NEST Thermostat

ScottCyr

I bought a Nest Thermostat for my oil fired boiler which runs a First Co Air Handler. The AC portion fires on/off and works fine. However, the heating side does not work. It does not activate the heat demand on the pump relay, etc. Voltage at the Nest is about 8v (AC) on Rh, Rc, Y, G, W.

Nest tech service says the voltage needs to be higher, closer to 24v.



Is there a way to "boost" the voltage from the boiler tt or air handler tt to increase the voltage at the stat?



Surely other issues have been solved easier.

Robert O'Brien

Rc and Rh?

Are separate? Zone valves or pumps on boiler? How is blower turned on during a heat call?

ScottCyr

Rh Rc have a built in jumper

Thanks for the response. Sorry for not mentiuoning the full details.

Boiler has pumps controlling the zones.

Rh turns the fan on at the blower.

Old tstat had a jumper between Rh and Rc but Nest says this is built into their wiring and it does not need it.

ScottCyr

PROBLEM SOLVED

It was a simple enough fix but did require a call to First Co Tech Support.

1. On the First Co air handler, use C1 and connect to C on the Nest. This will give the Nest the correct voltage (not mentioned in the install guide by the way)

2. The jumper is not needed between Rc and Rh as Nest has a built in jumper. However, Nest fails to mention that you do not need to connect ONE of these wires, most likely blue, but trace your wires back and see what they are connected to. I left Rh off of the Nest (although it was connected to the old tstat along with a jumper to Rc).

The Nest works fine now in both heating and cooling mode with an oil fired Slant Fin Eutectic and Grundfos Alpha pumps. I also installed the new Spirotherm Air/Dirt Separator. The system shows a lot of dirt in it. I am looking forward to seeing it get cleaned up.