Nest 3 connecting to two transformers

[stantons]

I have a Nest 3, a Carrier central AC system and a Burnham boiler.   The AC and the boiler have individual transformers 120v-24v.  If I connect heat side only with W, C, Rh, the thermostat works fine, 3.9 or so volts, 200ma, etc.  If I connect the air handler with Y, G, Rc, it does not control the AC.  If I connect the AC side only with Y, G, Rh, and C (this time C from the air handler) then the AC works fine.  If I connect the heat side with only Rh and W, problems arise:  If no call for heat then the there is massive short-cycling which stops once there is a call for heat.  I believe this is because the Nest is not getting proper power from the AC C wire.  This all may be because the Rh and Rc are internally jumpered.  I'm not really sure.   Can Nest 3 support both systems at the same time?  

[Marty64]

I have same question can't google answer??

[Ryan_G]

Hey folks,

Thanks for visiting the Google Nest Community. 

Since this thread hasn't had activity in a while, we're going to close it to keep content fresh.

If you have additional questions, feel free to submit another post and provide as many details as possible so that others can lend a hand. 

Hope this helps!

Kind regards,

Ryan