Apparatus for monitoring operation of heating and cooling systems

Apparatus is provided for monitoring operation of a heating and/or cooling system. The apparatus includes a programmed first processor for processing data relating to selected system operating conditions and for transmitting coded data signals indicative thereof, and a portable display module having an electrical conduit for electrically connecting the module to the first processor to provide one-way electrical communication therebetween. The module further includes a programmed second processor for processing the data signals transmitted by the first processor and a display device which is controlled by the second processor to provide a human readable indication of selected system operating conditions, including the current mode of operation of the system and any detected failure conditions. The first processor includes a memory for storing past system failure conditions. The apparatus includes a memory operable switch for inputting a signal to the first processor. In response to the input signal, the first processor transmits a coded data signal indicative of the last known system failure condition, even if such failure con&ion is no longer present.

FIELD OF INVENTION 
This invention relates generally to monitoring apparatus and in particular 
to improved apparatus for monitoring operation of heating and cooling 
systems. 
BACKGROUND ART 
Monitoring heating and cooling systems for potential and/or actual 
malfunctions is a significant aspect of maintenance and repair of such 
systems. Undesirable consequences may result if such malfunctions or 
potential malfunctions remain undetected and unrepaired. 
According to prior practice, various types of malfunction indicators have 
been used, including alarms, buzzers, flashing and/or static lights, etc. 
However, such malfunction indicators typically do not indicate a specific 
malfunction or problem. It is also known in the art to provide continuous 
monitoring of heating and cooling systems and to send a signal indicative 
of system malfunction via telephone modem or the like. Such continuous 
monitoring apparatus, while having the advantage of identifying specific 
malfunctions, usually require dedicated telephone lines and expensive 
monitoring equipment. 
There is therefore a need for improved apparatus for monitoring operation 
of heating and cooling systems, which is relatively inexpensive and yet 
which identifies specific system operating conditions and malfunctions. 
SUMMARY OF INVENTION 
In accordance with the present invention, apparatus is provided for 
monitoring operation of a heating and/or cooling system. The apparatus 
includes first processing means for processing data relating to operation 
of the system in accordance with a first set of program instructions and 
for transmitting coded data signals indicative of selected system 
operating conditions, and a portable display module having connecting 
means for electrically connecting the module to the system, whereby the 
data signals are transmitted to the display module. The display module 
further includes second processing means for processing the data signals 
in accordance with a second set of program instructions and for providing 
a human detectable output indicating selected system operating conditions. 
In accordance with one feature of the invention, the apparatus is a passive 
monitoring apparatus, which waits for the heating and/or cooling system 
being monitored to transmit the data signals. As such, the operation of 
the heating and/or cooling system is not interrupted. 
In accordance with another feature of the invention, the apparatus includes 
display means which is controlled by the second processing means to 
provide a human readable indication of selected system operating 
conditions. 
In accordance with still another feature of the invention, the apparatus 
includes user controllable input means for inputting a control signal to 
the first processing means. The first processing means is operative to 
transmit a data signal to the second processing means indicative of a last 
known system failure condition in response to the control signal. The 
second processing means in turn controls the display means to provide a 
human readable indication of the last known system failure condition. 
In the preferred embodiment, the apparatus is used to monitor operation of 
a heating system having automatic ignition control. The apparatus is 
connectible to the ignition control by means of an electrical conduit for 
receiving data signals transmitted by the first processing means, which is 
also programmed to effect automatic ignition control and is preferably 
resident on an ignition control printed circuit board in the heating 
system. 
The monitoring apparatus according to the present invention may be 
programmed to monitor operation of various types of heating systems, such 
as gas-fueled furnaces, gas-fired water heaters and combination water 
heating/space heating systems.

BEST MODE FOR CARRYING OUT THE INVENTION 
In the description which follows, like parts are marked throughout the 
specification and drawings with the same respective reference numbers. The 
drawings are not necessarily to scale and in some instances proportions 
may have been exaggerated in order to more dearly depict certain features 
of the invention. 
Referring to FIG. 1, apparatus for monitoring operation of a heating system 
(not shown) is depicted. The monitoring apparatus includes a portable 
display module 10 having an electrical conduit 12 for connecting module 10 
to an ignition control printed circuit board (not shown) of the heating 
system, and an ignition control processor 14, which is resident on the 
ignition control printed circuit board of the heating system. Processor 14 
is programmed to transmit coded data signals indicative of selected 
operating modes of the heating system, which will be described in greater 
detail hereinafter. For example purposes only, the operation of the 
monitoring apparatus will be described hereinbelow with reference to a 
combination space heating/water heating system. However, the monitoring 
apparatus of the present invention is not limited to monitoring operation 
of a combination space heating/water heating system, but may also be used 
to monitor operation of other types of heating and/or cooling systems, 
such as gas-fueled furnaces, stand-alone water heaters, air conditioning 
systems and combination heating/cooling systems, such as heat pumps and 
packaged heating/cooling units. 
