Anyone else using a nest thermostat with the heatpump and propane hot air furnace?

[Mb190e]

I just installed the new nest thermostat and had a heat pump installed with propane hot air furnace. My installer had a couple questions about the thermostat after we got it set up. if the heat pump can't satisfy the thermostat after a period of time does the propane furnace turn on? Which would be the same scenario if the heat pump failed, would be propane furnace turn? And the other question was when the heat pump goes into defrost mode basically running the air conditioner does the propane furnace come on so you're not blowing cold air into the house?

Scott

[Willy T]

Congratulations on your install. I don't have a Nest, but I can tell you how it works on a Honeywell, You choose Heat Pump with Fossil Fuel Backup.

1) Balance Point, the Balance point is where the HP unit would shut down and the Furnace would take over based on the Outside Temperature. Most Installers set it to 30° or so. I have mine set to 20°, but you'll have to see what the gain or loss is for your house and where you are comfortable and what fuel is the cheapest. I think you are like me with plenty of KWH banked, I tried 15°, it was ok on heat, but ran a lot and used up KWH pretty fast. So it's something you'll have to test to find whats best.

2) Droop Control, the Droop control is a setting that controls the amount of drop in temperature of the return air sensor that will trigger the furnace to come on, usually set to 2°. Maybe done by the thermostat, if you don't have the sensor.

3) Furnace Upstage, the Furnace upstage is a time that the heat Pump can run without the furnace coming on to assist in reaching the set limit on the Thermostat set room temperature, usually set at 1 Hour.

** The Droop Control and Furnace Upstage can be disabled if not needed. ( I don't use either )

Defrost, when the heat pump goes into defrost the furnace will start. The only issue here is that the furnace takes time to light and heat up before you get any heat in the defrost mode. If you have a more efficient furnace with a flue blower that also will add time until you feel any heat. maybe there are thermostats that have a way around this to pre-heat the furnace, but I don't know if there are.

[Mb190e]

In the nest I only have the balance point. so I either have the heatpump that runs or the furnace that runs. I currently have the balance point set at 40°. I do not have any of those other settings. I can't confirm this but I think during the defrost mode we are going to have air-conditioning blowing in the house. What Honeywell thermostat you have? I'm looking for a Wi-Fi connected thermostat that can handle dual fuel heat pump, propane hot air furnace and air conditioning that I can control from my iPhone or iPad. Looks like I'm going to be returning this Nest as soon as I find a thermostat that works.


Yes I'm looking to burn up my extra kWh's with the heatpump and save some money on propane. I currently have about 2000 kWh's in the bank after three months.

[Willy T]

I don't have a fancy one, Honeywell has plenty with wifi. Mine is a TD6220 ($70 ). The fancy ones are about $200. I don't do well with touch screens, I try to keep it simple.

https://www.acwholesalers.com/Honeywell/THX9421R5021WW-Prestige-Color-Touchscreen-Thermostat-w-RedLINK-White/33230.ac?gclid=CKG3rsaF678CFWELMgodCiwANw

The Nest may just consider the backup heat as electric. They have a forum on their site that I'v looked at before and some user groups you might want to check out before you give up on it.

You may have better luck here.

https://community.nest.com/welcome

[Mb190e]

thanks, I posted the same question on the Nest community forum. I found a couple other people with the same issue over there. I found this thermostat http://www.amazon.com/Honeywell-TH83.../dp/B009XC4JYE which is $100 less than the nest and is supposed to do dual fuel like you're saying. And it's wifi.

[inetdog]

In the nest I only have the balance point. so I either have the heatpump that runs or the furnace that runs. I currently have the balance point set at 40°. I do not have any of those other settings. I can't confirm this but I think during the defrost mode we are going to have air-conditioning blowing in the house. What Honeywell thermostat you have? I'm looking for a Wi-Fi connected thermostat that can handle dual fuel heat pump, propane hot air furnace and air conditioning that I can control from my iPhone or iPad. Looks like I'm going to be returning this Nest as soon as I find a thermostat that works.


Yes I'm looking to burn up my extra kWh's with the heatpump and save some money on propane. I currently have about 2000 kWh's in the bank after three months.

That balance point temperature is probably way too high, especially using high cost propane instead of low cost natural gas as the fossil fuel.
Your heat pump should still be working very well at an outside temp below 40.

