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airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 7990
Experience:  Furnace, A/C and heat pump specialist.
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Installing a new thermostat but I have a wire that was

Customer Question

Installing a new thermostat but I have a wire that was attached to letter O on the old thermostat and no where to attach it to the new thermostat.
Submitted: 7 months ago.
Category: HVAC
Expert:  airheatman replied 7 months ago.

What is model on new thermostat? Does it have an O/B terminal?

Customer: replied 7 months ago.
Honeywell Wifi Thermostat.
It does have but this is also where wire labeled W was inserted
Expert:  airheatman replied 7 months ago.

If you can provide me a picture or a list of where each wire went on old thermostat and model of old thermostat,I can help you get this in operation pretty quickly.

Customer: replied 7 months ago.
Here is the old thermostat wiring.
Customer: replied 7 months ago.
Following the installation instructions this is what I've done. But the A/C does not turn on.
Expert:  airheatman replied 7 months ago.

Is your outdoor unit a heat pump? If not sure, give me model number on it

Customer: replied 7 months ago.
I live in a condo. Not sure where the outside unit is. It's probably a cooling tower or something.
Customer: replied 7 months ago.
The inside unit is a Trane serial number W02E22522
Expert:  airheatman replied 7 months ago.

OK lets do this. Wire as follows.

Red to R with a jumper to RC

Green to G

Yellow to Y

White to AUX/E

Blue to O/B

Brown (which was not used ) to C.

Go to indoor unit and connect that brown to common.

The wifi stat is going to require a common wire.

Customer: replied 7 months ago.
I don't have a brown wire
Expert:  airheatman replied 7 months ago.

THat is not a brown wrapped around the bundle? As that just the sheating wrinkled?

Customer: replied 7 months ago.
Did it realize it was a wire. Got it. Ok let me connect the wires.
What do you mean connect to common?
Expert:  airheatman replied 7 months ago.

You will have a C terminal. That is common

Customer: replied 7 months ago.
This is what the inside unit reveals.
Expert:  airheatman replied 7 months ago.

OK what we have to do is find common.

This should be pretty simple to do.

Look at the transformer. It will have 2 high voltage power wires and 2 low voltage wires. The low voltage will go to the board most likely.

The two low voltage wires will be 24v hot and 24v common. One should go to the same terminal Red from thermostat does. The other one will be 24v common. If you can back up about 2 feet and get me a shot of transformer and wires, I might can see it better.

Customer: replied 7 months ago.
Ok. Here are better pictures.
Expert:  airheatman replied 7 months ago.

Excellent.This bue off of transformer is 24v common. Connect that brown from thermostat C to this blue anywhere you can.

Customer: replied 7 months ago.
Ok. Done. Should I try turn it on?
Expert:  airheatman replied 7 months ago.

WE may have to set the thermostat to match the system. Tell me exact model on the wi fi thermostat

Customer: replied 7 months ago.
Honeywell RTH8500WF
Expert:  airheatman replied 7 months ago.

Do you know how to enter system setup menu?

Customer: replied 7 months ago.
Honeywell RTH8500WF1007. From the back of the thermostat
Customer: replied 7 months ago.
Haven't tried.
Expert:  airheatman replied 7 months ago.

Select the following:

0170 - 7

0180- 1

0190- 0

0240- 9

0270- 9

Any other functions are at your discretion.

If any functions listed do not show available, this means thermostat has setup based on a previous selection.

Customer: replied 7 months ago.
Ok. Let me give it a try.
Expert:  airheatman replied 7 months ago.

Standing by

Customer: replied 7 months ago.
I am not getting the thermostat reach out turn on.
Customer: replied 7 months ago.
I not getting the thermostat to turn on.
Expert:  airheatman replied 7 months ago.

Do you happen to have a meter ? Also tell me if COOL comes on thermostat solid or flashing.

Customer: replied 7 months ago.
No meter. The thermostat is off. The display is not coming on.
Expert:  airheatman replied 7 months ago.

Was unit working before you started changing thermostat?

Customer: replied 7 months ago.
Expert:  airheatman replied 7 months ago.

Hmm .Is there a fuse anywhere in the air handler or did you see any spark while messing with wires/

Customer: replied 7 months ago.
None. I had switched off the breakers before I started.
Expert:  airheatman replied 7 months ago.

If you can get a meter I can guide in finding out why we don't have power to thermostat.

Expert:  airheatman replied 7 months ago.

You connected the brown to C on thermostat and blue from transformer right?

Customer: replied 7 months ago.
Don't have meter. Is this something I need to purchase.
Expert:  airheatman replied 7 months ago.

Do this. Remove the R and G wire and touch the wires together and see if blower will come on

Customer: replied 7 months ago.
The blower comes on.
Expert:  airheatman replied 7 months ago.

WE might need to get a meter to make sure there is 24v between the red and blue we are tied into.

Customer: replied 7 months ago.
Ok. So I will need to try this again tomorrow. Can I put the old thermostat back? If yes, do I need to disconnect the brown wire?
Expert:  airheatman replied 7 months ago.

Yes , there is not a C on old so just tape it off.

Customer: replied 7 months ago.
Ok. How do I contact you again tomorrow.?
Expert:  airheatman replied 7 months ago.

I am in and out all day.Just come back to website.

Expert:  airheatman replied 7 months ago.

Make sure we have a meter that shows actual voltage not just a tester that says whether we have voltage or not.

You can get an inexpensive one at Walmart for about 15 bucks if you would like to troubleshoot and I would be happy to guide you.

http://www.walmart.com/ip/Innova-3300-Equus-3300-Hands-free-Digital-Multimeter/14644665

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