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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22541
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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I have a Honeywell PC 8900 that I want to convert to a Nest

Customer Question

Customer: I have a Honeywell PC 8900 that I want to convert to a Nest thermostat. I have 2 zones of hotter heat (floor and baseboard - the floor is main and the baseboard kick in as Aux heat if heat demand is more than 2 degrees) and I have a high velocity air handler for air conditioning
JA: Thanks. Can you give me any more details about your issue?
Customer: I want to convert the PC8900 thermostat and controller with a Nest unit and not sure how to wire it up
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Submitted: 1 year ago.
Category: HVAC
Customer: replied 1 year ago.
I have hot water heat system and high velocity air handler for air-conditioning in the attic, both are connected to the Honeywell controller PC8900 box, I have made a sheet showing the connections (see attached). I have wiring on W1 (floor heat) and W2 (baseboard - only kicks on when demand is more than air temp - if more than 2 degrees, the baseboard kicks in to get things within 2 degrees and then the floor heat W1 maintains the temperature) both are for the family room.I am looking for how to hook up the Nest thermostat (version 2 which has multi-zone/aux heat). I want to replace the PC8900 entirely so I can access/control the family room hear via the internet. I realize that I will lose the outside temp sensor as well as the remote sensor (which are present on the PC8900) as I don't really need that functionality.
Expert:  BillyHvac replied 1 year ago.


I apologize for the holiday delay.

Do you still need assistance?

Customer: replied 1 year ago.
I need to wire the new thermostat and am unsure how to do it due to the setup