Display module 10 includes a processor 16, a display device 18, which is 
preferably a liquid crystal display, and a battery power supply 20. When 
display module 10 is connected by means of conduit 12 to the heating 
system's ignition control printed circuit board, processor 16 is operative 
to process the data signals received from processor 14 in accordance with 
a predetermined set of program instructions and to control display device 
18 to display selected operating modes of the heating system in 
human-readable form, as will be described in greater detail hereinafter. 
Processor 14 and processor 16 are each preferably microcomputers of the 
ST62T25B6 type, manufactured and sold by SGS-Thomson Microelectronics. 
In accordance with one aspect of the invention, the communication protocol 
between processor 14 and processor 16 is one-way only, that is, data 
signals are transmitted from processor 14 to processor 16. Of course, the 
main function of processor 14 is to control the ignition sequence in the 
heating system. Since processor 16 is passive, it waits to receive data 
signals from processor 14. Accordingly, the ignition control operation of 
processor 14 is not in any way interrupted by processor 16. 
In accordance with another aspect of the invention, the monitoring 
apparatus includes a user-controllable input switch 22. In response to 
activation of switch 22, processor 14 transmits a data signal indicative 
of the most recently detected failure condition (i.e., the last failure 
state) of the system, even if the last failure state is no longer present. 
Processor 16 is programmed to decode the data signals transmitted by 
processor 14 and includes a memory for storing the decoded data. 
Referring also to FIGS. 2A-2G, operation of the monitoring apparatus 
according to the present invention will now be described in detail. FIG. 
2A depicts the Data Transmission Routine of processor 14. FIGS. 2B and 2C 
depict the Incoming Data Interrupt Routine of processor 16. Processor 16 
continually refreshes display device 18, while it waits for data signals 
from processor 14. 
When processor 14 is not transmitting data, it generates a binary coded 
"high" Data Ready signal. When the Data Ready signal goes "low", it 
indicates that processor 14 is ready to transmit data. Data is transmitted 
one bit at a time as a series of relatively short (e.g., 10 microseconds) 
pulses, with a longer interval (e.g., approximately 1 millisecond) between 
successive data pulses. The data is transmitted on a different 
transmission line from the Data Ready signal. The Data Ready signal is 
normally "high". Each time the Data Ready signal goes "low" it is an 
indication that a data bit is being transmitted. Processor 16 refreshes 
display device 18 between successive data pulses. 
As indicated in FIG. 2B, when the Data Ready signal goes "low", processor 
16 sets a 240 microsecond timer and increments a Data Ready Counter to 
begin counting the data bits. An eight-bit Data Buffer is loaded with the 
incoming data and as each data bit is transmitted by processor 14, the 
data already stored in the Data Buffer is left-shifted. 
As shown in FIG. 2A, data is transmitted by processor 14 in the following 
sequence: Tank Temperature, Temperature Setpoint, Operating State, 
Ignition Try Counter, Input Register Data and Failure Condition Data. When 
the Data Ready Counter indicates a first eight-bit count (Data Ready=8), 
the eight bits of data in the Data Buffer are stored in the Tank 
Temperature Buffer (TT.sub.-- Buf). The first eight bits of data indicate 
the temperature of the water stored in the tank of the combination water 
heating/space heating system. 
As indicated in FIG. 2C, when the Data Ready Counter indicates a second 
eight-bit count (Data Ready=16), the eight bits of data in the Data Buffer 
are stored in the Setpoint Buffer (SP.sub.-- Buf). The second eight bits 
of data indicate the desired temperature of the water stored in the tank. 
When the Data Ready Counter indicates a third eight-bit count (Data 
Ready=24), the eight bits of data in the Data Buffer are stored in the 
State Buffer (ST.sub.-- Buf). The third eight bits of data indicate the 
current operating mode or state of the system. When the Data Ready Counter 
indicates a fourth eight-bit count (Data Ready=32), the eight bits of data 
in the Data Buffer are stored in the Try Counter Buffer (TC.sub.-- Buf). 
