Abstract:
Systems and methods for preventing water from freezing in a spa or hot tub featuring a spa pack having a pump, heater and controller connected to a spa power supply through a ground fault circuit interrupter. A sensor is used to monitor an operating condition of the spa pack that is initially electrically connected to the spa power supply in order to activate at least one freeze prevention device if the operating condition of the spa pack changes due to electrical disconnection from the spa power supply by the ground fault circuit interrupter. The freeze prevention device features a heater, a circulating pump or both, and keeps water in the tub and the piping associated therewith from freezing. A switching arrangement is provided for deactivating the system outside the winter season when freeze protection is not required.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit under 35 U.S.C. 119 of Canadian Patent Application Serial No. 2,696,803, filed Mar. 17, 2010. 
     FIELD OF THE INVENTION 
     The present invention relates generally to spas, and more particularly to spas in climates having cold weather seasons during which unheated water in the spa may freeze and cause damage. 
     BACKGROUND OF THE INVENTION 
     It is well known to use spas, also commonly referred to as hot tubs, outdoors during cold weather seasons to provide an enjoyable experience using the contrast of the cold ambient outdoor temperature and the heated water of the spa. However, a known problem with winter use of an outdoor spa is that if power is cut off to the water circulating pump and heater of the spa, the water in the tub and in the pipework connected thereto can easily freeze if ambient conditions are cold enough, and the expansion of the water as it freezes can cause cracks to form in the tub or pipes, which can lead to leaks when the water thaws and can require costly or time consuming repair or replacement of components or entire systems. 
     The powered components of a spa include a water heater, at least one pump for circulating water through pipes interconnecting the heater and the tub, and a controller operable to control the pump and the heater in response to input from an owner, operator or user of the spa. Collectively, these components are often referred to as a spa pack. The spa pack is typically connected to a power source through a ground fault circuit interrupter (GFCI), which will disconnect electrical communication between the spa pack and the power source if a ground fault is detected in order to remove a potential electrocution hazard. This is problematic during winter use of the spa, in that if the GFCI cuts off the power supply to the spa pack and the hot tub is left unattended, the water can quickly freeze, especially in the circulation pipes, and cause damage to the spa. Operating spas are sometimes left unattended for extended periods of time during the cold weather season, for example by cottage owners who transit back and forth between a rural cottage and an urban environment and leave their cottage spa running between visits during the winter season to prevent freezing. Should the GFCI trip in their absence, they will likely return to find their spa frozen when the next retreat to the cottage. 
     Accordingly, it is desirable to provide freeze protection for spas suing ground fault protected spa packs. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the invention there is provided a freeze prevention system for a spa system having a spa pack including a pump, a water heater and a controller connected to a spa power supply by a ground fault circuit interrupter, the freeze prevention system comprising: 
     a sensor operable to detect electrical disconnection of the spa pack from the spa power supply; and 
     at least one freeze prevention device arranged to activate in response to detection of the electrical disconnection of the spa pack from the spa power supply by the sensor. 
     According to a second aspect of the invention there is provided a spa system having freeze prevention capabilities, the spa system comprising: 
     a spa tub for holding water; 
     a spa pack comprising a pump, a water heater and a controller connected to a spa power supply by a ground fault circuit interrupter, the water heater being connected to the spa tub by piping and the pump being installed on the piping for circulating water between the water heater and the spa tub; 
     a sensor operable to detect electrical disconnection of the spa pack from the spa power supply; and 
     at least one freeze prevention device arranged to activate in response to detection of the electrical disconnection of the spa pack from the spa power supply by the sensor. 
     According to a third aspect of the invention there is provided a method for preventing water from freezing in a spa system having a spa pack including a pump, a water heater and a controller connected to a spa power supply by a ground fault circuit interrupter, the method comprising: 
     (a) monitoring an operating condition of an initially operating spa pack electrically connected to the spa power supply; and 
     (b) activating at least one freeze prevention device if the operating condition of the spa pack changes due to electrical disconnection from the spa power supply by the ground fault circuit interrupter. 
     Preferably the sensor comprises a relay. 
     Preferably the at least one freeze prevention device is arranged for connection to a second power supply distinct from the spa power supply. 
     The second power supply may be of lower voltage than the spa power supply. 
     Preferably the at least freeze prevention device is arranged to connect to a second ground fault circuit interrupter. 
     Preferably the at least one freeze prevention device comprises a heater. 
     The heater may be a space heater sized for receipt within a housing of the spa. 
     Preferably the at least one freeze prevention device comprises an auxiliary pump for use on a circulation line of the spa. 
