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Dual fuel sensor hookup

Pdaroh
Community Member

I have a 3rd gen . Nest Learning Thermostat.   Our pro said that there was no place on the thermostat to hook up the outdoor sensor for our heat pump.  We have propane/ heat pump.  The thermostat does have a fuel fuel setting, so how do we attach the sensor?

4 REPLIES 4

Patrick_Caezza
Diamond Product Expert
Diamond Product Expert

None of the Nest thermostats have the ability to connect to external sensors at this time.


To ensure that I see your reply, please tag me using @Patrick_Caezza

CoolingWizard
Platinum Product Expert
Platinum Product Expert

@Pdaroh, your old HVAC system thermostat uses the outdoor sensor to make decisions of when defrost modes and measure system performance. The Nest Thermostat is very smart and uses googles Weather data from the Internet for your area to make those same decisions. 

What you need to configure for your duel-fuel heat pump system, is at what outdoor temperature do want nest to switch from Heat Pump heating to Propane Heating. 

There is a point at which it is more economical to use propane to heat your home compared to the heat pump itself. That point to switch over depends on how efficient or heat pump system actually operates at and how expensive is the propane is along with how efficient is your propane furnace is. 

A little experimentation is technically required at this point to determine the optimum temperature to switch over is. however if you contact a local HVAC company they can probably tell you what they would typically set the heat pump switch over temperature they use.  I bet it’s will be 25°F down to 20°F.

As for those extra two wires, just tape them up and stick them back in the wall

AC Cooling Wizard

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner.

Yes the sensor is set at 35 degrees to switch to emergency heat (propane).  There was no place to attach the sensor to the nest.  I would have to do it manually when the temps drop below 35 degrees.  I don’t want to worry about that so the sensor is needed.  

pereztzum
Bronze
Bronze

Hi @Pdaroh,

 

Thanks for posting on the community space.

We apologize that you're experiencing low temperatures. The Nest Learning Thermostat has a Safety Temperatures feature that keeps the temperature within a comfortable range (between 65°F and 70°F) based on your preferences. This feature prevents the temperature from dropping below a specific point, even if the thermostat is turned off.

 

To change the Safety Temperatures:

Press the thermostat's display to bring up the Quick View menu.

  1. Select Settings .
  2. Choose Safety Temp.
  3. Turn the ring to select the heating or cooling Safety Temperature you'd like to change and press the ring to choose it. Turn the ring to change the temperature and press the ring to confirm your change.
    • Note: You can disable a Safety Temperature by turning the dial to off when choosing a temperature, but we don't recommend this since setting a Safety Temperature helps protect your home.
  4. Choose Done to exit the menu.

 

Best Regards ,

Brandon.