Temp Variation with Heat Pump White Rogers 1F95-1277 t stat
First off I have looked at this site the past few days and am amazed at all the helpful people out there. I hope I am able to pick a few brains without annoying the heck out of anyone.
I am using a heat pump for the first time as I have moved into a different house. I have a few questions since this is all new to me.
1. My t stat is set on 68-69 and comfortable for us. However, I have noticed that my system turns on and off quite a bit. It will run for about 10 min and then off for 8-10 min. The reading on the t stat never changes. My last electric bill was considerably higher than I would have anticipated and wonder if it is do to the constant on and off. Is there a way that I can manipulate my t stat for cycle times? I have read so much about these things that I have myself confused and need some professional direction. My HVAC guy said that my t stat only has a 1/2 degree +/- variance before it tells the unit to kick on. Is there a way to change this?
My heat pump is a Armstrong 4SHP14LE160P-1
The coil is a EC1P62DG-1
Aux Heat is a G1D93BU112D20D-2
I have approx 3600 sq ft that is being supplied by this unit. Specifically an unfinished basement with a couple of vents that are open and my main floor
Any advice or suggestions will be greatly appreciated.
The manual tells how to slow the cycle rate. Menu options 7 & 8 change to slow. Probably not going to be a noticeable difference in the electric bill though.
When you say your electric is considerably higher than you expected, it's hard to tell what that means. You're heating a 3600 sf house, in a fairly cold climate. It ain't gonna be cheap, even with a heat pump.
I would have the system checked out by a QUALIFIED service co.
If the system is maintaining temp, and cycling on/off, at least you know it's in the ballpark. Could be a sizing issue, or a minor adjustment that is needed.
"Hey Lama, hey, how about a little something, you know, for the effort." And he says, "there won't be any money, but when you die, on your deathbed, you will receive total consciousness." So I got that goin' for me, which is nice. - Carl Spackler
I have a 1F95-1291 which is the same but with humidity control. It is currently not in service because I wanted a wireless outdoor sensor, but it's a good stat.
Change the Cycle Rates, Cr Heat and Cr Cool to SL (slow). The defaults are both FA (fast).
FA uses a differential of 0.6F for heat and 1.2 for cool.
SL uses a differential of 1.2F for heat and 1.7 for cool.
SL should give you longer cycles.
Sounds like your HVAC guy is clueless.
I switched the cycle times per Garya505 to SL.
With the different variations in temp should I see that on my t stat. When I put the hold temp to 68 the unit will come on and run through cycles and shut off with out ever changing the 68 temp reading on the center of my t stat. My t stat never shows it going up 1.2 deg to 69 before it shuts off. The temp reading on the t stat never drops below 68 before it turns itself back on. Basically it always says 68. This doesn't seem right to me.
Thanks for the thoughts.
Ya, me too. I noticed the same thing with the temperature display, though it did seem that the cycles were longer.
Originally Posted by Nayr
well now I am confused even more LOL!!!
So do other t stats do the same thing? Meaning do they not register actual temps as they are in the room. Really seems weird that I don't see the variations on the t stat face.
My Prestige does that too, but it doesn't use a differential and may in fact hold temp within +/- 0.5F. I don't know but it never changes.
Originally Posted by Nayr
Many of the higher-end stats "lie" on the screen. Both Honeywell and White-Rodgers stats will show a temperature which is closest to the setpoint. That said, what is displayed on the screen is NOT what the stat is seeing/registering. I believe the Honeywell stats read temperature in 1/16ths of a degree.
So, the stat display may not change, but what it's telling you isn't what it is using to make its decisions.
Its because of both a rounding to factor. And a to stop complaints factor.
Originally Posted by Nayr
If it registered actual temp. It would need to read in tenths or even 100's of a degree. Most people would be annoyed by that.
Next annoyance without reading in 10ths or 100ths of a degree would be the temp read out flicker you would see if it didn't round. Your stat would be flickering between 67 and 68 quiet a lot if its didn't use a round to factor.
For testing, I just put a digital thermometer that reads in 10ths on the desk nearby.
You probably already know this, but with a heat pump it's good to have it maintain a very steady temp instead of having the temp rise and fall by a degree or two. This is doubly true if you have a 2-stage heat pump.
A flame-based furnace, even a 2-stage unit, creates HOT air at your ducts. it almost doesn't matter what temp the air from the returns is - the air at the ducts will be HOT. The system depends on mixing that hot air coming from the ducts with ambient temp air in the room, and typically raises the temp of a room fairly quickly. Which is good, because every second it runs costs quite a bit (except nat gas). But since it takes a minute or so to get up to temp and become efficient you want it to run for a reasonable period of time at the high-efficiency level, even if it means overheating the room a bit.
A heat pump works by sucking in air from the returns, warming it a bit and discharging it back into the room. Turnover of the air through the system is what keeps the room warm, instead of pumping hot air out a duct and hoping it mixes with the colder air in the room the way a furnace-based system does. But a heatpump's efficiency means it can do this all day long at a cost that is lower cost (in most areas of the country, and until it gets below a specific temp) than propane or fuel oil. So you can maintain a very, very consistent temp, with fewer hot and cold spots in the room.
What heat pumps are NOT good at is raising the temperature in a room. The air-turnover design means that rarely is the temp at the ducts more than 20 degrees higher than the air going in the returns - and this falls off even more as the outside temp goes down. So to raise the temp in a room by 2 degrees may take 2 hours on a cold night - which would mean kicking in the resistive coil aux heat - at double to triple the cost per BTU produced.
So the thermostat does everything it can to keep swings to a minimum - even if that means cycling the heat pump on and off at 10 minute intervals. There is a bit of lost efficiency with each cycle, but modern air handlers are set up to keep running a few seconds after the compressor shuts off to extract every last bit of heat from the tubing. And if you have a 2-speed compressor, it can run constantly at stage one power instead of cycling on and off at full power - which actually uses less electricity.
One of the other things you have to get used to (and there are caveats and exceptions to the norm) is that set-back thermostats can actually be counter-productive with a heat pump system. If you let the heat pump "take a rest" overnight by setting the overnight temp to 65, and then want it to be 69 degrees in the morning, it may end up having to resort to using the aux heat for 1/2 an hour to increase the temp by those 4 degrees. But if you leave it at 69 degrees all night long, the heat pump, especially a 2-stage, may be able to operate in high efficiency mode all night long keeping the temp constant - and using less electricity overall.
It's a science and the number of variables is nearly infinite, but if you watch how well your system does in colder weather (30 degrees and below) compared to warmer weather (30 to 50 degrees) you may be able to find some rules for minimizing your use of aux heat while keeping your house at the temp that feels most comfortable to you.