperature sensor S3 (<NUM>), which is also connected to an input of the controller <NUM>, detects a temperature of liquid returning from the external heating device <NUM> to the masonry heater <NUM> (on the supply side <NUM> of the masonry heater <NUM>). When the temperature measured by the sensor S1 exceeds the temperature threshold, the controller <NUM> directs the liquid circulation pump <NUM> to begin circulating the liquid and controls the flow rate of the liquid circulation pump <NUM> based on a difference between the temperatures measured by the sensors S2 and S3. The flow rate is adjusted to maintain a specified difference in temperature between sensors S2 and S3. For example, if the difference in temperature between sensors S2 and S3 is greater than the specified difference, indicating that the amount of heat being transferred to the external heating device <NUM> is too large, the controller <NUM> will increase the flow rate of the liquid circulation pump <NUM> to reduce the amount of heat transferred to the external heating device <NUM>. If the measured difference in temperature is less than the specified difference, indicating that the amount of heat transferred to the external heating device <NUM> is too small, the controller <NUM> will decrease the flow rate of the liquid circulation pump <NUM> to increase the amount of heat transferred to the external heating device <NUM>. If the difference in temperature is within a specified range of the specified temperature, the controller <NUM> will maintain the current flow rate of the liquid circulation pump <NUM>. The specified temperature differential should be around <NUM>°F (-<NUM>). The specified range and specified temperature settings in the controller <NUM> may be adjusted by a user to accommodate the number of external heating device <NUM> and the type of external heating devices <NUM> connected to the heat transfer apparatus. Once the fuel in the masonry heater <NUM> is exhausted, the temperature of the liquid in the coil pipes <NUM> will lower and eventually the controller <NUM> will stop circulation of the liquid. The controller <NUM> may be a Johnson Controls A419ABC-<NUM> (<NUM> Volt AC), by way of nonlimiting example. The operation of the controller <NUM> and the liquid circulation device are discussed in greater detail later.

<FIG> illustrates a perspective view of two horizontally oriented coil pipes <NUM> connected together as in the embodiment of <FIG>. When the liquid circulation pump <NUM> is off, the masonry heater <NUM> heats the liquid to a predetermined temperature, as detected by the first temperature sensor <NUM>, at which point the controller <NUM> turns the liquid circulation pump <NUM> on and begins circulate the liquid to the external heating device <NUM>. The tip of the first temperature sensor <NUM> should extend well into the masonry heater <NUM> to ensure that a proper temperature reading of the liquid returning from the masonry heater <NUM> is taken. If the first temperature sensor <NUM> does not properly extend into the firebox <NUM>, the heat transfer system may enter thermal runaway potentially damaging the system. The first temperature sensor <NUM> is typically installed in a T-junction at an elbow joint and extending through aperture D at the return side <NUM> of the masonry heater <NUM> for ease of installation and maintenance. Alternatively, the first temperature sensor <NUM> may be installed in the liquid return path of the other coil pipe <NUM> through aperture C without affecting the performance of the heat transfer apparatus, but such an installation is not as easily implemented and does not form part of the invention.

When the liquid circulation pump <NUM> is in a circulation mode, the heat transfer liquid enters the masonry heater <NUM> on supply side <NUM> through coil pipes <NUM> extending through apertures A and B. The heated liquid is then transferred from inside the masonry heater <NUM> through coil pipes <NUM> extending through apertures C and D, and back to the return side <NUM>, where the heated liquid then flows back to the liquid circulation pump <NUM>. As discussed later, an auto-vent valve <NUM> and TxP valve <NUM> may be located on the return side <NUM>.

<FIG> shows a perspective view of two vertically oriented coil pipes <NUM> connected together as in the embodiment of <FIG>. The system works essentially the same as the embodiment shown in <FIG>, except that the supply side <NUM> is located on the bottom side of the masonry heater <NUM>, rather than on a left or right side of the masonry heater <NUM>. In this configuration, it is desirable to have the tip of the first temperature sensor <NUM> extend in a liquid return path of the coil pipe <NUM> closest to the liquid circulation pump <NUM>. As with the configuration of <FIG>, the first temperature sensor <NUM> is preferably installed in the elbow joint on the return side <NUM> of the masonry heater <NUM>.

In <FIG>, the back of the masonry heater <NUM> is illustrated. <FIG> corresponds to the coil pipe <NUM> configuration of <FIG>, where the coil pipes <NUM> are substantially horizontally oriented. When the coil pipes <NUM> are substantially horizontally oriented, the supply side <NUM> of the coil should be located sufficiently lower than the return side <NUM> of the coil pipes <NUM> to ensure that any gas trapped in the coil pipe <NUM> rises to the return side <NUM>, and is purged by the auto-vent valve <NUM>, as described later. The rise yi of the coil pipes <NUM> in the vertical direction is not particularly limited, but the rise in typical installations is around <NUM> inches (<NUM>) to ensure proper evacuation of gas from the lines. <FIG> corresponds to the coil pipe <NUM> configuration of <FIG>, where the coil pipes <NUM> are vertically oriented.

