Replacing thermostat. What are all of these wires?


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Old 03-30-13, 03:10 PM
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Replacing thermostat. What are all of these wires?

These are the wires I have coming out of the wall:

White (O)
Blue (W2)
Yellow (Y)
Red (R)
Green (G)
Brown (X)
Orange (E)

I'm going to be installing a Lux TX9100U in a few days. (I like the vacation feature and it was cheap.)

Basically, my question is what are the X and E wires?

I have a Bryant heat pump with Aux heat. I don't know anything about the air handler; I haven't crawled under the house, yet.

About five years ago I replaced the old mercury slider type of thermostat with a RiteTemp programable. I didn't see a place for the X or E wires, so I didn't use them. The touch screen went out the other day, so I replaced it with a Filtrete stat, but my wife doesn't like the way it looks, so I ordered the Lux.

I did notice when I took the RiteTemp off that I had wired it wrong. I had the W2 wire in the W spot and the t-stat set to work in electric mode, instead of heat pump mode. It still worked, though.

Looking at the Lux instructions online it looks like the wiring will go like this:

White (O) --> O
Blue (W2) --> W2
Yellow (Y) --> Y1
Red (R) --> RC (with a jumper to RH)
Green (G) --> G
Brown (X) --> ?
Orange (E) --> ?

Does the Brown X go to C on the stat to power it? (Could I have been saving on batteries all this time?!)

Also, the instructions show a jumper between Y1 and W1? What is that for and is it needed?

Thanks for your help!
 
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Old 03-30-13, 04:18 PM
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Do you have a Q674? ???? number on the old stat?
 
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Old 03-30-13, 04:57 PM
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Do you mean the one I took out five years ago? I don't have it anymore, so I'm not sure exactly which one it was. It was not a Q674, though. It was more like this one.

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Old 03-30-13, 05:42 PM
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I'd remove the panel to the air handler and verify that brown is C since you do not know the model number of the original stat.

The jumper between Y and W is to start the compressor with a demand for heating or cooling.
 
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Old 03-30-13, 06:21 PM
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Thanks for your help, Houston. I'll try to get in the crawl space tomorrow to check out the air handler.

The instructions for the Lux show the Y-W jumper as "customer installed" (as opposed to "factory installed" for the RH-RC jumper.) Is it optional? (I didn't have it on my RiteTemp.) If so, is it better/helpful to have it? What do you mean it starts the compressor with a demand for heating or cooling? Sorry; I don't really understand HVAC systems. Thanks for your patience and willingness to help.
 
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Old 03-30-13, 08:21 PM
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The Y-W jumper is required for heat pump operation with this thermostat.
Without this jumper your heating bill can increase $100 or more per month when using this stat.

Most modern thermostats make this jumper internally when configured for heat pump operation.

I recommend Honeywell 6000 series (or higher) thermostats.
Most pro's will not recommend Lux or Hunter stats.

Setback temps in the heat mode are not recommended with heat pumps since the expensive electric heat strips become energized when the stat tries to reach setpoint after the setback temps expire. (setting the stat more than 1 degree colder when the zone is not occupied would cause the electric heat strips to become energized when the stat tried to warm the home up again)
 
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Old 04-01-13, 10:52 AM
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I was able to crawl under the house, but that didn't help me much. Hopefully someone can make sense of this stuff for me. Here are some pictures.

Also, Houston, you mentioned that you do not recommend Setbacks. How would you recommend handling things like vacations where we are gone for 3+ days? Thanks again for your help.

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Old 04-01-13, 05:33 PM
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I got my Lux in this afternoon and just finished installing it. I just left the X and E wires taped off. The instructions did mention taping off the E wire. I'm still curious about the X, though, so if anyone can make heads or tails of the pics I posted I would greatly appreciate it. Or, at least, take a look at the pics and tell me where and what to look for.

Also, just out of curiosity, I've seen a lot of pros on here saying they don't like the Nest and that there are better wifi/mobile-app-enabled stats for less money. I'm curious what the negatives are for the nest and what you guys would recommend. I have installed two Nests at my church and two other guys from my church have installed them at their homes.

I'm sure a Honeywell or something else would have been better than the Lux, but it was $30 and I figured you can't beat that price for a programable stat!

Thanks so much for your help and feedback.
 
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Old 04-01-13, 09:23 PM
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Your 4th picture shows a small caged area, on the lower left portion of the picture, with the field installed orange wire nuts in it.

If stat brown connects to the air handler brown in the area then connect brown to C at your new stat. (this probably the case).
 
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Old 04-02-13, 12:22 PM
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I crawled back under my house. Still couldn't tell what was what. So, I got out my multimeter. (Duh! I don't know why I didn't think of that first.) Checked the voltage between the brown X and red R. Got ~30V. So, hooked the wire up, popped out a battery, and the stat powered up! I put the battery back in for backup in case of power failure and we are up and running!
 
 

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