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Old 04-12-2012, 01:27 PM   #1
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Thermostat recomendations for hybrid Gas/electric heatpump?


Hey folks!

I recently bought a Goodman Gas furnace with Electric heatpump package. so I'm on the hunt for a good thermostat that will work with this system.

I found these 2 Honeywell units, and was wondering any opinions on them. both seem like they would work for my system, but I just want to make sure. also wondering if anyone has used either of these before and have any likes or dislikes.

honeywell IAQ
http://customer.honeywell.com/honeyw...x/YTH9421C1010

Honeywell Prestige (seems to be pretty high end, and I can find it for around $75 more then the first one)
http://customer.honeywell.com/honeyw.../ythx9421r5069

Any thoughts or recommendations would be most appreciated.

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Old 04-12-2012, 09:21 PM   #2
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Thermostat recomendations for hybrid Gas/electric heatpump?


The HD is the better stat. Either will work fine with your system.

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Old 04-12-2012, 09:51 PM   #3
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Thermostat recomendations for hybrid Gas/electric heatpump?


Installed both, like both, own the vision Pro. The prestige can do more, but for the money............
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Old 04-17-2012, 01:10 PM   #4
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Thermostat recomendations for hybrid Gas/electric heatpump?


Do either of these thermostats support shutting off the heat pump when the 2nd stage gas furnace is on? Looking at the manual, it doesn't look like they do. I have the VisionPro TH8320 right now and it doesn't do this, which is a huge problem as the furnace and heat pump/compressor running at the same time causes the pressure in the heat pump pipes to go too high (we believe this is what caused a leak last year... $1200 in damage). Right now I've just configured the furnace as EM (emergency heat), and so there is no Auxiliary heat. This is not acceptable though because the heat pump can't bring the temperature in the house quite high enough to be comfortable. Anyways, I need a thermostat that can switchover to auxiliary heat when required, but shut off the heat pump so that the two aren't running at the same time.

drnick5: you may want to look into this... do you have a indoor coil that is right next to the gas furnace and sitting on the hot side rather than the cold side? This is a problem. Read this page: http://www.refrigerationbasics.com/1...eat_pumps2.htm. He doesn't mention the damage this can cause, but just mentions how it doesn't make sense to have them both running at the same time.
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Old 04-17-2012, 01:43 PM   #5
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Thermostat recomendations for hybrid Gas/electric heatpump?


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Old 04-17-2012, 03:43 PM   #6
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Thermostat recomendations for hybrid Gas/electric heatpump?


The TH8320 shuts off the heat pump when the gas furnace comes on. if its been set up right. Yours isn't set up right if its allowing both to run. Other then during defrost.

Both the IAQ and HD shut off the heat pump when they call for the gas furnace to run, when they are set up right.
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Old 04-17-2012, 04:04 PM   #7
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Thermostat recomendations for hybrid Gas/electric heatpump?


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Originally Posted by beenthere View Post
The TH8320 shuts off the heat pump when the gas furnace comes on. if its been set up right. Yours isn't set up right if its allowing both to run. Other then during defrost.
Thanks beenthere

I guess I might as well hijack this thread. Maybe this is useful to the OP as well...

I have mine set up as follows:

E - emergency - connected to gas furnace right now
Aux - auxiliary - was connected to gas furnace, not anymore
O/B - changeover valve - connected to heat pump
Y - compressor - connected to heat pump
G - fan - connected to gas furnace

There is a note about "Install field jumper between Aux and E terminals if there is no emergency heat relay." The Aux and E terminals have never been jumpered before.

When I had Aux connected to furnace (original installer had done this), the furnace would come on when necessary but the heat pump would be on as well. How do get the heat pump to shut off? The repair person changed the wiring as a safety measure for now, so that the E connects to the furnace. So now the furnace never goes on unless I switch to EM mode manually. This was done to prevent another burst in the pipes due to high pressure.

The two options in the thermostat's control that I don't really understand are options 200 (auxiliary heat) and 210 (external fossil fuel kit). 210 seems simple enough, since I don't have an outdoor temperature sensor it has to be set to 1. But 200 just says "electrical backup heat (1)" or "fossil fuel backup heat (0)". I understand what electrical and fossil fuel means, but how does that affect the operation?

Then there is options 350 and 360. These set lock-out temperatures. Again, not really what I need exactly (I don't think).

Another option I guess is "System type". I'm pretty sure mine is set to "2 heat/1 cool heat pump (with aux. heat)". Other possibilities are "2 heat/1 cool multistage conventional". I don't really know what that means. But I don't have a multistage furnace, if that's what that means...