<FIG> illustrates the supply side <NUM> of a heat transfer apparatus and system according to either of <FIG>. As discussed earlier, when the liquid circulation pump <NUM> is operating, liquid is pumped from an external heating device <NUM> back toward the masonry heater <NUM> where it passes through a check valve <NUM>. Check valve <NUM> allows the liquid to flow in only one direction toward the masonry heater <NUM>. Installing a check valve <NUM> in this way serves two functions: first, it ensures a faster response time when the masonry heater <NUM> is heating up by preventing the expanding liquid from back-flowing to the supply side <NUM> of the masonry heater <NUM>. Second, on failure, the check valve <NUM> allows in a small amount of cooler water to cool the coil pipe. A swing check valve <NUM> is preferred as check valve <NUM>, but a ball check valve <NUM>, lift check valve <NUM>, diaphragm check valve <NUM> or other style check valve <NUM> may be used instead. A check valve <NUM> should be selected having a size sufficient to support the flow of liquid through the system, and that can also withstand the temperature of the liquid. The liquid flows from the check valve <NUM> to the supply side <NUM> of the coil pipe <NUM> where the liquid enters the coil pipe <NUM> and the masonry heater <NUM>. <FIG> illustrates that the supply side <NUM> feeds two coil pipes, however, the supply side <NUM> may feed only one coil pipe <NUM> or more than two coil pipes <NUM> without departing from the scope of the heat transfer apparatus and system described herein.

<FIG> illustrates the return side <NUM> of a heat transfer apparatus or heat transfer system according to either of <FIG>. When the liquid circulation pump <NUM> is operating, liquid is pumped from the coil pipes <NUM> inside of the masonry heater <NUM> toward the external heating device <NUM>. The return side <NUM> may also include a hi-point auto-vent valve <NUM> and/or TxP valve <NUM>. The auto-vent valve <NUM> automatically purges any gas stuck in the lines from the system. The auto-vent valve <NUM> may be a Maid-O'-Mist ® <NUM>, by way of non-limiting example. A ball valve <NUM> may be located between the return side <NUM> of the coil pipe <NUM> and the auto-vent valve <NUM> to facilitate the replacement of the auto-vent valve <NUM> without draining liquid from the pipes. The TxP valve <NUM> purges liquid from the system if the temperature of the liquid exceeds a predetermined temperature or if the pressure in the lines exceeds a predetermined pressure. It is important to match the temperature and/or pressure characteristics of the TxP valve <NUM> with the characteristics of the external heating device <NUM>. For example, when the heat transfer system transfers heat to a domestic water system having a hot water heater, if the pressure in the lines exceeds <NUM> pounds per square inch (PSI) (<NUM> kPa), the TxP valve <NUM> will drain liquid from the system until the pressure is reduced to less than <NUM> PSI (<NUM> kPa). When the heat transfer system transfers heat to a hydronic heating system, where liquid is circulated through tubing to radiate heat, the TxP valve <NUM> should drain liquid from the system if the pressure exceeds <NUM> PSI (<NUM> kPa). The TxP valve <NUM> purges liquid from the system into a drain line so that the liquid will be cleanly and safely removed. As a non-limiting example, the TxP valve <NUM> may be a Zurn ® P10000HXL-150C when the external heating device <NUM> is a hot-water heater. When the external heating device <NUM> is a boiler, an Apollo <NUM> valve may be used.

A perspective view of the supply side <NUM> and return side <NUM> is shown in <FIG>. As previously described, check valve <NUM> is located on the supply side <NUM> before the supply side <NUM> forks into separate pipes. On the return side <NUM>, the auto-vent valve <NUM> and ball valve <NUM> are located at the hi-point of the line. The TxP valve <NUM> and drain may also be located on the top part of the return side <NUM>. A T-junction is located on the return side <NUM> at an end of a pipe extending from the masonry heater <NUM>. A first port of the T-junction is connected to the pipe extending from the masonry heater <NUM>, and a second port at a <NUM> degree angle from the first port is connected to piping on the return side <NUM> of the system. At a third port of the T-junction, a sensor sheath housing a first temperature sensor <NUM> is inserted which should extend from the T-junction and into the coil pipe <NUM> within the masonry heater <NUM> to assure accurate temperature measurement of the liquid at or near its hottest point in the masonry heater <NUM>.

<FIG> shows a sectional view of the return side <NUM> of the heat transfer apparatus. The TxP valve <NUM> and auto-vent valve <NUM> are located on a top portion of the return side <NUM>. Piping extends in a direction orthogonal to the top portion to extend into the masonry heater <NUM>. The T-junction is located on the bottom portion in <FIG>, and the first port and third port extend coaxially, while the second port extends in a direction orthogonal to the first and the third port. The liquid returning from the coil pipe <NUM> within the masonry heater <NUM> travels through both the top portion and a lower portion, past the auto-vent valve <NUM>, and to the masonry heater <NUM> and liquid circulation pump <NUM>.

Referring to <FIG>, a threaded pipe is screwed into a fitting <NUM>, which is then inserted and bonded in the third port of the T-junction <NUM>. A sensor sheath <NUM> housing the first temperature sensor S1 is inserted in the first port of the T-junction <NUM>. The first temperature sensor <NUM> should be located as close to the tip of the sensor sheath <NUM> as possible. A flush bushing <NUM> is installed at the base of the sensor sheath <NUM> to seal the T-junction <NUM>. The sensor sheath <NUM> should be long enough to extend through the wall of the masonry heater <NUM> and into the firebox <NUM>. When the liquid circulation pump <NUM> is operating, liquid flows from the coil pipe <NUM> inside the masonry heater <NUM> around the sensor sheath <NUM> in a liquid return path of the coil pipe, and out of the second port of the T-junction <NUM> toward the external heating device <NUM>. In typical installations, the threaded pipe, the fitting, and the T-junction are <NUM> inches in diameter, whereas the sensor sheath <NUM> is slightly smaller at about <NUM> inches in diameter to allow flow of the liquid in the return path of the coil pipe.

