I have Weil-McLain gas boiler for hot water heat and going to install WiFi thermostat that requires common 24V 'C' wire. I do have a free wire in the cable but cannot figure out where should I connect it on the boiler, there's no any terminal, marked as 'C', 'common' or similar. The system includes hot water boiler and central AC. Currently I use thermostat with battaries that has 5 wires going in.
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Just a heads up that there's been a suggestion to make a generic question about how to locate the C wire terminal on the HVAC/Boiler the encompass many similar questions. If you'd like to rephrase this question to be more generic, we can use this rather than considering it a dup once the other question is created.– BMitchCommented Nov 7, 2013 at 21:11
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This answer might be helpful.– Tester101Commented Nov 8, 2013 at 0:42
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1 Answer
According to the CGa-010 wiring diagram, you'll want to connect the C wire for the thermostat to the terminal pointed to in this image.
Notice the transformer is circled in red. The location where the transformer wiring terminates is circled in orange. The "common" side of the transformers secondary is pointed to by a large blue arrow.
answered Nov 8, 2013 at 1:12
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Thanks a lot, I locate the wire, but didn't connect it yet.– DmitriyCommented Nov 12, 2013 at 18:29
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Is there any difference what transformer use for C in two-transformers system? I have independent boiler and A/C. I'm going to use boiler transformer to power termostat, but doubt if it could influence A/C.– DmitriyCommented Nov 12, 2013 at 18:32
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You'll use the same transformer that supplies the
Rwire to the thermostat. Commented Nov 12, 2013 at 18:33 -
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You'll pair the
Cfrom the boiler, with theRfrom the boiler. Commented Nov 12, 2013 at 20:16