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Guys, check your thermostat temp accuracy.

S

steppinthrax

Diamond Member
So last month we had a $422 electric bill. It was high for many reasons, but one thing we noticed was our heat pump kept running all day during the coldest days. I read somewhere that a heat pump may run continuously during deep winter, simply because it's having a hard time pulling the heat from outside.

One day I was playing around with a new infrared thermometer from harbor freight (point and shoot) and when I pointed it to the wall where the thermostat was on it was reading 70 degrees, but the thermostat was reading 67. I changed the batteries (same thing). I bought a brand new thermostat and installed it (Honeywell Wifi). The new thermostat indicated the room was 71 degrees. I placed my old thermostat on top of the new one. The old thermostat would in many cases show several degrees lower then the new thermostat. The reading was also inconsistent.
 
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Hmm interesting, I bet no one ever thinks about the temperature sensor being off. This will be a good argument to convince my wife to let me get one of those wifi-controlled thermostats 😀
 
Kaido said:
Hmm interesting, I bet no one ever thinks about the temperature sensor being off. This will be a good argument to convince my wife to let me get one of those wifi-controlled thermostats 😀
Click to expand...

I bought the Honeywell RTH6590WF. It looks exactly like the Honeywell basic thermostats but is connects to your home Wifi and uses a android App. It wasn't very much (99.00). You can monitor the temp and login to shut it off from anywhere. The next model up from that has a touch screen and displays weather and other stuff. Looks like a smart phone.
 
To get 70F in our house, as measured with a decent Hg thermometer, we need to set the thermostat at 76F. The thermostat is okay, just placed poorly.
 
shortylickens said:
On the middle floor its very accurate.

Problem with a townhouse is all the heat shoots upstairs. No way to control it.
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😕

Lower-floor vents should be open during the winter. Upstairs vents should be closed.

We manage to keep our townhouse relatively consistent with just a bit of forethought.
 
We do push the hot air downstairs with the vents and dampers. It still shoots upstairs.
Because heat rises.

And we cannot control it. Everything is wide open.
 
😕
Does the numerical number matter? Shouldn't you be setting the temperature for what feels comfortable? "The thermostat says it's 70 degrees. Therefore I am comfortable?"

(And me... I'm uncomfortable. Too hot in here, must be 85 or so. I'll turn the control down on my way to bed, regardless of what temperature it says.)
 
My thermostat is off by about 1 degree from the sensor that I put in it which is actually what is determining the room temp. (thermostat is just there for show and to have something to put sensor in. 😛)

With only two devices to compare though, not really sure which one is truly off. 😛 The sensor is a DS18B20 and is known to be fairly accurate though, while the thermostat just uses a thermistor. Non electronic thermostats that simply use metal contraction can probably get off over time too as the metal changes over time. At least that's my guess.

I tend to just go by what I'm comfortable at though. If it's consistently off then it should not be too big of a deal if it's only 1-2 degrees. More than that I'd probably replace it just because I'd be annoyed that the temp I see is not the right one.
 
I wouldn't be surprised if a thermometer was off by ~2 Celsius. I have three consumer grade thermometers all off by 2 or 3 degrees -- also have an infrared camera, but I only trust that to +/-5 C (~20 F?) because it needs a bunch of variables to be set up properly to read accurately and I just use common averages.
 
I'm currently staying with my dad and the apartment he's staying in does not retain heat. Its awful. The thermostat is always showing 70-71 degrees. When the heat comes on its great, but when it shuts off it gets cold very quickly.
 
DrPizza said:
😕
Does the numerical number matter? Shouldn't you be setting the temperature for what feels comfortable? "The thermostat says it's 70 degrees. Therefore I am comfortable?"

(And me... I'm uncomfortable. Too hot in here, must be 85 or so. I'll turn the control down on my way to bed, regardless of what temperature it says.)
Click to expand...

This was exactly my initial reaction. That's crazy. Who sets the temperature at a number, without regard for comfort? It's either too cold, too hot, or you have to wear too much clothing or too little.

OP, are you going to us that you still set the new thermostat at 67, except that now the house is three degrees cooler than before? Or are you now setting the thermostat at 70?
 
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I loathe the heat pump we have in our apartment. In general the heating system is just awful. Every room is a different temperature (by a few degrees) and it's never really warm in deep winter unless it's absolutely cranked.
 
steppinthrax said:
I bought the Honeywell RTH6590WF. It looks exactly like the Honeywell basic thermostats but is connects to your home Wifi and uses a android App. It wasn't very much (99.00). You can monitor the temp and login to shut it off from anywhere. The next model up from that has a touch screen and displays weather and other stuff. Looks like a smart phone.
Click to expand...

I saw a thing in a magazine last week about a Honeywell Wifi thermostat which was pretty appealing. I was never jazzed about the concept of the Nest because it tries to anticipate (i.e. "learn") your routine and we don't have a routine.

But the Honeywell apparently has an app for your smartphone that lets you tell the thermostat to lower the temp once you've gone a user-defined distance from your home, and raise it back when you've returned inside the threshold. That idea is appealing since it's so automatic.
 
NetWareHead said:
If you place the Hg thermometer next to the thermostat, do both readings match?
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Yeah, if I hold the thermometer pressed against the wall next to the thermostat, it reads the same. The wall where the thermostat is mounted is too close to the furnace closet.
 
OP what is your backup heat source if you have one? Electricity is very expensive now and NG is very cheap. I have turned up the balance point as high as I can on my HP to whenever possible heat with NG. Even if your backup heat source is electric resistance you may find it cheaper to heat with that than trying to extract heat out of frigid air while running fans and compressors.

The problem of course is the variances in the weather from billing cycle to billing cycle. Makes it difficult to determine what's best.
 
kranky said:
I saw a thing in a magazine last week about a Honeywell Wifi thermostat which was pretty appealing. I was never jazzed about the concept of the Nest because it tries to anticipate (i.e. "learn") your routine and we don't have a routine.

But the Honeywell apparently has an app for your smartphone that lets you tell the thermostat to lower the temp once you've gone a user-defined distance from your home, and raise it back when you've returned inside the threshold. That idea is appealing since it's so automatic.
Click to expand...
I could be wrong, but I think you could do the exact same thing with Nest and Tasker.
 
Carson Dyle said:
This was exactly my initial reaction. That's crazy. Who sets the temperature at a number, without regard for comfort? It's either too cold, too hot, or you have to wear too much clothing or too little.

OP, are you going to us that you still set the new thermostat at 67, except that now the house is three degrees cooler than before? Or are you now setting the thermostat at 70?
Click to expand...
If I let my SO set the temperature for (her) comfort, it'd be set at about 79F right now.
 
Heat pumps suck for heating. Even the heat pump in my basement has an electric 'booster' and I'm in Atlanta. I found better performance, though, using an oil-filled electric radiator. Electricity in my area (coop) is cheap in the Winter months so it is a win-win and I don't have to hear the heat pump run when I set its thermostat to 58ºF.
 
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