     The circulation line may comprise the piping on which the pump of the spa pack is installed, the auxiliary pump being installed in parallel with the pump of the spa pack. In this instance, preferably at least one valve is installed between the pump of the spa pack and the auxiliary pump and is arranged to open in response to detection by the sensor of the absence of the electrical connection between the spa power supply and the spa pack. 
     Preferably there is provided an alarm condition indicator arranged to activate in response to detection by the sensor of the absence of the electrical connection between the spa power supply and the spa pack. 
     Preferably there is provided a switch operable to activate and deactivate the sensor. 
     Preferably the switch is used to activate the sensor at the start of a winter season, and deactivate the sensor at the end of the winter season. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings, which illustrate a exemplary embodiment of the present invention: 
         FIG. 1  is a schematic diagram of a first embodiment freeze protection system installed on a spa. 
         FIG. 2  is a schematic diagram of an auxiliary pump installed on an existing circulation line of the spa as part of the first embodiment freeze protection system. 
         FIG. 3  is a schematic diagram of a second embodiment freeze protection system installed on a spa. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically show a spa installation  10  which, in a conventional manner, incorporates a spa pack including a pump and a water heater installed on a circulation line within a housing or enclosure of the tub of the spa, and a control unit installed at the tub enclosure to present a control panel operable by occupants of the tub when in use. The spa back is wired to the two hot lines L 1 , L 2  of a 220V electrical supply  11  via a ground fault circuit interrupter (GFCI) so that the GFCI will trip upon detection of a ground fault in order to interrupt the connection between the power supply and the operating spa pack, this electrical disconnection acting to shut down the previously powered spa pack to remove a potential electrical hazard. 
     The freeze protection system of the present invention ties into this conventional spa pack setup by placing a control relay  20  across the power supply lines L 1 , L 2  in parallel with the spa pack between the GFCI and the spa pack. A double pole single throw switch  22  on opposite sides of the control relay between the lines L 1 , L 2 . This switch  20  is operable to control activation and deactivation of the freeze protection system. At the start of a season or groups of season in which below freezing temperatures are expected and the spa is continuously run to avoid freezing, the switch  22  is closed by an owner or operator of the spa which energizes the control relay by allowing current flow therethrough from the 220 v power supply  14  via the reset or untripped GFCI. The control relay is used as a sensor to monitor the operating condition of the spa pack. Operation of the spa pack is confirmed by current flow through the control relay  20 , but if the GFCI is triggered and accordingly electrically disconnects the spa pack from the power supply  14 , the spa pack ceases to operate and this inactive operational state of the spa pack is reflected by the lack of current flow through the control relay  20  due to the opening of the circuit a the GFCI. Using the relay to detect that the spa pack is no longer operational, and that the spa&#39;s primary water heater and pump in the spa pack are therefore no longer operable to heat and circulate the water in the spa, the system then activates its own freeze prevention devices to keep the water in its liquid state. 
     Still referring to  FIG. 1 , the relay  20  of the first embodiment is provided with five contact sets CR 1 , CR 2 , CR 3 , CR 4 , CR 5  wired to its controlled output circuit. This output circuit is powered by a 120V power supply separate from the 220V power supply used by the spa pack, and features five components wired parallel to one another between the hot and neutral lines of the 120V power supply. Each contact set of the control relay is wired in series with a respective one of the five parallel components. The first contact set CR 1  is normally closed and wired in series with a solenoid valve  24 , the second contact set CR 2  is normally open and wired in series with a normal operation indicator light  26 , the third contact set CR 3  is normally closed and wired in series with a solenoid valve  24  an alarm condition indicator light  28 , the fourth contact set CR 4  is normally closed and wired in series with the motor of an auxiliary pump  30  and the fifth contact set CR 5  is normally closed and wired in series with an auxiliary heater  32 . The solenoid valve, auxiliary pump and auxiliary heater are each protected by a respective fuse in series therewith. Although not shown, the output circuit of the relay incorporates an off switch for selectively connecting and disconnecting the components in this circuit to and from the 120V power supply. Accordingly, switching on and off of the freeze protection system is completed by switching on and off both the input circuit path of the relay, using switch  22  on the higher voltage circuit, and the output circuit path of the relay using the switch on the lower voltage circuit. The switch on the lower voltage circuit may be provided by a circuit breaker at the distribution panel providing the 120V power supply. 
