Nest looses power when calling for heat

[SBK1]

I have a hot water "boiler" supplying radiators with heat.

I used a "c" wire from my aqua-stat to the Nest. The Nest has the W and the R wire also connected - power from a separate transformer. Why do I loose WiFi and get power messages when the thermostat turns on?

[AlexD]

Thanks for reaching out to us here @SBK1 . I would be happy to try and assist. Would you be able to take a picture of the thermostat base, so we can have a clear view on how it is wired? 

[SBK1]

I connected a C wire I was told to take from the aqua-stat to the C terminal on the Nest and the other 2 wires to the same terminals as my old thermostat. R & W . @Houptee below suggested do not use the C from another source. So I will be trying that.  there are two schematics I am considering. 1 from page 11 of the pro installation and another from this forum

[SBK1]

Hi @AlexD .and @Houptee 

So this is the typical schematic on the Honewell sen set up .

Boiler has no C.  the Aqua-stat powers the Zone Valves (RED Wires). I have the Transformer that is powering the T stats Yellow wires

for the NEST:

I have 1 thermostat which has 4 wires R , W, and 2 spares. So how do I get the Correct "C" connection to it

In the other case only 2 wires to the thermostat - must be spliced in the wall somewhere.  So in this case I have to use the Nest power module. How do I do this? and Do I remove the bridge in the Adapter?

thx

[Houptee]

You have wiring reversed at Tstat. Red is + goes to R then White is the output to the system so it goes to YW current flows thru the valve motor out to YC the common side and returns to the transformer C common terminal to complete the circuit.

The just run a C wire to the C on the tstat and you will have power all the time to the Nest.

See my attached drawing.

[SBK1]

Hi there @Houptee.  It worked.

I had to disconnect both the original wires to the zone valve. Then follow your diag o e wire connection at a time..

The original R to the T stat should be erased from the diag. But I figured I couldn't have 2 Rs so disconnecting all makde it simple. 

Thanks again 

[AlexD]

It is great to hear @Houptee suggestion worked. Has the thermostat been behaving as expected since then? 

[Vladut]

Hi there, just checking in with you. Do you still need help?

[Houptee]

This is the wiring for the one that needs the Power Adapter.

[SBK1]

thanks @Houptee 

Ill follow it and post once done - probably after Christmas .

A question though.... Do I remove the bridge inside the power connector of leave it in place?

I guess I try both way. But thought I'd ask.

Happy Holidays

[Houptee]

No do not remove the cap that is only removed if you have to add an external transformer, you have a transformer in the circuit so you leave the cap in place.

[SBK1]

Thanks. I'll update once installed. 

[Vladut]

Thank you so much @Houptee!

@SBK1 Can you please keep us in the loop and let us know once you've tried the suggested steps?

[Vladut]

Thank you so much for all the input everyone!

@SBK1 Can you please send me a picture of the base?

[Houptee]

You cannot have the C wire coming from a different transformer as the R wire.

R is + and C is - they have to come from the same source transformer.

Try to find the transformer that the Red wire gets its power from and connect the C wire to the common side of that transformer (there are 2 wires that leave the 24v transformer, one is going to your Red so the other wire will be common).

Some boilers that have older relay controls do not have a easy way to get to the common, such as Honeywell switching relays.

There is a common on every transformer.

Post pics of where on the boiler the R and W connect now and we can help you figure out how to attach the C wire.

[SBK1]

All resolved via the help of the individuals in the community ( not Google). I'd have expected Google to take the lead but didn't

[AlexD]

Thank you for your feedback. We and all the users are always happy to assist. While we can certainly add our input that does not mean other users can't come up with great ideas or suggestions before us. 

Thanks again @Houptee for the assistance provided. I will go ahead and close this thread. If anything else comes up, feel free to open a new one.