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Combine my AC and heating thermostats with a remote sensor? how to wire?

Combine my AC and heating thermostats with a remote sensor? how to wire?


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Old 05-17-14, 07:26 PM
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Combine my AC and heating thermostats with a remote sensor? how to wire?

I've got a very basic analog thermostat on the second floor for my central air conditioning system. On the first floor I've got a cheap digital thermostat that controls the heat. Both thermostats only have two wires going into them. I picked up some 18/5 from home depot and am going to rewire and upgrade the central air thermostat.

At the same time I'm thinking of combining both thermostats. I'm thinking of installing a Honeywell TH8110U1003 Vision Pro 8000 on the first floor, and a Honeywell C7189U1005 White Indoor Remote Temperature Sensor on the second floor. Is that the best way to do it? I figure I can emphasize the upstairs temp during summer, the downstairs temp during winter or just average them.

Also not having done this before, I'm having a little trouble wrapping my head around how I'm wiring the this to the condenser and the boiler. Is it one 18/5 going to the boiler where I'll connect a "pair" of the wires (and a third, new common?), then continuing to the condenser where I'll connect the "other pair" of wires (as well a new common)?

Thanks
 
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Old 05-17-14, 08:07 PM
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You would be running (at minimum) an 18-5 cable between the thermostat and the A/C air handler. You would use Rc, Y and C from the air handler. Then you could use a piece of two wire from there to the boiler to pick up those two wires which will connect to Rh and W.

The A/C unit would be supplying the power to run the t'stat.
 
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Old 05-17-14, 08:21 PM
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Thanks, great info. This may be slightly the wrong section but if I wanted to add a overflow shutoff switch on my secondary AC drain pan I could splice it into the Y wire right then and there correct?
 
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Old 05-17-14, 08:28 PM
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Normally you would splice the overflow safety switch between the Y terminal at the air handler and the Y wire to the compressor unit. If the pan overfilled.... the compressor would shut off but the blower will continue to run.
 
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Old 05-18-14, 05:33 AM
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Cool, thanks. I only have 18/5 wire, but I'm thinking of running a spare 18/5 at the same time in case I ever need more wires.
 
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Old 05-18-14, 08:56 PM
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It never hurts to run more conductors than you need.
 
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Old 05-20-14, 04:43 AM
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Looks like I was mistaken on how the remote sensor works. I didn't realize after hooking it up, it disabled the thermostat's internal sensor completely.

Does anyone have recommendations on either keeping two separate thermostats (one upstairs for ac one, one downstairs for heat) OR a single thermostat on the first floor where I just program in different temps based on day/night/etc (i.e. a couple degrees colder at night)?

Is there a preferred method (2 separate vs 1 thermostat)?

Thanks
 
 

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