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Is My Thermostat Really Using All 8 of these Wires??

Posted on 10/27/18 at 9:30 am
Posted by Kingpenm3
Xanadu
Member since Aug 2011
8966 posts
Posted on 10/27/18 at 9:30 am
Tying to go smart or wifi with a new thermostat and it doesn't look like any of them can replace what I have. Is it possible that the installer (right at 10 years ago) went ahead and wired both a O and a B here at the thermostat, but only one of them is functioning? Outside unit is a Frigidaire ft4bd-060k heat pump. From a little bit of reading it seems very rare that the system would need BOTH a cooling and heating reversing valve signal. (If that is what I'm finding here) But both the nest online tool and the ecobee support said that they couldn't handle as system with both the O and B wires.



TIA OT Hvac Pros!
Posted by I B Freeman
Member since Oct 2009
27843 posts
Posted on 10/27/18 at 9:39 am to
No HVAC pro but I did buy one of those and I did not have one wire coming from the unit I needed for the thermostat to work. I can’t remember what it is called but I had to call a guy out to run it for me.

Read your instructions and see if you have all the wires coming to the thermostat you need. If you do it is easy to install and I love mine. I put it on my camp so I can check on it.
Posted by Crop Dusting
Member since Apr 2018
166 posts
Posted on 10/27/18 at 9:40 am to
You’re in over your head. Hire a professional
Posted by USAF_Vol
Member since Sep 2005
825 posts
Posted on 10/27/18 at 10:12 am to
I switched to a nest and installed myself. The website gives a wiring diagram. My old one used jumper wires and the nest did not need them.

Check the manufacturer website.
Posted by OysterPoBoy
City of St. George
Member since Jul 2013
35129 posts
Posted on 10/27/18 at 10:13 am to
O is your “on” switch.

B is your “burner”.

So yes, I think you need them both.
Posted by keakar
Member since Jan 2017
30020 posts
Posted on 10/27/18 at 10:37 am to
its been a while so i cant recall them all but.....

red - 24v positive wire to power thermostat
black - 24v negative wire to power thermostat
orange - heat pump solenoid valve
blue - this is normally a 24v negative wire but can also be a 24v positive second stage cooling wire depending on the system
brown - first stage electric backup heater
white - second stage electric backup heater
green - fan motor
yellow - a/c compressor
Posted by Teddy Ruxpin
Member since Oct 2006
39582 posts
Posted on 10/27/18 at 11:11 am to
quote:

No HVAC pro but I did buy one of those and I did not have one wire coming from the unit I needed for the thermostat to work. I can’t remember what it is called but I had to call a guy out to run it for me.


C Wire
Posted by soccerfüt
Location: A Series of Tubes
Member since May 2013
65688 posts
Posted on 10/27/18 at 11:15 am to
quote:

1-8-4-3-6-5-7-2
You already know how to hook them up.
Posted by TheHarahanian
Actually not Harahan as of 6/2023
Member since May 2017
19520 posts
Posted on 10/27/18 at 11:18 am to
Some of those are for the hidden cameras.
Posted by 632627
LA
Member since Dec 2011
12761 posts
Posted on 10/27/18 at 11:29 am to
FYI- if your new thermostat is a nest, please run a c wire or get an adapter.

There are known issues with nests not configured with a c wire.
Posted by RealityTiger
Geismar, LA
Member since Jan 2010
20446 posts
Posted on 10/27/18 at 11:41 am to
quote:

You’re in over your head. Hire a professional

Posted by Spankum
Miss-sippi
Member since Jan 2007
56030 posts
Posted on 10/27/18 at 11:50 am to
There is generally a number for technical help from the manufacturer...I would call that number and they can talk you through this kind of issue pretty easily.
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