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How to connect power connector to Carlin 90524a

Community Member

I recently purchased a nest thermostat that I want to use for heat only.  My current thermostat only has two wires and is low voltage.  I measured it at about 18 volts.  I connected the nest thermostat and it was working fine in terms of operating the heat but it gave me an error message.  When I research the error message it basically said that there wasn't consistent power and I needed to install a power connector.  The problem is that I do not know where to install it.  There is no c wire on the heating control unit.  There is a T1 and T2 terminal which go to the thermostat.  There are a bunch of other terminals on there but I believe they all have an output of 120 volts.  Can I just test the output of each terminal and see if one of them has 24 volt output and connected there?  If not is there some way I can install a transformer by the boiler and connect it there somehow?



Community Specialist
Community Specialist

Hi Fdibella,


Thanks for posting here in the Community forum and for showing interest in our Nest Thermostats. Your old thermostat has the terminals of T1 and T2 only making your system proprietary resulting to low power to the Nest Thermostat. Proprietary systems aren’t compatible with Google Nest Thermostats. However, some proprietary systems can be rewired by a pro installer to be compatible. 


On the other hand, you may learn more about the Nest Power Connector by checking on this article. 


Let us know if that helps.