[Mb190e]

Well I returned the nest thermostat I have a Honeywell-TH8320WF1029 on its way to my house. I agree with the 40° balance point. But my opinion is only based on what I've read about the temperatures other people are running the balance point. Inetdog, what temperature for the balance point do you think I should start? Location 12866

[inetdog]

Well I returned the nest thermostat I have a Honeywell-TH8320WF1029 on its way to my house. I agree with the 40° balance point. But my opinion is only based on what I've read about the temperatures other people are running the balance point. Inetdog, what temperature for the balance point do you think I should start? Location 12866

I would look at the output versus outdoor temperature curves of your actual heat pump and then look at how much maximum heat generation you would likely need at each outside temperature. (That may very well change with time of day, so choose a representative worst case number.)
Find the temperature where the heat produced falls below the heat needed and then set the balance point a few degrees above that.
Willy T has suggested 30 degrees as a consensus value among installers in his area. Your conditions may vary!
If unable to get the needed curves and figures, I would set it very low (maybe 20F) and then check to see whether the pump is unable to maintain the set inside temperature as the outside temperature gets closer to 20F. Adjust as necessary.

[Willy T]

Here is a small chart, there 1000's on the Internet, but this will show you the expected output at a given outside temperature. Basically if your at 36,000 btu @ 40° F then @ 20° you'll have 29,000 btu and so on ( not exact ). The problem is the thermostats are in 5° increments ( balance points ). A lot is location and the heat loss in your house. You'll have to test it and see where yours needs to be. You may have to change it to a different setting during the coldest months.

Here is something you could do, add a electric heat strip to your furnace plenum that is triggered by a outside thermostat. Say you set the change over to gas at 20°, you could have the heat strip to come on with the heat pump at 25° and that would increase you heat output. Once you went to gas the heat strip would be out of the loop. This would also take care during the defrost cycle.

ScreenHunter_832.jpg

[Colt45]

I have installed some of the units you have on the way. You will need to configure it via menu numbers and settings. It is a good unit but some have a LOT of options to set and some options only show up based on if other options are enabled or not. Look at the directions and understand them before you program it.

If you run into problems they have good phone support that can help you out.

Also keep in mind that the color of your wires means nothing... You need to know what each is for. Yes there is a "normal color code" but that is often violated due to strange configurations.

Good Luck!!!!

[Mb190e]

I have installed some of the units you have on the way. You will need to configure it via menu numbers and settings. It is a good unit but some have a LOT of options to set and some options only show up based on if other options are enabled or not. Look at the directions and understand them before you program it.

If you run into problems they have good phone support that can help you out.

Also keep in mind that the color of your wires means nothing... You need to know what each is for. Yes there is a "normal color code" but that is often violated due to strange configurations.

Good Luck!!!!

Colt45 could you help me out with this new thermostat TH8320WF I have it wired.

Red-R with jumper to RC
Orange-O/B
Yellow-Y
Green-G
Blue-C
White-E/Aux
S1-outdoor temperature sensor
S2-outdoor temperature sensor

I can get everything to work individually but I can't get it to automatically switch over from the heat pump to propane when I'm more than the droop setting. so I tricked the outdoor thermostat into thinking it was 55° out with ice water, so that it would run the propane furnace when I set the thermostat 10° higher than it was currently in the house.

My settings on the thermostat are.

0170-7
0173-0
0190-0
0200-1
0210-0
0220-3
0250-3
0340-2
0346-1
0347-2°
0350-35°
0360-65°

If you have any ideas that would be great thanks.

[Colt45]

That may be correct operation, depending on what you have it set for. Depends if you have it for "emergency heat" or "2nd stage" Can you provide a link to the T-stat manual?

What are the inside a outside temps now in your area?

Also what tells your propane burner to come on? Do you have a separate wire directly from it or does the heat pump call it with a controller?

[Mb190e]

Colt45, sorry I never responded to your questions. I got tired of messing with thermostat trying to get the heat to work, tricking the thermostat in the middle of summer. Now that it's in the high 30s low 40s the last couple days it appears I have all my settings correct and the thermostat is working properly. Making heat with the heatpump.  If there's more than 2° between call temperature and current temperature propane furnace comes on and heatpump does not run. Looks like it runs just over 3 kWh's per hour to heat with the heatpump. Right now I have 3100 kWh's in the bank.

[bcroe]

Colt45, sorry I never responded to your questions. I got tired of messing with thermostat trying to get the heat to work, tricking the thermostat in the middle of summer. Now that it's in the high 30s low 40s the last couple days it appears I have all my settings correct and the thermostat is working properly. Making heat with the heatpump.  If there's more than 2° between call temperature and current temperature propane furnace comes on and heatpump does not run. Looks like it runs just over 3 kWh's per hour to heat with the heatpump. Right now I have 3100 kWh's in the bank.

I avoided that issue on my heat pump installation 2 weeks ago. I specified the heat pump
have its own thermostat, completely independent of the propane furnace. The only thing
they share is ability to turn on the air mover blower. I can turn either completely off, or
set them to entirely different temperatures.

There was no way I was going to risk that gee whiz touch screen thermostat failing and
taking down my propane backup system (which can be generator powered if needed). My
anvil reliable tilting mercury thermostat runs the propane. Bruce Roe