Alternate heat setting

[Fierodough]

Please help!

I have a Bosch IDS heat pump, propane furnace and heat exchanger. (All Bosch IDS)

the heat pump can upstate to -22*C. 

the setting in the Nest thermostat to activate Alt Heat only goes as low as -12*C. 

can this be fixed or adjusted so that I can take full advantage of my heat pump this winter as propane is very expensive here. 

For more clarification my configuration is as follows for heat:

Heat source 1: Electric (heat pump)

Alt heat source 1: propane (stage 1)

Alt heat source 2: propane (stage 2)

All heat types are forced air. 

[zoeuvre]

Hi Fierodough, 

Yikes! I'm sorry for the delayed response—let's see what's going on. 

Heat pump outdoor units can easily freeze over during the winter. If the temperature is too low, ice may have gathered on the device. This obstructs airflow and prevents heat absorption. So in order to prevent this from happening, your thermostat will switch over to using your ALT heat to warm up your home. To get a better understanding, see this heat pump balance guide for more. 

Let us know if you have any other questions.

Best,

Zoe 

[Fierodough]

Hi Zoe,

i don’t think you understand my question. My Bosch IDS 2.0 system has a heat pump designed to operate at up to -20*C or -4*F. It is able to thaw itself, it has a defrost system. It is made for the harsh Canadian winters. 

if I use the Bosch thermostat, there is no problem. It will keep using the heat pump until the weather outside gets close to -20*C. Same with the Ecobee. But with the Nest, I can only

go as low as -12*C before the Nest engages aux heat. 

How can I fix this?

thank you. 

[Byronpilon]

Hello did you get an answer ???  I was thinking the same and would like to adjust -12 to -20.   #

[Danzeword]

I did but haven't changed anything. My gas furnace starts for the defrost process and it's only for about 5 mins every couple of hours. So not an issue anymore. I've set use alternate to Never as my heat pump is rated to -35 celcius.

[Danzeword]

Good day,

I have the same issue. I've set my thermostat to never use Alt source.

But it has been turning my gas furnace on as soon as the temperature is at 0 Celcius.

No ice had accumulated and my heat pump is rated to -35 C.  I was recommended the ecobee to fix this issue. Hopefully Google will have a fix for this at some point.

[zoeuvre]

Hi folks, 

I am sorry for the late reply. 

@Fierodough, the actions you talked about concerning the Nest Thermostat turning on extra heat at minus 12°C are most probably because of the difference in temperature settings and the special ways that Nest uses to figure out when to start extra heat. Nest Thermostats come with special rules. These rules target balance between energy use and comfort. They look at things like how hot it is outside, how hot it is inside, and how quickly the temperature inside is changing.

If you like the Nest Thermostat to only use the heat pump until it gets really cold at -20 degrees, you might have to change the how-hot-it-needs-to-get settings in the Nest Thermostat's setup. Remember that changing these settings might make a device use more energy. It could lead to heat pumps running for longer in cold weather or using more power overall. To change how hot or cold the Nest Thermostat is, you can get to the settings by using the device's menu or the Nest app. Search for choices that temperature differentials, heat pump balance, or auxiliary heat lockout. 

@Danzeword, if your Nest Thermostat is set not to use gas furnaces and you're facing them turning on even when the temperature is 0°C, there might be another problem causing this. Here are a few steps you can take to troubleshoot the situation:

1. Check your Nest Thermostat settings to make sure it's set to "Never" or "Off" for auxiliary heat (gas furnace). Make certain there are none settings or plans against it and not let the gas furnace turn on by mistake. Go to Settings > Equipment > Heat Pump.
2. Check that the wiring from the thermostat to your heating and cooling system is set up right and securely connected. Sometimes, messed up wiring can cause unexpected actions or problems between various heat sources.
3. Check that your Nest Thermostat works with your special heating and cooling system, including the heat pump and gas heater. You can tell us the make and model of your system so we can take a closer look on it. 

Let us know if that helps.

Thanks,

Zoe

[Danzeword]

Thanks Zoe, now I would like to know this. Where is the " how-hot-it-needs-to-get settings in the Nest Thermostat's setup". From your instructions above "Search for choices that temperature differentials, heat pump balance, or auxiliary heat lockout." The only thing I see in the app or the Device is Dual Fuel where the settings down to -12 is the lowest we can go for alternate fuel. Is this setting you are talking about in the more advance installation features under nest pro?