Nest show error code "no power to Rh, but 24 VAC is present on Rh wire.

[rgaila]

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Original Poster: Dick A 

Nest show error code "no power to Rh, but 24 VAC is present on Rh wire.  HVAC professional says thermostat is dead.   Any suggestion?  I saw a thread similar about a year ago, but no resolution.

[rgaila]

Hey Dick,

Running into error codes can be a little troublesome, I am sorry this is the case here. Let's jump in and see if we can resolve the issue, and get you up and running. I would recommend turning off the breaker and trying to swap the Rh wire to RC. Once done, turn the power back on and see if that works out. Let me know, so I can ensure you are good to go.

-From Jake K, Community Specialist.

[island11558]

Hi Jake,

I cannot follow your instructions, as they make no sense.\

1) my system was set up > 2 years ago and worked fine until this Rh no power issue

2) the Rc wire is from my central air conditioner

3) the Rh wire is from my heating system

so I have no idea why I should switch them without a much more detailed description of why you would want me to do that

I have solved the problem of no power when using cooling by having a C wire dropped to the thermostat from my AC system

I have used a kluge to solve the problem of the google nest thermostat showing no power to Rh by removing the two heating wires and installing an old fashioned honeywell round thermostat for heat.  Judging by the unreliability of this nest gen3 learning thermostat and the inability of google to determine why a wire that shows 24V to a meter doesn't show power at the thermostat, I will probably just change the cooling portion to the honeywell thermostat in the spring.

Oh well. so much for google nest technology, better to go old school than to have the pipes freeze

[Dc21]

I totally agree with everything you said. 
I had the same issues with my nest thermostat that I bought less than a year ago. I emailed, I called, and I chatted with a nest specialist. No one had a single answer why there was a error with the wire. 
I got so frustrated that I called HomeServe technicians and they came checked the power which had no problem whatever. They removed the nest thermostat and replaced  it with Honeywell thermostat. The nest thermostat it is a big scam and their costumer services is horrible.

[jgreen110715]

Hi Jake I too am having this same issue. Same wiring and thermostat for last almost 3 years. Don't understand why now it's not working. House dropped to low 60s and I have a small child in my home. This is unacceptable especially when I can prove the power is there.

[Barrie]

I have the same problem.  
recently my 3rd gen net learning thermostat stopped working (set to cool) due to battery dead.  FWIW, This is after working fine with no change in the wiring for over two years.  After recharging it shows Rh wire present but not connected. A power meter shows good 24V, and crossing Rh with W1 turns on heat.   It continued to go battery dead when still set to cool. Error code N72.  I restripped the wire and reinserted it properly and the tab to stays down

I had a C wire installed and the thermostat keeps a charge now. It also works the AC cooling fine.  It still shows Rh connected but no power. Still shows . Error code N72

I am leery of heeding your advice to change the RC and Rh wires however.  That would seem to cause the heat to go on when the unit calls for cool I’m guessing.  Unless there’s another step after that?  perhaps you meant switching the W1 and Rh wires??  If the thermostat was miswired, It certainly doesn’t explain why this occurred out of the blue after working fine for two years. 

when the thermostat is switched to heat and it calls for heat, the TACO box that controls the zones just clicks and clicks without initiating heat

FWI

Wires to thermostat

Y1, G, Rc, W1, C, Rh

gas fired hot water heat, one of three zones

AC separate system, central air, fan goes when cooling only and only one zone

whatever the case, now that it’s September I’ll be needing heat soon and it seems I’m heading toward a regular old fashioned thermostat for that…

[CaptainJeff]

I am currently experiencing the same problem (when the thermostat is switched to heat and it calls for heat, the TACO box that controls the zones just clicks and clicks without initiating heat).  Installed Nest Gen 3 in April 2021.  Controlled heat through at least early May and then transitioned to A/C mode.  Was getting ready for the winter (New England) and set back to "heat" mode to test - that's when I experienced the TACO box clicking and N72 code.  PM visit from HVAC Tech yesterday confirmed issue in the Nest.  I chatted with a Google Nest person and they are shipping me a new baseplate.  I won't know if that will solve it until I get it and reinstall.  

[CaptainJeff]

I have the same exact problem.  Installed Nest Learning on 1 April.  Ran heat through May, then AC and Heat into June until we went to straight AC for summer.  Multizone heating system (forced hot water) with two Nest E's on other zones.  Testing heating system from Nest Learning on 6 Oct.  Taco box just kept clicking.  You will see other posts about this across the web.  Call heating company for PM b/c I assumed the problem was with boiler.  First thing tech said when he arrived was "you have a Nest thermostat, correct?".  He performed the same troubleshoot you did (W to Rh wire - triggered heat).  Notified Google and then sent me new baseplate (arrived last night and installed - no fix.  Same exact issues).  Contacted them again this morning and just went through 2 hours of painful chat troubleshooting with totally useless reps (Madison and then Enzo).  If you get them, stop the chat, pull the Nest out of your house and get another brand.  I'm done with having a teenager in their basement ask me if my house is powered and calling it support/troubleshooting.  

[CaptainJeff]

Same issue here happening now.  No solution from Google but they are trying to keep carrying me along as my house temp drops.  23 days and no ability to heat 

[Kdoll]

Any new solutions? I posted about a similar issue a while back. Have a C wire and the Nest works fine with the AC but my Rh wire shows up grayed out. Thought about getting a HVAC person to come up take a look but have a feeling they won't be able solve it. Someone mentioned it could be faulty Nest but seems like the new baseplate didn't work for you?

[sidney87]

I have no idea what happened  It just says not connected to wifi rh