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Nest E adding in 24V

Community Member

Morning Everyone,

Just installed a new Brivis Buffalo BX326 Ducted heating system and this is how the old unit was wired.
However now my W and R wires do not contain power at all, when joining these wires together it turns on as expected.   However when connecting the nest the unit turns on all the time.
There is a 24V AC Transformer inside the unit which i can get to and run to the unit.
Just unsure of the wire locations.  I see all the diagrams are for Nest power conector.


I Have seen some base plates have a C and RH Connector which can be used to run 24V.
However my unit does not appear to have these locations. 




Community Specialist
Community Specialist

Hi epicfatigue, 


Thanks for posting here in the Community forum, and I'm sorry to hear about the situation. Let me take a look at this for you. 


Please send us a photo of how the thermostat wires are connected to your previous thermostat wires and a photo of how the thermostat wires are connected to the HVAC control board. Also, please gather the power readings of your Nest Thermostat E by going to its Settings > Technical Info > Power (Battery, VOC, VIN, and lIN).


I'll look forward to your response. 




Community Member

Hey Zoe I see a few people had this problem after reading the forums but no answer was ever provided.


I have since resolved this and forgot to update this post for the rest of the community.


My unit contained a W wire and a R wire.


24v AC across them, and bridging them would result in the heater on.  My older heater had no issues with these two wire however this unit is very sensitive, guessing it uses an op amp, and the draw from Charing the nest was enough to bias it. 


I fixed it by doing the following.


Alot of units have the Neutral connected to the heater (metal of the heater) you can verify this by checking voltage between the heater and the R wire and seeing if you have 24v if you do just run a wire from the metal of the heater to the C slot of the nest. This will provide a common neutral. 


If there isn't 24v then just run a wire from the Neutral of the Transformer.  ( Only if you know what you are doing) 




Hope that

helps people. 


Community Specialist
Community Specialist

Hi there, 


Awesome! I'm glad that everything has been sorted out, and I appreciate your sharing the steps you took to resolve this case. If you have questions or concerns in the future, feel free to start a new thread, and we'll be happy to help.