<FIG> illustrates how the T-junction <NUM>, coil pipe <NUM>, fitting <NUM>, and sensor sheath <NUM> appear in a sectional view on the return side <NUM> when assembled. The coil pipe <NUM> extends from the fitting <NUM>, through the wall of the masonry heater <NUM>, and into the firebox <NUM>, where the coil pipe <NUM> winds back and forth to be exposed to direct heat and flames in the firebox <NUM>. The sensor sheath <NUM>, which houses the first temperature sensor <NUM>, extends from the first port of the T-junction <NUM>, through the T-junction <NUM>, and into the coil pipe <NUM>. The sensor sheath <NUM> and the first temperature sensor <NUM> further extend through a wall of the masonry heater <NUM> and into the firebox <NUM>. In <FIG>, a <NUM>-inch (<NUM>) sensor sheath is illustrated, which extends through a <NUM> inch (<NUM>) wall <NUM> of the masonry heater <NUM>, and <NUM>-<NUM> inches (<NUM> - <NUM>) of the sensor sheath extend into the firebox <NUM> so that the sensor S1 is exposed to liquid at or near its hottest point in the firebox <NUM>.

Referring back to <FIG>, sensor S1 (in the sensor sheath <NUM>) is connected to an input of a controller <NUM>. The controller <NUM> may be a Johnson Controls model A419ABC-<NUM>, by way of non-limiting example. The controller <NUM> may be programmed to turn the liquid circulation pump <NUM> on/off based on the temperature measured by the sensor S1 in the firebox <NUM>. When the controller <NUM> operates the liquid circulation pump <NUM> to circulate the liquid, the controller <NUM> varies the flow rate of the liquid circulation pump <NUM> based on how much heat is transferred to the external heating device <NUM>. Specifically and as described above, a sensor S2 on the return side <NUM> of the coil pipes <NUM> measures the temperature of the heated liquid being supplied to the external heating device <NUM>. Sensor S3 on the supply side <NUM> of the coil pipes <NUM> measures the temperature of the heated liquid returning from the external heating device <NUM>. The controller <NUM> determines a difference between the temperatures measured by the sensors S2 and S3, and adjusts the flow rate of the liquid circulation pump <NUM> based on the measured temperature difference between sensors S2 and S3 to achieve a target temperature difference. In one application described later, the target temperature difference may be <NUM>°F (-<NUM>). The target temperature difference is the amount of heat transferred from the masonry heater <NUM> to the external heating device <NUM>. Placing the sensors S2 and S3 close to the output of the heat transfer apparatus, and close to the external heating device <NUM>, enables an accurate measurement of the heat actually transferred to the external heating device <NUM>. On the other hand, if the sensors S2 and S3 were placed closer to the masonry heater <NUM>, the measured temperature difference would also measure the amount of heat lost in the piping between the masonry heater <NUM> and the external heating device <NUM>, leading to an inaccurate measurement of how much heat is actually transferred to the external heating device <NUM>. Although the liquid circulation pump <NUM> is disposed on the return side <NUM> of the coil pipes <NUM> in <FIG>, the liquid circulation pump <NUM> may be placed on the supply side <NUM> of the coil pipes <NUM> without adversely affecting the performance of the heat transfer apparatus. In a power outage, the masonry heater <NUM> will continue to heat the liquid while the liquid circulation pump <NUM> cannot transfer heat. The TxP valve <NUM> will prevent the liquid in the heat transfer apparatus from vaporizing and damaging the piping during a power outage. A battery back-up <NUM> may be installed on the controller <NUM> and the liquid circulation pump <NUM> to properly circulate the heated liquid and prevent the TxP valve <NUM> from purging liquid from the system during a power outage. A battery back-up <NUM> (not illustrated) may also be installed on the secondary side of the external heating device <NUM> to allow the system to properly dump heat in the event of a power outage.

<FIG> illustrates the electrical connections of the controller <NUM>. Sensor S1 is connected to input In1 of the controller <NUM>, while sensors S2 and S3 are connected to inputs In2 and In3, respectively, of the controller <NUM>. The controller <NUM> reads a temperature from sensor S1 and, based on whether the temperature is equal to or greater than a predetermined temperature threshold, controls whether the liquid circulation pump <NUM> circulates liquid through the system. An output of the controller <NUM> is connected to the liquid circulation pump <NUM>, either directly or through an intermediate device. The controller <NUM> may be configured to output a digital HI/LO signal directing the liquid circulation pump <NUM> to circulate liquid. Alternatively, the controller <NUM> may be configured to generate an analog signal (e.g., 24V AC signal at <NUM>) directing the liquid circulation pump <NUM> to circulate liquid. An intermediate device (not illustrated) may be used which generates a specified analog signal when the HI/LO output of the controller <NUM> outputs a HI digital signal. For example, the controller <NUM> may output a +5V digital signal to a D/A converter, which outputs a 24V AC signal to the liquid circulation pump <NUM>, causing the liquid circulation pump <NUM> to circulate liquid through the system. These examples are intended to be non-limiting descriptions of the myriad ways in which the controller <NUM> may control the liquid circulation pump <NUM>.

