Separate Thermostat for Boiler and Heat Pump - Lockout Temp?

[LawHoo]

I have a two zone Heat Pump system and a whole house Boiler.  Each unit is on its own separate thermostat.  There is not a heating pack (AUX heat) in the Heat Pumps, the Boiler is intended to be the AUX heat.  I would like to set a lockout temp for the two Heat Pump systems so that the Boiler will be the AUX heat when the outside temp is below 40 degrees.  (My significant other loves steam heat when it is really cold outside, not forced air.)

Problem:  I can't get an opportunity to set a lockout temp because the heat pump thermostats do not have a W1 wire connected to them.  My AUX heat is the Boiler, which has its own thermostat (the Boiler isn't connected to the Heat Pump thermostats).  Is there any fix other than just turning off the Heat Pumps when the weather starts getting consistently cold?  Thanks!

[Markjosephp]

Hello LawHoo,

Thanks for reaching out to the Google Nest Community. I'd be happy to take a look at this for you.

Your Auxiliary heat (AUX heat) is the backup method that many heat pumps use when the weather outside is too cold for the heat pump to work efficiently. Here's what I have found. Please check out this article with some Heat Pump Balance options that would be applicable for your adjustment and let me know if you have more questions.

Best,
Mark

[LawHoo]

Thanks, Mark, that was super helpful.  The trick is that, because I have a separate system and thermostat to provide the AUX heat (steam boiler), there is no wire to the W2/AUX on the thermostats that are hooked up to the heat pumps  (I have two separate zones for the heat pumps).  As a result, I don't see the Heat Pump Balance options at all on the thermostats that are hooked up the the heat pumps.  I'm wondering if there is a way for my HVAC guys to make the Nests recognize that there is an AUX heat source, but it isn't connected (say somehow hook the HP Nests to the AUX heat Nest so that I can set a lockout temp) or to use another setting so that they can set a lockout temp (outside of Heat Pump Balance).  I just need to be able to set a lockout temp so that the separate heating system (boiler) will do the job once the heat pumps stop heating.  I may just be out of luck here and will have to monitor the weather and once things start going below 40 and manually flip on the boiler and turn off the heat pumps.  Thanks again.

[Markjosephp]

Hey there,

I'm sorry for the late response, and I appreciate the details. The option would appear depending on the setup. Could you please share with us a photo of your thermostat's wiring? Also, try restarting your thermostat and checking the Nest Sense settings or the Equipment Settings for the Heat Pump Balance option to see if it appears.

Regards,
Mark

[LawHoo]

No worries, Mark, I appreciate the help.  I cannot attach photos of the wiring from the Nest App because I don't have permission.  Here is a link instead:  https://www.dropbox.com/t/4rdqccLEovMupu6C

There is not AUX heat as part of the heat pump, so I'm not going to get Heat Pump Balance to appear.  The system is more like a dual fuel system, but the heating source is on a separate thermostat.  I'm wondering if we reroute the heating wire (W) from the currently dedicated heating thermostat to the two heat pump thermostats (W2 AUX), that would show me the option to set a lockout temp.  I would also need to know if we would need to run the power wire (W1) from the boiler thermostat to the RH of the two heat pump thermostats.  Thanks again.

[Markjosephp]

Hi LawHoo,

Thanks for the photos. Heat Pump Balance controls AUX heat. Since you don’t have AUX heat, Heat Pump Balance won't appear as an option. In addition to the Equipment options, can you share with us other photos of the options available on your actual thermostat's Equipment settings? 

Keep me posted.

Best,
Mark

[Markjosephp]

Hello LawHoo,

Checking back in — how's it going? Still need our help?

Thanks,

Mark

[LawHoo]

I do still need assistance.  I've done some other research and it looks like I may need to abandon the notion of a separate thermostat for the boiler.  If I do that, would I be able to wire the two HP thermostats in parallel with the boiler?  I would think that would allow me to set a lockout temp for the HP and then the boiler would kick in when either one of the HP thermostats called for heat.  Given the two zones are pretty close, I'm thinking that I'm not going to see much around cycling.   Thanks - Dan

[Markjosephp]

Hello Dan,

I know it has been a while, but I wanted to ensure that everything was covered here.

Got it. The best possible option is to reconfigure your HVAC system wires and use your Nest Thermostat as the primary control for your Zone system. By doing this, it could still use the lockout temperature or auxiliary heat, depending on the setup process. Let us know if you have more questions.

Thanks,
Mark