The fourth eight bits of data indicate the number of tries or attempts to 
ignite a gas-air fuel mixture to heat the water stored in the tank. When 
the Data Ready Counter indicates a fifth eight-bit count (Data Ready=40), 
the eight bits of data in the Data Buffer are stored in the In Register 
Buffer (iR.sub.-- Buf). The fifth eight bits of data indicate selected 
system inputs to processor 14, such as, for example, a demand for space 
heating signal from a room thermostat. The sixth and last eight bits of 
data indicate any failure condition or other malfunction in the system so 
that the entire data stream consists of forty-eight bits (six bytes of 
eight bits each). After all forty-eight bits have been transmitted, the 
Data Ready signal will remain low for 240 microseconds or more. 
As indicated in FIG. 2B, when processor 16 detects that the Data Ready 
signal has remained low for 240 microseconds or more, it knows that a 
"Stop" bit has occurred, which means that the data transmission has 
ceased. If all forty-eight bits have been received, then the data is 
deemed to be valid and the data is transferred from the temporary storage 
buffers into permanent memory storage locations for access by processor 
16. As indicated in FIG. 2B, the last eight bits of data in the Data 
Buffer is stored in the Failure Flag (Failfig.) memory location. The Tank 
Temperature Buffer is stored in the Tank Temperature flank (Tank Temp.) 
memory location, the Setpoint Buffer is stored in the Setpoint memory 
location, the State Buffer is stored in the State memory location, the Try 
Counter Buffer is stored in the Try Counter (Tryctr) memory location, and 
the In Register Buffer is stored in the In Register (InReg.) memory 
location. If the data stream consists of less than forty-eight bits, the 
data is discarded and the Data Ready Counter is cleared. 
The Display Routine is depicted in FIG. 2D. If processor 16 does not 
receive valid data within thirty seconds it will execute Display Routine A 
for two seconds and then execute Display Routine B for two seconds. Until 
valid data is received, processor 16 will continue to alternately execute 
Display Routine A and Display Routine B. Display device 18 has the 
capability to display two lines of sixteen characters. 
Display Routine A is depicted in FIG. 2E. Processor 16 controls display 
device 18 to display the version of the software instructions for which 
processor 16 is programmed (Display Version Number) on the first line of 
display device 18 and the words "Patent Pending" (Display Patent Pending) 
on the second line of display device 18. Further, processor 16 will 
control display device 18 to indicate a low battery condition (Display Low 
Battery), if applicable. 
Display Routine B is depicted in FIG. 2F. Processor 16 controls display 
device 18 to display the word "HEATCRAFT" (Display HEATCRAFT) on the first 
line of display device 18 and the notice "Copyright 1993" (Display 
Copyright 1993) on the second line of display device 18. Further, a low 
battery condition, if applicable, is also displayed. 
Referring again to FIG. 2D, assuming valid data is received within thirty 
seconds, processor 16 determines whether the system being monitored is a 
combination water heating/space heating system. If the Tank Temperature 
data indicates that the tank temperature equals 255.degree. F. (OFF in 
hexadecimal code), then the system being monitored is not a combination 
water heating/space heating system. Further, if the Tank Temperature data 
indicates that the tank temperature is less than 16.degree. F. (less than 
10 in hexadecimal code), then the system being monitored is not a 
combination water heating/space heating system and the first line of 
display device 18 is not used. If, however, processor 16 determines that 
the tank temperature is between 16.degree. F. and 254.degree. F., then the 
system being monitored is assumed to be a combination water heating/space 
heating system and the Display First Line Routine (FIG. 2G) is executed. 
Referring to FIG. 2G, processor 16 controls display device 18 to indicate 
the tank temperature set point (Set Temp) and the actual water temperature 
flank Temp) on the first line of display device 18. 
The Display Second Line Routine is also depicted in FIG. 2G. The second 
line of display device 18 is used to display the current state or 
operating mode of the system. The data indicative of the current state of 
the system is transmitted by processor 14 in hexadecimal code. Processor 
16 uses a Look Up Table to decode the hexadecimal code transmitted by 
processor 14 and determine the actual operating state. The Look Up Table 
is indicated in the following Table I. 