The controller <NUM> may also determine the difference between the sensors S2 and S3 and output a signal directing the liquid circulation pump <NUM> to circulate liquid at a particular flow rate based on the measured difference. Alternatively, sensors S2 and S3 may be connected directly to the liquid circulation pump <NUM>, which may be configured to control the flow rate based on the temperature difference measured between sensors S2 and S3. The liquid circulation pump <NUM> may be a Taco variable speed delta-T <NUM> ® circulator or a Taco HEC-<NUM> BumbleBee ®, by way of non-limiting example.

Referring to <FIG>, the external heating device <NUM> may be a boiler <NUM> in which a liquid is heated or vaporized. The controller <NUM> and/or liquid circulation pump <NUM> are configured to transfer a given amount of heat to the boiler <NUM> based on the heat required by the boiler <NUM> to operate.

Referring to <FIG>, the external heating device <NUM> may be a liquid heater <NUM>, such as a hot-water heater. The heated liquid from the masonry heater <NUM> is circulated into the liquid heater <NUM>, where the heated liquid flows over a plate heat exchanger <NUM>. The plate heat exchanger <NUM> transfers heat from the heated liquid to a secondary liquid, which may be water or glycol, for example. The secondary liquid may be used as domestic heated water and may be used to provide radiant heat to a building. The radiant zone <NUM> and associated devices function as an over-heat thermal dump apparatus, which dumps heat from the masonry heater and liquid heater <NUM> when the temperature of the heated liquid is too high. Because masonry heaters <NUM> generate very large amounts of heat, it is sometimes necessary to dump excess heat from the system to prevent vaporization of liquid in the system or damage to the system. The radiant zone <NUM> may be installed in a room or several rooms to provide heat thereto. The radiant zone <NUM> may also be installed in a cooler area of a building, such as a garage, where heat may be more rapidly dumped than an interior room of a building. The liquid heater <NUM> in <FIG> may be an HTP Versa-Hydro Combination Hydronic Appliance, by way of non-limiting example.

Radiant heat zone <NUM> radiates heat from heated liquid to an area in a house or building. Zone valve <NUM> opens and closes to allow liquid to flow from the liquid heater <NUM> to radiant zone <NUM> when a predetermined control signal is received on control line V11. Liquid circulation pump <NUM> controls the flow rate of the liquid flowing from the liquid heater to the radiant zone <NUM> based on the control signal received on control line V12. Although zone valve <NUM> and liquid circulation pump <NUM> are both illustrated in <FIG>, it may be necessary to use only one or the other depending on the type of system. Temperature sensor S4 <NUM> measures the temperature T<NUM> of the liquid in the liquid heater <NUM>. Temperature sensor S5 <NUM> and temperature sensor S6 <NUM> measure the temperature of the liquid flowing to and from the radiant heat zone <NUM>, respectively. Temperature sensor S7 <NUM> measures the ambient air temperature of the area in which the radiant heat zone <NUM> is installed. Although only a single radiant heat zone <NUM> is illustrated in <FIG>, more than one radiant heat zone may be connected to the liquid heater <NUM> to selectively radiate heated liquid distributed from liquid heater <NUM>. The radiant heat zones are typically connected in parallel to the liquid heater <NUM>, but may be connected in series depending on installation demands, such as the building layout. A thermostat (not shown) controls each radiant heat zone.

<FIG> illustrates the control configuration of a single radiant heat zone. A user can set the temperature for the area corresponding to the radiant heat zone <NUM> using control panel <NUM>. The thermostat <NUM> receives the desired temperature setting from the control panel <NUM> and the ambient air temperature measured by sensor S7. Thermostat <NUM> may read the temperature T<NUM> of the heated second liquid from the sensor S4 in the liquid heater to better control the amount of heat radiated from the radiant heat zone <NUM>, although it is not necessary for the thermostat <NUM> to monitor the sensor S4. Thermostat <NUM> may also measure the temperature differential (T5 - T6) between sensors S5 and S6 to measure the amount of heat actually radiated from the radiant heat zone <NUM>. Sensors S5 and S6 should be placed as close to the radiant heat zone <NUM> to accurately measure the amount of heat actually transferred to and radiated from the radiant heat zone <NUM>. The thermostat <NUM> generates a control signal containing information including whether the zone valve <NUM> should be open or closed, and/or the flow rate of the liquid circulation pump <NUM> based on the temperatures measured by sensors S4, S5, S6, and/or S7, as well as the desired temperature setting from the control panel <NUM>. The controller <NUM> acts as a relay bypass to bypass the thermostat <NUM> control when the temperature of the liquid in the liquid heater <NUM> exceeds a predetermined temperature threshold. In this configuration, control of the radiant heat zones is achieved electrically, without the need to divert the heated liquid to a different channel or radiant zone. The controller <NUM> may be configured operate the zone valve <NUM> and/or liquid circulation pump <NUM> to dump heat between <NUM>°F (<NUM>) and <NUM>°F (<NUM>), well-before the liquid is vaporized.

