Thermostat wiring on A/C unit

[jaylectricity]

Normally the HVAC guys that I have worked with will hook up the thermostat wiring if I run it for them. The few times I've done it myself, I've been able to look at the schematic and figure out what goes where. Until today. I'm hooking up an A/C only, compressor outside the residence, air handler in the attic.

The schematic shows all the field wiring then shows the wires that go out to the thermostat and the compressor as a block of wires with a nice handy label: "low voltage field wiring". No symbol representing a thermostat, or a compressor. In fact, it just shows the leads, it doesn't show where they might go.

There is a wire harness in the air handler that contains the leads I can splice to my thermostat wires. A red wire, a blue wire, a green wire, a yellow wire and 3 white wires that terminate on another wire harness. They don't seem to do anything. I ran 18/5 to the thermostat (colors: red, blue, green, yellow, white) and 18-2 (red, white) to the compressor. I haven't connected the thermostat yet but I tied all three reds wires together, then color to color, leaving the white ones alone.

I studied the internal wiring to get an idea of the flow of electricity. Am I going to blow this thing up?

 

[jaylectricity]

Wait, I think I hooked up the white wire to the compressor to the green thermostat wiring, but now I realize the green is the heat. Should it go to the yellow then for the cooling?

 

[ceb58]

I am not sure what you have with this set up. But, I must ask why are you running and/or hooking up the thermostat wireing? If the HVAC guys depended on me doing their job the unit would never run.

Yellow is for cooling. Hooking to ether y or y1 on thermostat

 

[jaylectricity]

I am not sure what you have with this set up. But, I must ask why are you running and/or hooking up the thermostat wireing? If the HVAC guys depended on me doing their job the unit would never run.

I'm getting paid an extra $200 to do it. If I could remember what I did last time I could figure this out.

 

[Buck Parrish]

The HVAC guys are under my own house now. I'll go ask them. It's getting cold in here.

 

[jaylectricity]

I'm googling like crazy. Almost everything is explaining to a homeowner how to replace their thermostat. "Label the wires with the terminals," isn't gonna help me now. :grin:

The informative ones are TOO informative I can't pick out the part that I need.

I want my cake and eat it to.

 

[celtic]

I'm googling like crazy. Almost everything is explaining to a homeowner how to replace their thermostat. "Label the wires with the terminals," isn't gonna help me now. :grin:

The informative ones are TOO informative I can't pick out the part that I need.

I want my cake and eat it to.

Try this
http://highperformancehvac.com/thermostat-wiring-colors.html


...I like pie :grin:

 

[Buck Parrish]

They didn't know.
On an other note how long should a warranty on a new furnace be. I had one installed 18 months a go. So far they have been back 6 times to do different things to it. It has an electrical diagnosis light and it is blinking three times.

 

[jaylectricity]

Try this
http://highperformancehvac.com/thermostat-wiring-colors.html


...I like pie :grin:

Ooooh...I like that one. Looks like the reason there were a bunch of white wires doing nothing is because there is no heat associated with this setup.

Thanks...I actually prefer brownies.

 

[celtic]

On an other note how long should a warranty on a new furnace be. I had one installed 18 months a go. So far they have been back 6 times to do different things to it. It has an electrical diagnosis light and it is blinking three times.

On someone else's work?
Every time they comeback, the clock starts again.


On my work?
As soon as my break lights are out of sight.

:grin:

 

[jaylectricity]

So far they have been back 6 times to do different things to it.

Yeah, I want to avoid a call-back...this job is a 40 minute highway drive. And that's at 6:45PM. You don't want to know how long it takes during rush hour.

 

[Buck Parrish]

On someone else's work?
Every time they comeback, the clock starts again.


On my work?
As soon as my break lights are out of sight.

:grin:

It's their own install, I have called themback six times. Once the main blower was shot. I think we got a lemon.

 

[Buck Parrish]

It was spider crickets stuck in my heat condensation line. Causeing water to back up, closing the float switch.

 

[danickstr]

so now I guess those vinyl hoses going to the outside should be covered with a mesh or something. there never used to be condensate lines on the old furnaces of my childhood...I wonder why.

 

[celtic]

Thanks...I actually prefer brownies.

That's great...but YOU owe ME.


DO will ship
:grin:

 

[Buck Parrish]

Yes, I have saw 20 year old furnaces in crawl spaces running like heck with never having a problem. Now the new ones have so many sensitvity devices, they will shut down for the smallest thing.

 

[electricmanscott]

In a cooling only setup you only need two wires to the condensor and two or three to the thermostat. I can't say which ones or which way to connect them without seeing the setup.

On a side note. Why do guys around here let the HVAC guys do this wiring?

Aren't we the electricians? Don't we do wiring?

I hear this from guys all the time. Both electricians and HVAC guys. I don't get it. I always do all of the wiring on an HVAC system.

 

[mtfallsmikey]

so now I guess those vinyl hoses going to the outside should be covered with a mesh or something. there never used to be condensate lines on the old furnaces of my childhood...I wonder why.

High efficiency gas furnaces are condensing..meaning the heat exchanger extracts so much heat from combustion that the flue gas condenses...has to drain somewhere...heat exchangers have to be mfd. from stainless.

 

[mtfallsmikey]

In a cooling only setup you only need two wires to the condensor and two or three to the thermostat. I can't say which ones or which way to connect them without seeing the setup.

On a side note. Why do guys around here let the HVAC guys do this wiring?

Aren't we the electricians? Don't we do wiring?

I hear this from guys all the time. Both electricians and HVAC guys. I don't get it. I always do all of the wiring on an HVAC system.

You are correct. color does not matter, but in A.C. only......Y at the t-stat,or relay goes to the compressor, R (RC for cooling)is hot, RH is heat (isolated at the sub-base to prevent any bucking) W is common, B is common, but used in heat pump rev. valves, G is fan.

Never had any electrician do my control wiring....

 

[growler]

Aren't we the electricians? Don't we do wiring?

I hear this from guys all the time. Both electricians and HVAC guys. I don't get it. I always do all of the wiring on an HVAC system.

Why, we don't sell HVAC systems and we sure as heck don't want to warranty them so why get involved.

Supply power to compressor and air handler and then it's theirs, they get paid for the install.