Nest Thermostat Power Supply and Boiler Problem

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Dmwesq

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I am not even sure I can fully express the issue I am having but I will try. A few days ago one of my 20+ year old zone valves had to be replaced by my plumber. The new valve apparently needs a c wire for the thermostat to work. My older valves did not require a c wire for heat only thermostats - only for heat/cool one. I have two heat only zones which have Nest E thermostats on them. I just had the plumber back in today and he installed a nest Power connector I had purchased, which according to Nest is a viable workaround rather than installing the c wire.

The plumber tested everything before he left, and all my zones were operating properly and supplying heat. A few hours later I come home and have no heat in any zone in the house. The boiler sounds like it is running non-stop, but making some odd sounds I have not heard before, and the display on the boiler is a dark blank screen, so I have no idea what the boiler is doing. Turning the boiler off and then back on made no difference.

So either the power supply is defective, the plumber hooked it up wrong, or somehow it is screwing up the boiler. The boiler is a Burhham K2 and the valve is a Taco Sentry zone valve.

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Fitter30

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Looked at one wiring diagram off the net but take a pic of the boiler diagram probably inside cover. Thermostat connections shows a R W C and c is common. All zone valves have to have power R to W is made in the stat ( R is power call for heat switches to W) and a C wire (common) powers either a little clock motor or a heating element to open valve. The extra wires coming out of zone valve are auxiliary contacts for starting a boiler or pump if used.
 

Dmwesq

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Seems the root of the problem was the wiring diagram in the instructions that came with the power connector were incorrect. Google sent different instructions to me during support call. Their support is horrible and at the same time all of this was going on my Nest Learning Thermostat crapped out and is out of warranty. Moving to Honeywell and never buying a Nest product again.
 

John Gayewski

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You are not the first, but probably the 10 billionth person who has hydronic heat, to also have a problem with nest thermostats. They are not for hydronic heat no matter what they advertise or try to tell you. Don't use nest for boilers steam or hydronic. They just plain aren't compatible.
 

Jadnashua

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Solid-state switches like used in some thermostats will have an upper limit on the VA that can provide. Exceed that limit, and like overloading a fuse, you can burn them out.
 

Dmwesq

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You are not the first, but probably the 10 billionth person who has hydronic heat, to also have a problem with nest thermostats. They are not for hydronic heat no matter what they advertise or try to tell you. Don't use nest for boilers steam or hydronic. They just plain aren't compatible.
My plumber has suggested switching to Honeywell - I assume those are compatible?
 
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