The controller <NUM> outputs a zone valve control signal and/or a circulation pump control signal based on the control signal received from the thermostat <NUM>. The controller <NUM> may be configured to generate the zone valve control signal and/or the circulation pump control signal based on a control signal sent from the thermostat <NUM>, which includes the desired temperature setting and the temperature measured by sensor S7 near the radiant heat zone <NUM>. When the controller <NUM> determines that the temperature T4 measured by sensor S4 exceeds the predetermined temperature, the controller <NUM> bypasses the control signal sent from the thermostat and begins dumping heat from the liquid heater <NUM> to the radiant heat zone <NUM>. That is, the controller <NUM> enters a relay bypass mode in which heat is dumped from the liquid heater <NUM> to the radiant heat zone to prevent thermal runaway when the controller <NUM> determines that the temperature measured by sensor S4 exceeds the predetermined temperature. In the relay bypass mode, the controller <NUM> controls the zone valve <NUM> and/or the liquid circulation pump <NUM> independently of the thermostat <NUM> and the desired temperature setting until the radiant heat zone <NUM> dumps enough heat from the liquid heater <NUM> to ensure that the system is not in danger of entering thermal runaway. The controller <NUM> may adjust the flow rate of the circulation pump <NUM> based on the temperature differential (T<NUM> - T<NUM>) of the temperatures measured by sensors S5 and S6 to dump enough heat to efficiently and effectively reduce the temperature of the heated liquid in the liquid heater. The controller <NUM> will continue to monitor the temperature T<NUM> measured by the sensor S4 and operate in the relay bypass mode until the temperature T<NUM> measured by the sensor S4 is less than the predetermined temperature. Once the temperature T<NUM> returns to an acceptable level, the controller <NUM> returns to a normal operating mode wherein the controller outputs a zone valve control signal and/or a circulation pump control signal based on a control signal supplied by the thermostat <NUM>.

When multiple radiant heat zones <NUM> are connected to the liquid heater <NUM>, thermal dump control is separately performed for each zone. The control configuration for multiple radiant heat zones is illustrated in <FIG>. As previously discussed, the radiant heat zones are typically connected in parallel to the liquid heater <NUM>, but may be connected in series depending on the building in which the system is installed. Each radiant heat zone may be a different size and therefore may each radiate and dump heat at different rates and may each comprise the elements illustrated in <FIG>. Each radiant heat zone has a corresponding control panel <NUM>-N and thermostat <NUM>-N, where N is an integer ranging from <NUM> to the total number of radiant heat zones installed in the system. A relay bypass RN1, RN2 is installed for each zone valve <NUM> and circulation pump <NUM>, respectively. The relay bypasses RN1, RN2 isolate the thermostats of each zone from one another. Relay bypass R11 has a first input connected to the Zone <NUM> ON/OFF signal of thermostat <NUM>-<NUM>, a second input connected to the Zone <NUM> ON/OFF signal of controller <NUM>, and a third input connected to the Zone <NUM> Bypass signal of controller <NUM>. Relay bypass R12 has a first input connected to the Zone <NUM> flow rate signal of thermostat <NUM>-<NUM>, a second input connected to the Zone <NUM> flow rate signal of controller <NUM>, and a third input connected to the Zone <NUM> Bypass signal of controller <NUM>. Every relay bypass RN1, RN2 is connected in a similar manner as R11 and R12, respectively.

When the controller <NUM> determines that the temperature T<NUM> measured by sensor S4 exceeds the predetermined temperature, the controller selects one or more of the radiant heat zones to bypass. The controller <NUM> is configured to separately and selectively bypass the thermostat <NUM>-N of each zone and select which radiant heat zone to control. The controller <NUM> may select radiant heat zones based on the rate at which the temperature T<NUM> measured by sensor S4 is increasing or the rate at which each zone is capable of dumping heat. The controller <NUM> sends a relay bypass signal to the relay bypass RN1, RN2 of the selected zone(s), causing the selected relay bypass RN1, RN2 to output a signal from the controller <NUM> instead of the corresponding thermostat <NUM>-N. For example, the relay bypasses R11 and R12 of zone <NUM> normally output the zone <NUM> ON/OFF signal and zone <NUM> flow rate signal, respectively, from thermostat <NUM>-<NUM>. When the controller <NUM> determines temperature T<NUM> exceeds the predetermined temperature and selects zone <NUM> to bypass, controller <NUM> outputs a bypass control signal to relay bypass R11 and R12, causing relay bypass R11 and R12 to output control signals from the controller <NUM> instead of the thermostat <NUM>-<NUM>. The controller <NUM> may bypass and control the other thermal dump zones in a manner similar to zone <NUM>.

Referring to <FIG>, an over-heat thermal dump apparatus <NUM> may be connected to the heat transfer apparatus and heat transfer system to dump excess heat from the system. In normal operation, the second liquid in the liquid heater <NUM> is may be directed to a domestic liquid outlet <NUM>, for example. As previously discussed, it is sometimes necessary to dump excess heat from the system to prevent vaporization of liquid in the system or damage to the system because masonry heaters <NUM> generate very large amounts of heat. In the configuration shown in <FIG>, the thermal dump apparatus <NUM> is connected to the liquid heater <NUM> and is equipped with a relay bypass <NUM> to direct the heated secondary liquid to a thermal dump zone (radiant heat zones <NUM>) where excess heat may be rapidly dumped. In this configuration, when the secondary liquid in the liquid heater <NUM> reaches a predetermined temperature, as measured by temperature sensor <NUM> (S4), at which there is a danger of the secondary liquid being vaporized, the relay bypass <NUM> is activated, which transfers the heated second liquid to a radiant zone <NUM> to dump heat. The radiant zone <NUM> may be coil heating pipes distributed through the floor or walls of a building, efficiently using the excess heat in areas of a building that are remotely located away from the masonry heater <NUM>.

