Nest App shows Offline during heat pump defrost

[ECODE]

Have a Bosch heat bump and matching gas furnace. 

Y1, OB connected for heat pump 

W1 for furnace (alt heat).

G (fan), C (24V), Rc (power) 

Everything works well, except when the heat pump goes into defrost mode, the nest app will think the system is offline... It isn't, the thermostat is still connected and has strong Wi-Fi when I look at it on the wall... 

Is this normal? There's no wire from the heat pump back to the thermo to denote defrost mode, and the alt heat doesn't come on during a defrost event either (I'm lead to believe that this is something that's sorted between the heat pump and the furnace, without the thermostats involvememt anyway). 

Any ideas if this is normal?

[Markjosephp]

Hello ECODE,

Thanks for reaching out! It seems like your Nest Yhermostat setup is generally correct, with Y1 and OB connected for the heat pump, W1 for the furnace (alternate heat), and G, C, and Rc for fan, 24V, and power, respectively. The issue you're experiencing with the Nest app thinking the system is offline during the heat pump's defrost mode can be a bit perplexing.

In a typical heat pump system, during defrost mode, the heat pump temporarily switches to cooling mode to melt any accumulated frost on the outdoor coil. This can cause a brief interruption in heating, but the auxiliary heat source (the gas furnace in your case) should kick in to maintain warmth.

The fact that there is no wire from the heat pump back to the thermostat for defrost mode indication is normal, as this information is usually handled internally between the heat pump and the furnace without direct thermostat involvement. Check the settings on your Nest Thermostat to ensure they align with the specifications of your heat pump and gas furnace. Sometimes, adjusting certain settings can improve system behavior.

Regards,
Mark