My house has central heat and air conditioning via an electric furnace and a heat pump.
On hot days, my hubby thinks the air conditioning works nonstop for 6 hours straight, and that it’s somehow a bad thing. I think it cycles on and off, but it’s quiet enough that it’s hard to be sure without going downstairs to listen every 15 minutes.
Is there a gadget I could make that would allow me to gather logs of when the heating or cooling is working and when it’s idle?
The thermostat is a Wi-Fi-enabled Honeywell unit but I don’t think there’s any way to get the information from there.
I was thinking I could mount a temperature probe in an air vent, or some sort of vibration sensor on the blower. But how would I connect this to a PC or to a (1st-gen) Raspberry Pi?
If your t-stat is wifi enabled, I assume there’s an app for it. With Nest, it’ll tell you exactly how long the heat or ac ran for and IIRC, a graphical representation of the times in cycled on and off throughout the day.
If you want to hobble something together, you could get a an hour meter and install it on the compressor.
It would actually be easier to install it on the furnace (I’d go across the blower motor connections), but one of my thoughts is that the compressor isn’t running all the time, but the furnace blower is. Either because it’s set to ON instead of AUTO, or because your t-stat is set to cycle it on and off randomly throughout the day day.
In either case, if you use an hour meter, it would be very easy to check it every 24 hours and see how long it’s run for during that time period. 6 or 7 hours is probably normal, 24 hours would be an issue and you’re electric bill would be huge.
While we’re at it, make sure the compressor (the outdoor part) isn’t full of leaves or grass clipping or has a bush or tree growing against it. If the coils are at all dirty, rinse them off with a hose. If they’re clogged, the AC will take a lot longer to cool down the house.
PS, those hour meters are really cheap and very easy to install as long as you’re comfortable doing some wiring. I put one on my air compressor so I’d have some idea as to how long it’s run since the last time I changed the oil. It took about a half hour and most of that time was spent mounting the timer in a box that I could mount on the compressor.
If the system itself won’t tell you when it is running, you can get a reasonable estimate of runtime with a wifi enabled indoor thermometer. I have a home weather station that reports indoor temp and humidity.
If you look at the daily temperature reading for the house on a graph, the peaks and valleys make it pretty obvious as to when the system was running and for how long.
Looks like mine ran about 4h:24m in the past 24 hours. Based on how I have the temperature profile set, it pretty much didn’t turn on for about a 12 hour period today.
Yes. A gadget like thisis what is specifically meant for an application like this.
Your husband is presumably not concerned about the duty cycle - the percentage of each day the equipment is operating - but the energy consumed by the equipment. Duty cycle is only relevant if the cooling load on the hottest day of the year is so large that the equipment can’t keep the place cool enough even running flat out.
You would install the energy meter ideally in the disconnect box right in front of the outside AC compressor. Obviously the 2 clamps go around the supply wires to the compressor.
The part he’s concerned over is the duty cycle, actually. Both in terms of the heat pump being insufficient for cooling the house on hot days, and of the risk of the condenser turning into a huge block of ice if the thing runs continuously for hours.
Thanks to all who replied. I think I’ll just use a temperature sensor, per txtumbleweed’s suggestion, as it’s cheap and it will also allow me to infer the heating cycles in winter.
Did you read the specs for this? Win7 / WinXP USB2.0? Really old technology. Make sure your computer can support it.
ETA: not concerned about the USB part too much.
The evaporator is what might freeze up, but if it does, it’s not due to duty cycle.
A heat pump should be able to run continuously without freezing up. If it tends to freeze up, your airflow is insufficient, due to poor design or clogged filters.
They say “USB 2.0/1.1/1.0”, which is a nice way of saying 1.0 ! Wired mice still use 1.0 too, it’s good enough if you don’t need high bandwidth.
I actually ordered the item from AliExpress, where the description mentions… Windows NT :).
Driver-wise, Windows 7 and 10 are pretty much the same… assuming they support 64-bit Windows 7. At worst I can connect it to a 32-bit Windows 7 virtual box or that old XP netbook I have in the basement. (XP is still all right to use IF it’s not connected to the Internet at all.)
The gadget in question works fine with Windows 10. The software that comes with it (on a mini-CD) is not pretty but it works. It shows a crude graph, but most importantly it can log everything to a CSV file.
There’s a temperature sensor inside the dongle itself, in addition to the probe. So, by dropping the probe into the forced-air outlet near my desk, I can plot the temperature of the air coming from the furnace/AC against the room temperature. I can even tell the difference between the times when the heat pump is heating (~33 °C) and the times when the 15 kW element is heating (~50 °C), so I have everything I need.