In normal operation, when the temperature of the second liquid is below the predetermined temperature, the second liquid flows from the liquid heater <NUM> through the liquid circulation pump <NUM>, and directly through the relay bypass <NUM>. When the temperature of the second liquid exceeds the predetermined temperature, the controller <NUM> operates the relay bypass <NUM> to direct the second liquid toward the radiant heat zones <NUM>. The controller <NUM> may be configured operate the relay bypass <NUM> to dump heat between <NUM>°F (<NUM>) and <NUM>°F (<NUM>), well-before the liquid is vaporized. The radiant zone <NUM> may be installed in a cooler area of a building, such as a garage, where heat may be more rapidly dumped than an interior room of a building. The liquid heater <NUM> in <FIG> may be an HTP Versa-Hydro Combination Hydronic Appliance, by way of non-limiting example.

In <FIG>, temperature sensors S4, S5 and S6 are located on a supply side <NUM> and return side <NUM> of the relay bypass <NUM> to measure the temperature differential between sensors S5 and S6, which indicates an amount of heat being dumped to a radiant zone <NUM>. The heat measured on the supply side <NUM> by sensor <NUM> (S5) should be higher than the ambient air temperature, but much lower than the boiling point of the second liquid used. The liquid circulation pump <NUM> controls the flow rate of the liquid in the radiant heat zones <NUM> based on the measured heat differential between sensors S4 and S5. The controller <NUM> may direct the liquid circulation pump <NUM> to stop controlling the flow of fluid in a thermal dump mode, allowing the liquid circulation pump <NUM> to control the flow rate. Alternatively, the controller <NUM> may control the liquid circulation pump <NUM> and liquid circulation pump <NUM> in concert. Once the temperature measured by the sensor S4 falls below the predetermined temperature, the controller operates the relay bypass <NUM> to pass liquid directly to the domestic liquid outlet <NUM> and directs the liquid circulation pump <NUM> to stop circulation of the second liquid.

The flow rate is controlled to achieve an ideal amount of heat dumped based on the size of the radiant zones. For example, a <NUM>°F (-<NUM>) differential between sensors S5 and S6 may be selected, such that the flow rate is increased when the amount of heat dumped is greater than <NUM>°F (-<NUM>), and the flow rate is decreased when the amount of heat dumped is less than <NUM>°F (-<NUM>). It is recommended to maintain the return side <NUM> of the radiant zone at around <NUM>°F (<NUM>), and the liquid in the supply side <NUM> so it does not exceed <NUM>°F (<NUM>) to ensure that the system does not enter thermal runaway. Control of heat transfer to the thermal dump zones is discussed in further detail later. Although the over-heat thermal dump control is described with reference to a liquid heater <NUM>, the over-heat thermal dump control may be connected to any other external heating device <NUM> to moderate temperature in the system. The controller for the thermal dump control may be a Johnson Controls A419GBF-<NUM> (<NUM> Volt DC), by way of non-limiting example. A single controller may be used to control circulation of liquid within the liquid heater <NUM>, the thermal dump zones <NUM>, and in the coil pipes <NUM>.

<FIG> shows a configuration where the heated liquid from the masonry heater <NUM> is transferred to a duct coil <NUM>. The duct coil <NUM> may be used in an HVAC system to distribute heat throughout a building via blown air.

Referring to <FIG>, a low-loss header <NUM> may be installed to provide hydraulic isolation between the masonry heater <NUM> side of the heat transfer apparatus and heat transfer system. The low loss header <NUM> may be connected to one or more external heating devices <NUM>, or may be connected to radiant heating, as shown in <FIG>. Another liquid circulation pump <NUM> may be connected to the secondary side of the low-loss header <NUM> to control the flow rate of liquid on the secondary side relative to the primary side (i.e. the masonry heater <NUM> side).

Referring to <FIG>, heated liquid from the masonry heater <NUM> may be ported into the element ports of a hot water heater <NUM>, where the heated liquid from the masonry heater <NUM> may heat domestic water via a heat exchanger (not illustrated). The heated water from the hot-water heater may then further be used in an oil heater <NUM>, such as a Toyotomi oil miser, greatly increasing the efficiency of the oil heater. As previously discussed, a thermal dump apparatus <NUM> may be installed on the liquid heater <NUM> to dump heat when the heat of the liquid in the liquid heater <NUM> exceeds a predetermined temperature.