TABLE I 
______________________________________ 
STATE HEX FAILFLG 
NAME VALUE (BINARY) DISPLAY 
______________________________________ 
ST.sub.-- WT 
01 WAIT 
ST.sub.-- PRG 
02 PURGE 
ST.sub.-- Y 
03 COOLING 
ST.sub.-- IGN 
04 IGN TRIAL#.sub.-- (TRYCTR) 
ST.sub.-- G 
05 MANUAL 
ST.sub.-- RL 
06 ROLLOUT OPEN 
ST.sub.-- PPR 
07 PRESS SWITCH OPEN 
08 IGN TRIAL#.sub.-- (TRYCTR) 
ST.sub.-- FLEST 
09 SUCCESSFUL IGNITION 
ST.sub.-- FS 
0A FLAME 
ST.sub.-- LM 
0B LIMIT OPEN 
ST.sub.-- FF 
0C IGNITION FAILURE 
ST.sub.-- WG 
0E XXXX XXX1 W'GUARD LIMIT 
0E XXXX 1XX0 BAD THERMISTOR 
0E XXXX 0X10 W'GUARD PRESSURE 
0E XXXX 0100 W'GUARD IGNITION 
ST.sub.-- DD 
0F CHANGE CONTROL 
ST.sub.-- DO 
11 DELAY OFF 
ST.sub.-- PF 
12 PRESS SW CLOSE 
ST.sub.-- FLSTB 
13 FLAME STABILIZATION 
ST.sub.-- PP 
14 POST PURGE 
ST.sub.-- BF 
15 BOARD FAILURE 
ST.sub.-- CB 
16 CONDENSATE BLOCK 
ST.sub.-- MIGN 
55 IGN TRIAL #.sub.-- (TRYCTR) 
LFS.sub.-- WLM 
70 W'GUARD LIMIT 
LFS.sub.-- WPS 
71 W'GUARD PSW 
LFS.sub.-- WFF 
72 W'GUARD IGNITION 
LFS.sub.-- PF 
73 PSW CLOSE 
FLS.sub.-- RL 
74 FLAME ROLLOUT 
LFS.sub.-- LM 
75 LIMIT OPEN 
LFS.sub.-- CC 
76 CHANGE CONTROL 
LFS.sub.-- BF 
77 BOARD FAILURE 
LFS.sub.-- PPR 
78 PRESS SW OPEN 
LFS.sub.-- NN 
80 NONE 
______________________________________ 
When processor 16 determines the operating state, it controls display 
device 18 to display the operating state in human-understandable form. For 
example, if processor 16 determines that the state is ST.sub.-- PPR, it 
will display "PRESS SWITCH OPEN" on display device 18, which indicates 
that a pressure switch for measuring the system's combustion air blower 
(not shown) discharge pressure is in an open position. 
Referring again to FIGS. 2A and 2D, activation of input switch 22 (FIG. 1) 
results in processor 14 transmitting a signal indicative of the last known 
failure condition ("Last Fail State") of the system, instead of the 
current operating state of the system. If processor 16 determines that the 
state is greater than a predetermined value (6F in hexadecimal code), it 
will display the last known failure condition on the first line of display 
device 18. As indicated in Table I, the hexadecimal code assigned to each 
of the Last Fail States (LFS) is greater than state 111 (6F in hexadecimal 
code). 
If the current state of the system indicates a failure condition or other 
malfunction, a Watchguard state (ST.sub.-- WG) is indicated. As shown in 
Table I, there are four possible failure conditions indicated by the 
Watchguard state. Typically, a combination water heating/space heating 
system will include a temperature limit switch, a thermistor for sensing 
water temperature and a pressure switch. In the event of failure of any of 
these three sensors, a Watchguard state is indicated. The particular 
failure condition is indicated by an eight-bit binary code stored in the 
Failure Flag (Failflg) location in memory. A fourth Watchguard condition 
is indicated by an ignition failure, which results when ignition fails to 
occur after a predetermined number of tries (e.g., 6 tries). The control 
of a combination water heating/space heating system, including the 
Watchguard Routine, is described in greater detail in co-pending U.S. Pat. 
application Ser. No. 08/296,112, entitled "Combination Water Heating And 
Space Heating Apparatus", filed Aug. 25, 1994, now U.S. Pat. No. 
5,544,645, the specification of which is incorporated by reference herein. 
In accordance with the present invention, apparatus is provided for 
monitoring operation of a heating and/or cooling system. The monitoring 
apparatus is programmed to display the current operating mode of the 
system, including any failure condition or other malfunction. The 
apparatus provides passive monitoring and does not interrupt the main 
system control function, but rather waits for the system control to 
transmit data indicative of system operating modes. The apparatus is 
programmable for monitoring various types of heating and/or cooling 
systems and is particularly well-suited for use by a service technician to 
detect and diagnose system malfunctions and potential malfunctions. 
Various embodiments of the invention have now been described in detail, 
including the best mode for carrying out the invention. Since changes in 
and modifications to the above-described embodiments may be made without 
departing from the nature, spirit and scope of the invention, the 
invention is not to be limited to said details, but only by the appended 
claims and their equivalents.