Thermostat Wiring to a Furnace and AC Unit! Color Code, How it Works, Diagram!

In this HVAC Installation Training Video, I show How to Wire the Low Voltage Thermostat Wires into a Furnace and AC Unit. I Explain what each of the Letter Terminals are for, the Voltage Path, How it Works, and also the Normal Color Code Used. I discuss how to Wire the Contactor and what the difference is between the Rc and the R Terminals. Supervision is needed by a licensed HVACR Tech while performing tasks as Experience and Apprenticeship garners Wisdom and Safety.
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⚠️ Disclaimer:
Information in this video is intended for educational purposes only. Any work related to the topics in this video should be performed by licensed technicians or by apprentices under the supervision of licensed technicians. AC Service Tech LLC is not responsible for any possible damages or injuries caused by the use or misuse of any information provided. ▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬
#hvacr #hvacr #hvactrainingvideos #hvactraining #hvactraining101 #acservice #acservicetech #wiring #diagram #wires #furnace #acsystem #thermostat #condenser
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Other tool links can be found in the video description section.

[r.rodriguez]

I looked at your diagram fro 5 seconds and immediately figured out how the last guy wired my whole system wrong. Thank you.

[MrJOSEPHMAMA]

Thank God for a comprehensive and informative video. Some of these channels will drive a guy insane with irrelevant filler.

[tesstee]

Thank you very much for the tutorial. I have been telling my neighbor who bought a new Honeywell RTH2300 thermostate which HAS BATTERYS. I tried telling him you don't need to hook up the blue wire from your furnace to the RTH 2300 thermostat since the thermostat has battery's. I hooked it up this way without the blue wire connected to the RTH 2300 thermostat and BOOM on came the heat. Maybe a gander at this video will convince him.This is the only video I have found that specifically tell's you this about the blue wire and the RTH 2300 Honeywell thermostat. Honeywell done.

[kendogz]

Thank you. I’m an automotive tech but with this wiring diagram and your explanation, I was able to join my furnace and central air from two separate thermostats to one.

[darkwolfe]

Very simple and very detailed explanation! I'm looking to have an AC installed to the existing furnace and now have a better idea how all the components work together.

[donwold]

Thank you for saving my butt, again! Viewed your stuff when a power surge burned up my HVAC circuit board last winter. Used it again today when the AC wouldn't cool (because I left a wire off of the new board). This is AWESOME!

[chesstime]

I don’t know how many times I did watch your videos still I like to watch over and over.

[libertyfox]

Easy to understand. Only one wire "Y" was connected to my compressor, I assumed the other wire went to "C" video confirmed. Issue Resolved on hot day.

[sambrinson]

Got my AC working again, after I replaced the thermostat and some wiring. Thank you so much for the helpful video!

[BGLENN-dptx]

That's the best video explanation of the signal flow for controlling all aspects of the handler and compressor units (and fan). As an electronics designer, I needed this information to complete my wireless performance monitor for my home's A.C. . It will map the efficiency, coolant temps, etc as an indication of declining performance changes BEFORE the compressor eats itself, requiring unnecessary replacement. I will also be buying your book. Based upon your detailed video, I expect the book to provide enough technical information to expand my expertise to do home repairs. Thank you. Great video. As a suggestion, I had to rewind the video a few times at points where message's speed of delivery outpaced my ability to hear and understand it. :-)

[BrettGlass]

Best explanation I've seen, Thanks. I had a new HVAC system installed last year and a honeywell stat that has 4 wire running to it.(no C wire). The system when in A/C mode will set there and run until I turn the stat up, but I have to turn it up 3 or 4 degrees or the temperature reading will jump a degree or 2 to match where I set it to. I know sounds crazy. It will also jump down and match within a degree or 2. SO... first I called honeywell thinking this must be a stat issue. They had me test the voltage readings of the 4 wires running to the stat. The 24v red was fine but one of the wires read lower like 9v and seemed to vary. Honeywell blamed the HVAC system as the problem. So I called the HVAC tech out and after thinking it was the wires running to the stat he checking the voltage readings at the unit with the stat wires removed, he got the same readings ( one circuit was low and varied) eliminating the wires to the stat as the issue. He then said it was an ECM module/motor.He did a warranty replacement of the ECM and said it's fixed. For some reason this issue takes a few hours before it acts up. Then the longer it runs the worse it gets. He finished the warranty repair and said even though the voltage is still low in one circuit the system was working fine, but the next day it did the same thing. I replaced the Honeywell stat again and it does the same thing. I noticed I only have one wire going to the outside unit??? It runs back to the White wire on the inside unit. The other wire that should run outside is hooked up to the Yellow circuit inside and runs to??? in the same harness at the white wire, but never shows up outside. If I unhook the wire not making it outside that is hooked to the Yellow inside wire and then retest voltage at the stat not only does the G wire still show 15.5v but also the Y will now show 15.5 v. Only thing I can think is the return circuit back inside from the outside coil/contactor is being made in the outside unit or through the line set??? This makes no sense.

[dupes_]

Thank you. Replaced my blower motor and knocked some wires loose. Your vid helped troubleshoot.

[tuanden]

This prove that I would literally watch anything that youtube recommend

[joefaulkner]

Saved me in a pinch.replaced my furnace over the winter but didn't connect the condenser lines, thanks a bunch

[nn]

Excellent video explaining what the thermostat does to the wires in different settings. I tested my new thermostat on the bench (with a 24V transformer), verify that in heat mode, the W terminal is ON if setTemp > homeTemp and it goes OFF when setTemp <= homeTemp, but the G wire is still OFF when I set fan to AUTO, G wire only goes ON when fan set to ON. I thought the thermostat is defective but later I verified 3 thermostats behave same way. This video tells me the G wire is only ON when FAN is ON or COOLing is ON. I wish I saw this video before buying the thermostat, save me some grief.
i memorize all these explanations by heart now.

[DLCreations]

Great video helper. Now if just installation techs actually used the color coding correctly, the average home DIYer can fix a broken thermostat without frying something. I have seen and know techs that purposely connect by THEIR standard so when YOU try to fix it, BAM something breaks worse requiring you calling them for more money out your pocket. Since they are "certified HVAC" they will be protected from lawsuit being a non HVAC person should not be touching it in the first place. My 30 year old Nordyne system still runs strong today with my maintenance schedule and compressor cleaning system.

[sunshynff]

Thanks for a simple yet informative description and schematic without talking down to us, I was able to figure out my issue thanks to you, and I had an odd problem too, that I was having trouble finding any info on it.... Blower would come on for the furnace only, AC and manual fan would not work. The condenser and fan on the AC unit kicked on but no blower. It's and old house and I thought I had a light green and dark green wire in my set of six wires from thermostat to HVAC unit. It hit me when watching this video that the dark green wire on my system was actually blue and just faded and dirty. It had come loose when putting in a board the other day, and I thought I messed up, but I hooked it back up and all is working great, thanks again!!

[chuckj]

Thank you. Your video helped me troubleshoot a 24v wire that was shorting to the case ground in my condenser unit. It’s working now!!!

[lesismore]

Just bought a wire toner cuz I confused some wires hooking up a smart thermostat. Hopefully this video will be helpful.