     Turning now to  FIG. 2 , the pump  12  and water heater  13  of the spa pack are installed in series in a normal fashion on a circulation line  14  made up of sections of piping fluidly communicating the spa pack pump  12  and water heater  13  to the tub  15  of the spa. The auxiliary pump  30  of the freeze prevention system is installed on the circulation line  14  in parallel with the primary pump  12  and heater  13  provided by the spa pack. A first primary section of circulation piping  14   a  connecting an outlet of the tub with an inlet of the primary pump  12  has a first auxiliary piping section  34   a  branching of the first primary section  14   a  between the tub  15  and the primary pump  12  to connect to the inlet of the auxiliary pump  30 . From the outlet of the auxiliary pump  30 , a second section  34   b  of auxiliary piping connects to a second primary section of circulation piping  14   b  connecting an outlet of the primary pump  12  with an inlet of the tub  15  at a position along this second primary section  34   b  between the primary heater  13  and the tub  15 . A connecting section  14   c  of the primary piping interconnects the primary pump  12  and heater  13  in series. The solenoid valve  24  is installed on the first auxiliary piping section  34   a  and is biased to normally close this section of piping. 
     When the spa pack is operational, it controls the primary pump  12  and primary water heater  13  in a conventional manner to flow water through the primary circulation line  14 , thereby passing water through the primary water heater  13  to elevate the temperature of the water flowing therethrough back to the tub  15 . During this normal operation, the normally closed solenoid valve  24  closes off the flow into the auxiliary piping  34  and through the auxiliary pump  30  installed thereon. When the switches on the input and output circuits of the freeze prevention system are closed with the spa pack operating at the start of the cold season(s), the control relay is energized by the current running the spa pack from the higher voltage power supply. This energization of the control relay  20  opens the normally closed first contact set CR 1 , and the normally closed solenoid valve  24  is accordingly in a de-energized state closing off the auxiliary section  34  of the circulation line. The energized relay closes the normally open second contact set CR 2 , activating the normal operation indicator light  26  to provide visual feedback of the feed prevention system&#39;s operational status to the operator who activated it, and opens the normally closed third contact set CR 3  so that the alarm condition indicator light is off. The energized relay opens the normally closed third and fourth contact sets CR 4 , CR 5  so that the auxiliary pump and heater are inactive. 
     Should the GFCI on the input circuit of the control relay  20  be triggered and accordingly disconnect the previous electrical connection between the 220V power supply and the spa pack, this same disconnection will cut off current flow in through the control side of relay. This switching of the relay from an energized to de-energized state to reflect the now non-operational state of the spa pack switches the open/closed state of each of the relay&#39;s contact sets. Accordingly, the first, third fourth and fifth contact sets CR 1 , CR 3 , CR 4 , CR 5  are returned to their normally closed states, thereby conductively linking the solenoid valve  24 , the alarm condition indicator light  28 , auxiliary pump  30  and auxiliary heater  32  with the 120V power supply. This energizes the valve to open the auxiliary sections  34  of the spa&#39;s circulation line, activates the auxiliary pump  30  to circulating water through the circulation line from and back to the tub via the auxiliary circulation section  34 , and activates the auxiliary heater to continue to heat the water to prevent freezing. The alarm condition indicator light  28  provides a visual indicator that the freeze prevention system has activated, so that an operator will realize the spa pack has cut out and may require resetting of the GFCI or some other repair or maintenance. 
     If the spa pack returns to proper functionality after resetting of the GFCI, then the closing of the relay&#39;s input control circuit by the GFCI re-establishment of electrical connection to the power supply, then the relay will once again energize, thereby closing the solenoid valve, re-illuminating the normal condition indicator light, and deactivating the alarm condition indicator light, the auxiliary pump and the auxiliary heater. The spa pack continues to function in a normal manner until either the GFCI is tripped again, or the spa pack and freeze prevention system are shut down at the end of the freeze-risk season(s). On the other hand, if the spa pack fails to restart or run continuously upon resetting of the GFCI, the auxiliary motor and pump and alarm indicator will continue to operate or again initialize to prevent the water in the spa from freezing and inform any present party of the spa pack&#39;s failure. If the spa pack is unable to function properly, the owner of the spa may shut down the freeze prevention system, drain the water from the spa system and arrange for repair of problem or wait until the expiry of the cold weather season(s) to further address the problem. For safety reasons, the output or controlled circuit of the relay is preferably protected by another GFCI, in which case freezing is still possible should both GFCIs be tripped, but the risk of spa damage due to freezing is still significantly reduced by the addition of the freeze prevention system as an emergency backup to the spa pack. 
     The auxiliary heater is preferably a space heater disposed within the tub enclosure of the spa so as to warm the space inside this enclosure. Heat thereby transfers to the circulation pipes within this space, and thus to the water being pumped therethrough by the auxiliary pump, and also transfers to the tub itself and the volume of water therein. However, other embodiments may employ other arrangements, like an inline auxiliary water heater installed on the circulation line for feeding of water therethrough under operation of the auxiliary pipe or use of heat tape on circulation piping, provided the amount of water heating is sufficient together with the circulation to prevent freezing. Minimum heating and circulation requirements may vary depending on variations in climate conditions (temperature) and size of tub (volume of water). It may also be possible to attain sufficient performance through use of circulation without heat, or heat without circulation. 