Any help on configuring TH8320 to shut off heat pump while auxiliary (gas furnace) is on?

Last edited by djgrant; 04-17-2012 at 04:16 PM. Reason: minor clarification
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Old 04-17-2012, 04:17 PM   #8
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Thermostat recomendations for hybrid Gas/electric heatpump?


200 set to 1
210 set to 0

Need the outdoor sensor, its 20 bucks or so.

Some of the older models, you could get a way without the outdoor sensor.
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Old 04-17-2012, 04:28 PM   #9
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Thermostat recomendations for hybrid Gas/electric heatpump?


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200 set to 1
210 set to 0

Need the outdoor sensor, its 20 bucks or so.

Some of the older models, you could get a way without the outdoor sensor.
Option 210: External fossil fuel kit:
1 External fossil fuel kit controls backup heat
0 Thermostat controls backup heat (outdoor sensor required)

Oh crap, I think I get it now!!! When set to 1 it assumes that there is one of those fancy "fossil fuel kits" installed and so it assumes that the fossil fuel kit will handle the shutting off/on of the backup heat and the heat pump. I don't have a fossil fuel kit, so that doesn't make sense to use that option...so is that why I'm getting weird behaviour?

So if I set it to 0, it will energize Aux but not the compresor (Y)? Why does this option require the outdoor sensor? What does the exterior temperature matter?
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Old 04-17-2012, 04:30 PM   #10
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Thermostat recomendations for hybrid Gas/electric heatpump?


Outside temp is required to st lock out temps for heat pump and gas furnace.
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Old 04-17-2012, 04:32 PM   #11
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Thermostat recomendations for hybrid Gas/electric heatpump?


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Outside temp is required to st lock out temps for heat pump and gas furnace.
Right, but why do I need to set lock-out temps just to prevent the auxiliary heat from running at the same time as the compressor?
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Old 04-17-2012, 04:46 PM   #12
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Thermostat recomendations for hybrid Gas/electric heatpump?


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Originally Posted by djgrant View Post
Right, but why do I need to set lock-out temps just to prevent the auxiliary heat from running at the same time as the compressor?
You don't, at least on the older versions of the TH8320. However, at 50 outside if you raise your indoor temp by 2 degrees, it will bring on the furnace, which cost more to operate, unless you have the outdoor sensor and set up the lock outs.

I seldom use that model anymore, since the IAQ isn't that much more money, and has much better control of dual fuel systems.
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Old 04-17-2012, 05:24 PM   #13
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Thermostat recomendations for hybrid Gas/electric heatpump?


Quote:
Originally Posted by beenthere View Post
You don't, at least on the older versions of the TH8320. However, at 50 outside if you raise your indoor temp by 2 degrees, it will bring on the furnace, which cost more to operate, unless you have the outdoor sensor and set up the lock outs.

I seldom use that model anymore, since the IAQ isn't that much more money, and has much better control of dual fuel systems.
So if I understand you correctly, if I have setting 210 set to 0 as you said, then the heat pump will shut off when the furnace goes on, regardless of whether or not I have set any lockout on setting 350, but assuming I have installed the outdoor sensor.

It sort of makes sense I guess. The behaviour of the lockout for fossil fuel (setting 350) says: "Heat Pump Temperature Lockout (with fossil-fuel backup): If the thermostat is installed with an optional outdoor sensor, you can select a compressor lockout temperature (Function 0350). When the outdoor temperature is below the lockout temperature, only the auxiliary heat operates. When the outdoor temperature is above the lockout temperature, only the compressor operates."
So in this lockout temp situation, there is an interlock between the two and only one is allowed to operate at a time. And then if I set the 350 lockout setting to off, there is no lockout temperature, but they still operate in the mutually exclusive way. Am I getting this right?

Thanks.
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Old 04-17-2012, 05:52 PM   #14
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Thermostat recomendations for hybrid Gas/electric heatpump?


Yep, your getting it now.
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Old 04-17-2012, 05:55 PM   #15
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Thermostat recomendations for hybrid Gas/electric heatpump?


It's so confusing because in one case it implies a fossil fuel kit is required, and the other implies an outdoor temp sensor is required. I have neither, although the "outdoor sensor" option seems more sensible (assuming I install a sensor)... it would be nice if Honeywell explained what exactly each option did, or if they had a flow chart explaining the algorithm that the device is running.

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