Background:
In 2001 I built a fairly large home. Heating and cooling are provided by five heat pumps. In 18 years I have experienced heat pump failure from time to time. The most common problem – about a half dozen times – has been a gradual loss of efficiency caused by a slow leak of refrigerant. Another creeping performance decline has been caused by my occasional failure to clean filters when needed.
Problem:
Gradual heat pump performance degradation often goes unnoticed until long after the problem begins. Meanwhile, the additional cost of relatively inefficient heating/cooling rises until the issue is addressed. In my case, the extra cost of pumping more well water for heat pump thermal assist adds to the financial burden.
Need:
I need an inexpensive and simple way for my smart home to keep an eye on my heat pumps, informing me when their performance is subpar. While it would be nice to determine absolute performance such as BTU per hour, that’s not essential. I just need to know whether something needs to be fixed.
Constraints:
I’m no HVAC expert, but the service people have told me the easiest way to confirm efficient heat pump operation is to compare ambient room temperature to the temperature of air coming out of the registers when the heat pump is running. They say that the differential should be around 15 to 20 degrees F. under normal conditions.
Therefore, one cannot infer heat pump performance by simple measurement of plenum temperature; a properly functioning heat pump might provide 80 degree air at the register if ambient temperature is 100 degrees, but 60 degree air if ambient is 80 degrees.
Likewise, one cannot make inferences based on heat pump percent run time. The air conditioning will always run a greater portion of the time on a hot day.
Hardware:
My approach is to measure plenum air temperature by placing a sensor at a register. Not wanting to get bogged down with Arduino/ESPxxx/MQTT/1-wire temperature sensing solutions (especially since this is still in the experimental stage), I bought an HS-FS100+ Z-Wave Flex Sensor (without the cable options). I run it on USB power rather than batteries so I can get register temperature measurements at 60 second intervals.
HS3 Interface:
I have created events to perform the following actions: Once a minute I compare the current plenum (register) temperature with the one I read a minute ago. I then compare this temperature increment with the maximum difference I have read today and update the day’s maximum difference if necessary.
At the end of each day, I compare my day’s maximum 60-second temperature increment against a standard constant I have previously determined by experiment. If the comparison is unfavorable, I send myself an email addressing the problem. It’s also easy to store each day’s maximum in a virtual device, which the Device History plug-in can use to create performance charts.
Call for Comments:
There may be a better way to monitor HVAC heat pump performance. If anyone can offer an improved solution, please advise.
In 2001 I built a fairly large home. Heating and cooling are provided by five heat pumps. In 18 years I have experienced heat pump failure from time to time. The most common problem – about a half dozen times – has been a gradual loss of efficiency caused by a slow leak of refrigerant. Another creeping performance decline has been caused by my occasional failure to clean filters when needed.
Problem:
Gradual heat pump performance degradation often goes unnoticed until long after the problem begins. Meanwhile, the additional cost of relatively inefficient heating/cooling rises until the issue is addressed. In my case, the extra cost of pumping more well water for heat pump thermal assist adds to the financial burden.
Need:
I need an inexpensive and simple way for my smart home to keep an eye on my heat pumps, informing me when their performance is subpar. While it would be nice to determine absolute performance such as BTU per hour, that’s not essential. I just need to know whether something needs to be fixed.
Constraints:
I’m no HVAC expert, but the service people have told me the easiest way to confirm efficient heat pump operation is to compare ambient room temperature to the temperature of air coming out of the registers when the heat pump is running. They say that the differential should be around 15 to 20 degrees F. under normal conditions.
Therefore, one cannot infer heat pump performance by simple measurement of plenum temperature; a properly functioning heat pump might provide 80 degree air at the register if ambient temperature is 100 degrees, but 60 degree air if ambient is 80 degrees.
Likewise, one cannot make inferences based on heat pump percent run time. The air conditioning will always run a greater portion of the time on a hot day.
Hardware:
My approach is to measure plenum air temperature by placing a sensor at a register. Not wanting to get bogged down with Arduino/ESPxxx/MQTT/1-wire temperature sensing solutions (especially since this is still in the experimental stage), I bought an HS-FS100+ Z-Wave Flex Sensor (without the cable options). I run it on USB power rather than batteries so I can get register temperature measurements at 60 second intervals.
HS3 Interface:
I have created events to perform the following actions: Once a minute I compare the current plenum (register) temperature with the one I read a minute ago. I then compare this temperature increment with the maximum difference I have read today and update the day’s maximum difference if necessary.
At the end of each day, I compare my day’s maximum 60-second temperature increment against a standard constant I have previously determined by experiment. If the comparison is unfavorable, I send myself an email addressing the problem. It’s also easy to store each day’s maximum in a virtual device, which the Device History plug-in can use to create performance charts.
Call for Comments:
There may be a better way to monitor HVAC heat pump performance. If anyone can offer an improved solution, please advise.
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