Nest -- No power to Rh, multimeter checks out


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Old 09-30-18, 06:45 PM
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Nest -- No power to Rh, multimeter checks out

I have a similar issue to this thread, but no common wire:
Nest- no power to Rh with common connected

Nest is setup and get the "no power to Rh, e24" error.

My old thermostat (Honeywell RTHL2310B) was only hooked up with two wires, W and R. When I check the connection between them with a multimeter, I see 26V.

Anything obvious to try?
 
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Old 09-30-18, 08:39 PM
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Welcome to the forums.

The way a nest works without a C wire is it steals a charge from being connected in series with the load. Several companies use this method. It's a 50/50 crap shoot if it works correctly. Most pro installers won't connect it without a C wire. I don't.

Are you stuck with the two wires ? It will work with three.
If you're stuck.... I need to know what it's connected to at the other end.
Boiler..... zone valve, aquastat, etc
Furnace... control board part number.

As a test..... you could connect the nest and check the voltage on those two wires. You may have to do it at the source end.
 
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Old 10-01-18, 05:46 PM
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Hi, Pete! Thank you for the warm welcome.

I took a look at the situation in the basement. The house is very old and the wiring situation is pretty funky. There are three wires leading to the thermostat, but inspection in the basement revealed only two of them actually lead to the boiler. The third wire just ends nearby, connected to nothing.

We have a Weil-McLain EG/PEG-65.

Do you think the only issue is wiring a common? It shouldn't be hard to do this given that the third is already run through the floor for me.
 
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Old 10-01-18, 08:40 PM
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The link below should cover your manual. It shows that the entire metal case is grounded and the C from the transformer also connects to the metal case. What you need to do it to find where the two stat wires connect to the boiler controller with wire nuts. I believe they will be black. Disconnect your two thermostat wires. Using your meter and check from each wire to ground. Connect the red thermostat wire to whichever wire shows 24vAC. The white wire connects to the other black wire. The third wire will be C and connect to the metal frame at any convenient location or screw.

At the stat end you will have red on Rh, white on W1 and ? color on C.


Weil-Mclain EG series wiring
 
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Old 10-05-18, 06:28 PM
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I did as you said and things worked perfectly. The Nest starts up without complaint.

However, when I try to turn on the heat with the Nest, nothing happens. To check that the issue is not my furnace, I switched back to the old Honeywell. Heat turns on just fine with the Honeywell.

Any ideas how to debug this?
 
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Old 10-05-18, 06:39 PM
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To confirm the wires are correct at the nest...... with the nest off the base.....
Check from C to R. You should get 24vAC.
Check from C to W1. You should get 0v.

Finally......
A short between R and W1 should start the heat.
 
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Old 10-07-18, 03:14 PM
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Yep, can confirm all of this is true. Seems like an issue with the Nest itself?
 
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Old 10-07-18, 03:17 PM
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If all that checks out.... it could be a defective base. I've seen quite a few defective ones.
Nest will send you a new one.
 
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Old 10-09-18, 08:14 AM
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Alright, I'll get in touch with them. I appreciate your help!
 
 

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