Adding c-wire power to EWC BMPlus 3000 Rev B HVAC board

[Jackalope29]

I have a nest E and need to connect the C-wire. There is an unused wire in the bundle which I attached to the C connector on the thermostat side of the HVAC board. There isn't power coming through the wire. Do I need to connect something else?

Here is an image of the board before I connected the C wire.

https://photos.app.goo.gl/kpM6HuCnXxnAGmN8A

Thanks!

[Patrick_Caezza]

@Jackalope29 

How are you measuring the voltage?

If you use a multimeter and measure between the C and R terminals you should see 24vac

[Jackalope29]

 @Patrick_Caezza

Thanks! I reconnected things at the HVAC panel and measured 27v on the c and rc terminals and 20v at the thermostat. Hopefully that will do the trick. I will reply back when I install it tonight.

[Jackalope29]

 @Patrick_Caezza

I measured 19v at the thermostat wires between C and R, but the nest reports no c-wire. There was 27v at the HVAC panel. I will try the power connector and see if that fixes things. It seems like the existing c wire should have worked, though.

[Patrick_Caezza]

@Jackalope29 

19vac is too low and the thermostat won't work correctly.

Zone controllers typically don't have the available power needed to support any type of smart thermostat and you need to upgrade the power rating (VA) or use a separate transformer along with the Nest Power Connector.

[Jackalope29]

@Patrick_Caezza

Thanks again for the help!

I will try the power connector when it arrives and see if that fixes it. However, you suggest that I also will need a separate transformer too? Could you clarify that?

[Jackalope29]

@Patrick_Caezza

Thanks again for helping me out with this. I wish this was easier!

I installed the power connector today and get the N261 error. I still measure only 20v at the thermostat measured between C and R. I measure 27V between C and R at the thermostat side of the HVAC panel and 25v at the terminal side of the panel. The power connector test did not seem to work. It just ended with the power information but nothing about the connector being found.

Any ideas what to try next?

Here are pics of the HVAC panel before and after installing the power connector.

https://photos.app.goo.gl/9ujbKmTN3mwn1Vna9

[Jackalope29]

I got it working and I will post the solution in case anyone else runs into this problem.

Problem, only 20V at the thermostat on the C-R wire testing. 

27v at the C terminal and C thermostat side of HVAC panel. 

Wires correctly connected.

The issue: It turns out there is a splice in the thermostat wire somewhere between the HVAC panel and the thermostat. They did not connect the c-wire between the two sections.

Solution: rather than find the splice in finished basement ceiling, I just hooked up the power connector to the thermostat side of the HVAC panel. We have more than one thermostat and zone, but only use the nest on one. It worked without issue.

Bottom line don't assume that the wires from the HVAC panel go all the way to the thermostat without some random splice in the middle.

Hope this helps someone else!