Do I need a special thermostat for my heat pump??
#11
I had a Trane XR14 air handler / heat pump combo installed a couple of years ago. It came with a heat strips for emergency backup heat. The stock thermostat that was installed is a non-programable Honeywell and works fine. The problem is the wife likes it to be a few degrees cooler while sleeping so we turn it a down a tad before going to bed and then back up in the morning. I’m getting tired of raising and lowering the temperature every day. I’d like it to come on before I get out of bed. No problem, just install a programmable one right? Just a few wires. I’m fairly handy, worked in the electronics industry for years and also wired several additions to our homes through the years so it should be a breeze. Well, not so fast. In the past few weeks I’ve tried three different programmable thermostats (1- White-Rogers & 2- Honeywell). All three were supposed to work with heat pump systems but none worked exactly right. In the heat mode, every single one of them also kicked on the emergency heat strips. Every single time. Even when the temperature difference called for was only 2 degrees. After the third one I decided that I must have it wired wrong so I called my HVAC guy. He came out, went through the wiring and the thermostat programming, scratched his head and said everything looked right but didn’t know why it was doing that. All three must be incompatible with my system. He could install one that programmable and it will definitely work with our system but they are “professional models”, not sold to the general public and it would cost $175 plus installation. (Suddenly manually changing the temps didn’t look that bad!) I passed and put the old stat back on.
I can’t imagine why Trane air handler/heat pump/ with electric em. heat combos are so different that they would require a special thermostat. Anyone have any HVAC experience on this?  What am I missing here?
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#12
Wire it so the heat strips only come on when manually switched on. The directions with the test at will have this option.
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#13
The standard operation for backup heat strips is 1.5 degrees, so if you are raising the temp 2 degrees, the strips are going to operate. Heat pumps are meant to be set and left alone during the colder spells, not lowered and raised- this causes the strips to operate since the heat pump won't raise the temp fast enough or at all during colder times. Disable this function and you may find the home cooling down and going into defrost more often, at which time, without strips, will cool the house quickly, use more energy raising the costs of running it and put more strain on the compressor.  You could try adding a time delay relay to the strips, but again, your defeating the designed purpose.

I'd say 80% of people who get a setback thermostat begin using the "Hold temp" setting sooner or later- - but trying it may work for you. There is a fine line between comfort and temp/humidity. Some thermostats read humidity and compensate, but I haven't found one yet that reads activity vs humidity vs temp vs respiration.
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#14
Thanks for the replies. I get conflicting answers on exactly when the heat strips should come on. Some folks say that they should come and assist the heat pump when the temperature increase called for is X or above. Other sites say that they are for emergency use only and should never come on unless you manually activate them at the thermostat.

Since electrical resistive heat is so much more expensive than running the heat pump, I'm surprised that it would so frequently be called on with only a two or three degree increase. I know the existing (non-programmable) never called for it, even when the temperature difference was 10 degrees or more.
Telling a man he has too many tools,
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#15
(03-26-2018, 11:25 AM)Terry W Wrote: Other sites say that they are for emergency use only and should never come on unless you manually activate them at the thermostat.

I would say that is absolutely wrong, at least it hasn't been that way on either of the 2 systems I had.
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.
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#16
You do know the heat pump transfers the heat outdoors to the inside of the home? The colder it gets outside, the less heat to transfer until you reach the balance point where the heat pump will run continuously just to maintain the temperature inside. Then it goes into defrost where it switches over to cooling mode. No strips at this point and your getting a cold house.
Not know your home or it's load calculation or your outdoor temps and humidity, I can't suggest anything but to let the system run as originally designed.
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#17
Had a Trane that I recently replaced with a Lennox.

The Trane heat pump was on top of an electric backup.  We replaced the thermostat several years ago with a new White-Rogers programmable thermostat.  Seemed like any normal thermostat.  Worked OK.

Our new Lennox has a Honeywell T6 Pro.  I watched the tech installing it with the new Heat Pump/Propane aux furnace system.  There's a series of setup screens to set the programming for this thermostat.  If I recall correctly, we had to step through about 22-25 questions, establishing settings about the system and preferences for temperature differentials and the like.  I think it was programmable for several different types of auxiliary heat setups.

You might look through the Honeywell website; quick review showed that their site describes what the various models will handle.
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#18
Thanks all. Quick follow up question. If and/or when the electric strips come on as a heat assist or in defrost mode, should the thermostat indicate that the strips are on in the display, either as "aux" or "emergency" heat?  I'm curious because mine did not. The lack of any indication when active in assist makes me wonder it there is a wiring or other problem.
Telling a man he has too many tools,
is like telling a woman she has too many shoes.
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#19
My programmable thermostat has 4 set points per day, in groups of 5 days for the work week, and 2 days for the weekend.  For air conditioning, I program it to step the temperature down by 1 degree every two or three hours during the night, to refresh the air in the bedrooms (2-story house with single-zone HVAC
Upset ).  Works quite well, actually.  Not as well as a separate zone for the upstairs, but that's just not going to happen.

Perhaps you could try something like that with your heat.  Step it up 1 degree and run like that for however long it takes on a cold night to catch up, then step it up another degree.  That's assuming a 1 deg. differential won't kick in the resistive heat, and that you have more than 2 programmable set points per day, of course.

I also program the heat to drop 5 degrees at night, as we like it cool for sleeping, but it's gas-fired warm air.  The heating system, not the occupants.
Raised

I know virtually nothing about heat pump systems other than the obvious, and would defer to those who do know.  But I would also try it, if it were me, because I try everything.  It's like an obsession.  
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#20
(03-27-2018, 06:42 AM)Terry W Wrote: Thanks all. Quick follow up question. If and/or when the electric strips come on as a heat assist or in defrost mode, should the thermostat indicate that the strips are on in the display, either as "aux" or "emergency" heat?  I'm curious because mine did not. The lack of any indication when active in assist makes me wonder it there is a wiring or other problem.

The ones I've seen all indicate when the when the auxiliary is active.
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.
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