Residential HVAC wiring.

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SomeRandomPerson

SomeRandomPerson

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Location
Massachusetts
Occupation
Electrician
I was wondering if anyone has a good reference or book suggestion on residential hvac wiring? I’m not very knowledgeable on the subject and would like to learn a bit more. Sometimes I’m called upon to help our HVAC department like I was this afternoon.


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Hv&Lv said:
You mean like the thermostat wiring or the 240 to the units themselves??
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Oh that would help. My mistake. I’m looking mite for the low voltage side. I was sent to a home that for some reason had two separate t stat in both floors. One for heat, one for AC. The home owner wanted to just have one ecobee upstairs and one downstairs. It didn’t go very well


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SomeRandomPerson said:
Oh that would help. My mistake. I’m looking mite for the low voltage side. I was sent to a home that for some reason had two separate t stat in both floors. One for heat, one for AC. The home owner wanted to just have one ecobee upstairs and one downstairs. It didn’t go very well


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Many thermostats can be wired to do that. The ones where you can do that have an Rh and Rc terminal. Those are for the power from the control power transformers in the equipment. Rh is the power for the heat, and Rc is the power for the AC.
 
Check out YouTube, there's tons of really good hvac guys posting incredibly good content
 
SomeRandomPerson said:
I was sent to a home that for some reason had two separate t stat in both floors. One for heat, one for AC.
Click to expand...
That comes from independent systems installed at different times.

Years ago, when I was a helper, the boss wired separate heating and cooling systems through a pair of single-pole switches in a 2-gang box, with one of them mounted upside-down. He drilled the toggles and joined them with a long 6-32 screw and nuts, and labeled the switch positions "heat" and "cool."
 
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The color assignments, by the way, are based on how cables themselves are made, like the way we can use white for hot in NM and other cables when necessary, and evolved as HVAC systems did.

Originally, heating control was 2-wire, so red and white was used. When forced-air systems arrived, red became the "hot" and the green that 3-wire came with was assigned to the fan, yellow in 4-wire for A/C, etc.
 
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