<FIG> illustrates a flow chart describing the functionality of the controller <NUM> and the liquid circulation pump. In step S100, the temperature T<NUM> of sensor S1 in the coil pipe <NUM> within the masonry heater <NUM> is measured. If the temperature T<NUM> is less than a first predetermined temperature threshold (in step S102), the process proceeds back to step S1 where the temperature T<NUM> is measured again. If, on the other hand, the temperature T<NUM> is greater than or equal to a first predetermined temperature threshold (in step S102), the liquid circulation pump is activated (S104), and the liquid circulation pump begins to circulate liquid in the system. As step S106, the temperature T<NUM> is measured again, and if the temperature T<NUM> is less than the first predetermined temperature threshold at step S110, the first liquid circulation pump is turned off in step S112 and the process begins again at step S100. If the temperature T<NUM> remains equal to or greater than the first predetermined temperature threshold, the process proceeds to step S114. At step S122, the temperatures T<NUM> and T<NUM> of sensor S2 and sensor S3, respectively, are measured. At step S116, the difference (T<NUM> - T<NUM>) is determined, and if the difference (T<NUM> - T<NUM>) is greater than or equal to a predetermined temperature difference, the flow rate of the liquid circulation pump is increased (step S122). When the temperature is greater than the predetermined temperature difference, then too much heat is being transferred to the external heating device <NUM>, so the flow rate is increased to decrease the amount of heat transferred to the external heating device <NUM>. If, in step S116, the difference (T<NUM> - T<NUM>) is less than the predetermined temperature difference, then the flow rate is decreased to increase the amount of heat transferred (S12). Alternatively, the flow rate may be kept constant if the difference (T<NUM> - T<NUM>) is within an acceptable predetermined range.

Referring to <FIG>, a process for dumping excess heat is illustrated using the thermal dump apparatus illustrated in <FIG>. In step S200, the temperature of sensor S1 is measured (in conjunction with the process discussed with respect to <FIG>), and when the temperature exceeds the first predetermined temperature threshold, the process proceeds to step S204 to measure the temperature of the second liquid in the liquid heater <NUM>. When the temperature of the liquid measured in the external heating device <NUM> exceeds a third temperature threshold in step S206, the process proceeds to step S208, where a relay bypass <NUM> is operated to dump excess heat to radiant heating zones <NUM>. If the temperature measured by sensor S4 is less than the third temperature threshold in step <NUM>, the process returns to step S200.

After the relay bypass <NUM> begins directing the second liquid to the thermal dump zones <NUM>, the temperature of the sensor S4 is again measured in step S210. In step S212, when the measured temperature of the second liquid falls below the third temperature threshold, the relay bypass <NUM> directs the second liquid away from the thermal dump zones <NUM> and returns to the normal operation mode (step S214). When the temperature T<NUM> measured by sensor S4 is greater than the third temperature threshold, the liquid circulation pump <NUM> circulates the second liquid to the thermal dump zones and the temperatures T<NUM> and T<NUM> of the second fluid at sensors S5 and S6, respectively, are measured (step S216). At step <NUM> the difference (T<NUM> - T<NUM>) is determined, and when the difference (T<NUM> - T<NUM>) is within a predetermined temperature range (<NUM>th temperature threshold), the liquid circulation pump <NUM> maintains the current flow rate. The heat of the liquid in the thermal dump zones should be maintained to 165oF-<NUM>°F (<NUM> - <NUM>), such that (T5 - T6) should be approximately <NUM>°F (-<NUM>). It may be necessary to add more radiant heating zones if the temperature in the radiant zones exceeds <NUM>°F (<NUM>) to keep the temperatures in the radiant zones comfortable. If the difference (T5 - T6) exceeds the predetermined temperature range, the flow rate of the liquid transferred to the radiant heating zones is increased. If the difference (T5 - T6) is within the predetermined temperature range, the flow rate is maintained in step S220 (or decreased where necessary to maintain an acceptable radiant temperature). Once enough heat is dumped from the secondary side of the external heating device <NUM> such that the temperature of the liquid in the external heating device <NUM> is less than the second temperature threshold, the relay bypass is turned off and the second liquid circulation pump stops pumping liquid to the dump zones (S214).

Referring to <FIG>, the previously-described heat transfer system may additionally include other heat sources to transfer heat to the external heating device <NUM>, including a geothermal heat source <NUM>, a solar heat source <NUM>, and/or a backup heat source <NUM>. The solar heat source <NUM> may be a solar panel that generates electricity to power a heating element that heats the heat transfer liquid passing through a reservoir or pipe connected to the heating element. The solar heat source <NUM> may be tubing or a container through which the heat transfer liquid flows that passively absorbs heat from the sun. The backup heat <NUM> source may be a gas, oil or electric heat source that generates heat when the other heat sources are not producing the desired amount of heat. The geothermal heat source <NUM> may be buried in the ground to absorb heat directly from the earth, or may absorb heat directly from the air on a hot summer day. Other known heat sources may be connected to the heat transfer system to achieve similar results.

The heat sources have a supply line and a return line each connected to closely spaced T-junctions placed in series around a primary loop <NUM>. A liquid circulation pump <NUM>, <NUM>, <NUM> is disposed on at least one of the supply line and the return line of each of the heat sources to transfer heat by circulating a heat transfer liquid between the primary loop <NUM> and each of the heat sources. A liquid circulation pump <NUM> is also disposed in the primary loop <NUM> to circulate the heat transfer liquid in the primary loop <NUM> and uniformly distribute the heat transfer liquid between the heat sources.