     In the illustrated embodiments the spa pack and the freeze prevention components are powered by power supplies of different voltages, but other embodiments are also possible. For example, some spa packs will run off a 120V power supply, and It may also be possible to turn the freeze prevention components off a 220V power supply in 220V spa pack embodiments. In either of these alternate cases, the same voltage of power supply could be used on both relay circuits. It may be possible to wire both circuits of the relay off a single power supply by wiring the controlled output side of the relay to the spa power supply before and parallel to the GFCI protecting the spa pack. However, the freeze prevention system of the illustrated embodiments that runs off lower voltage than the spa pack is intended to provide enough heating and circulation of the water to prevent freezing, but not to provide sufficient levels for actual use of the spa. Accordingly, the freeze prevention system requires less power, as it is not intended to heat the water to the much higher temperatures achievable by the spa pack to prepare the tub for occupants. 
     The freeze protection system may be functional without the use of the valve to open and close a pathway to the auxiliary pump depending on the status of the spa pack and the freeze prevention system. On the other hand, a second valve may be added at the opposing outlet side  14   b  of the auxiliary circulation section to more fully close off this section when the spa pack is functioning properly. Further separation of the parallel sections of the overall circulation pipework may be provided by an additional one or two valves that open and close in opposition to that illustrated in the Figures, thereby closing off the pathway to the pump of the spa pack when the freeze prevention components activate. While the described embodiments include indicator lights to reflect that the relay is operational to sense the spa pack operational status and reflect when the spa pack has ceased operation, it will be appreciated that the number and type of indicators may change. For example, an audible alarm could replace the alarm condition light indicative of the spa packs shut down and the freeze protection activation. While indicators could be removed altogether, it is preferable that some feedback on the status of the system be provided for easy recognition by the spa owner/operator. 
     Components of the freeze protection system of the present invention may be sold as an add-on kit for wiring and or plumbing to existing spa packs, or may be incorporated into spa pack designs themselves. It will be appreciated that the present invention is compatible with spa pack designs of various configurations, including those which incorporate the GFCI as a built-in or included component and those which include more than a single pump. The relay-based illustrated embodiments provides a simple solution for detecting de-activation of the spa pack, but will be appreciated that other sensor arrangements may alternatively be employed to monitor conditions reflective of an operational status of the spa pack, and trigger activation of one or more freeze prevention components in response to de-activation of the spa pack. Furthermore, the conditions being monitored need not necessarily relate to characteristics of the electrical connection between the spa pack and its power supply. As an example, one or more sensors could instead monitor such conditions as water temperature in the spa to check whether the spa pack is operating properly. 
       FIG. 3  shows a second embodiment similar to the first embodiment, but adding a single pole switch  40  on the 120V line, adding fuses on either side of the control rely 20, and featuring two additional heater devices  44 ,  46  wired respectively to two additional relay contact sets CR 6 , CR 7 , which are normally open so as to close when the control relay  20  is energized. The switch  40  acts as an off/on summer/winter switch to allow selective disconnection of the relay-controlled components from the 120V power supply when freeze prevention protection is not required. The additional heater devices  44 ,  46  are provided to deal with a situation which potentially arises where the solenoid  24  and auxiliary pump  30  become activated, then de-activated, leaving water behind in the by-pass line defined by the auxiliary pump and pipe. For example, this may occur where the spa pack GFCI is tripped, causing the freeze prevention system to kick in, but someone is on hand to reset the GFCI and finds that the spa thereafter reinitializes and runs without re-tripping. 
     In such a situation, the potential would exist for the water in this bypass line to freeze when the hot tub is in normal operation. Having said that, when the tub is in normal operation, and the control relay  20  thus being energized, the to additional relay contact sets CR 6 , CR 7  will close, thus energizing the additional heating devices  44 ,  46 , which may be provided in the form of a respective short length of self-regulating heat tape on the emergency auxiliary circulating pump  30  and on the solenoid  24 . By energizing these additional heating devices during normal operation of the spa, there is self-regulating heat to keep the water left in the bypass lines from freezing during these normal operating conditions of the spa. As mentioned above, it may be possible to replace the emergency auxiliary heater  32 , which comes on at loss of energy to the control relay  20 , with a lower energy consuming heat tape instead of a space heater. This self-regulating heat tape could be taped onto the normal operating pump and possibly the supply and suction lines of the circulating pump. 
     Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without department from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.