At least one other heat source is connected to the primary loop <NUM> via a supply line and a return line to receive heat from the primary loop <NUM>. Although a liquid heater <NUM> is illustrated in <FIG>, the external heat device <NUM> may be one or more of a boiler, a low-loss header, or a duct coil, as previously described. In at least one of the supply line and return line of the external heating device <NUM>, a liquid circulation pump <NUM> is installed to transfer heat toward the external heating device <NUM> by circulating liquid from the primary loop <NUM> to the external heating device <NUM>. A pump <NUM> is installed between the liquid circulation pump <NUM> and the external heating device <NUM>. The portion of the system on the primary loop side is a primary side while the portion of the system on the external heating device <NUM> side is a secondary side. The pump <NUM> prevents flow on the primary side from interfering with flow on the secondary side. On the secondary side, a liquid circulation pump <NUM> may be used to control flow on the secondary side. As previously described, a plate heat exchanger <NUM> in the liquid heater <NUM> transfers heat from the heat transfer liquid to a second liquid. An over-heat thermal dump control, as discussed with respect to <FIG>, may be connected on the secondary side to dump excess heat from the secondary side.

Each of the liquid circulation pumps <NUM>, <NUM>, <NUM> controls the flow of the heat transfer liquid in the primary loop <NUM> to and from each of the respective heat sources. Sensors S2-S15 should be placed as close to the T-junctions as possible to measure the heat transfer to the primary loop from each of the heat sources. A primary circulation pump <NUM> is disposed in the primary loop to control flow of the heat transfer liquid around the primary loop <NUM>. The primary circulation pump <NUM> may be connected to a controller <NUM> that controls whether the primary circulation pump <NUM> circulates the heat transfer liquid around the primary loop <NUM>, as well as the flow rate of the heat transfer liquid around the primary loop <NUM>. The other liquid circulation pumps <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be also connected to the controller <NUM> to control the amount of heat transferred to the external heating device <NUM>. The controller <NUM> may be preprogrammed to transfer a specific amount of heat to the external heating device <NUM> by controlling the primary circulation pump <NUM> and other liquid circulation pumps <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> in concert. Specifically, the controller controls whether each of the liquid circulation pumps circulate liquid through the masonry heater <NUM> and/or each of the other heat sources, as well as the flow rates of the liquid in the primary loop <NUM> and/or the heat sources through which the liquid is flowing. The controller <NUM> may also control the flow rate of liquid on the secondary side and the thermal dump control on the secondary side when necessary. When the masonry heater <NUM> is fired, it may not be necessary to transfer heat from any of the other heat sources to the external heating device <NUM>. In the summer, when the weather may be too hot to fire the masonry heater <NUM>, heat from the solar heat source and geothermal heat source may be transferred to the external heating device <NUM> without circulating liquid to the masonry heater <NUM>. In this configuration, the heat transfer system may efficiently transfer heat to one or several external heating devices <NUM> year round, greatly reducing the cost of heating.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from this invention and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of this invention. Furthermore, it is to be understood that the invention is solely defined by the appended claims. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.).

Claim 1:
A heat transfer apparatus comprising a masonry heater (<NUM>) with a firebox (<NUM>) including a wall (<NUM>), and a coil pipe (<NUM>) extending into the firebox (<NUM>) of the masonry heater (<NUM>) through a first aperture (B) in the wall (<NUM>) of the firebox and exiting through a second aperture (A) in the wall (<NUM>) of the firebox (<NUM>), the coil pipe (<NUM>) winding back and forth in the firebox (<NUM>) and being disposed so as to be exposed to fire in the firebox (<NUM>), wherein a heat transfer liquid enters the coil pipe (<NUM>) from a supply side of the coil pipe (<NUM>) at the first aperture(B) and the heat transfer liquid exits the coil pipe (<NUM>) from a return side of the coil pipe (<NUM>) at the second aperture (A);
a first sensor (<NUM>) configured to detect a temperature of the heat transfer liquid in a liquid return path, on the return side of the coil pipe (<NUM>);
a circulation pump (<NUM>) configured to transfer the heat transfer liquid from the return path to an output of the heat transfer apparatus when the circulation pump (<NUM>) is circulating the liquid, and stopping transfer of the heat transfer liquid to the output of the heat transfer apparatus when the circulation pump (<NUM>) is not circulating the heat transfer liquid; and
a controller (<NUM>) configured to control whether the circulation pump (<NUM>) circulates the heat transfer liquid based on a temperature detected by the first sensor (<NUM>); and
characterized by
a T-junction (<NUM>) disposed on the outside of the masonry heater (<NUM>) on the return side of the coil pipe (<NUM>); and
a sensor sheath (<NUM>) housing the first sensor (<NUM>),
wherein the sensor sheath (<NUM>) is inserted into a first port of the T-junction (<NUM>) and extends from the first port of the T-junction (<NUM>) through the T-junction (<NUM>) into the coil pipe (<NUM>) via a third port of the T-junction (<NUM>), the sensor sheath (<NUM>) extending through the wall (<NUM>) of the masonry heater (<NUM>) into the firebox (<NUM>) such that the first sensor (<NUM>) is located within the firebox (<NUM>) in the liquid return path and such that when the circulation pump (<NUM>) is operating, liquid flows from the coil pipe (<NUM>) inside the masonry heater (<NUM>) around the sensor sheath (<NUM>) and out of a second port of the T-junction (<NUM>) toward an external heating device (<NUM>).