It is common for techs to mix up compressor common with capacitor common or transformer common. Be uncommon and don't make these common errors.
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You've seen the c terminal on a dual run: capacitor before you've also seen the c terminal. On a compressor i mean it stands to reason that they would both connect together right. Well, they don't connect together and they're, not even related, at least not in the way that you think in both cases the c denotes a common point in the dual capacitor. It's the common point between the fan capacitor and the compressor capacitor, which is marked as herm in the compressor.
It's the common point between the run and start windings. This is why r plus c, plus s plus c, equals r plus s. If you own a compressor. The c terminal of a dual capacitor is actually fed from the opposite leg of power as the c terminal on the compressor.
This is because you must run power to the start and run windings with the same leg in common with the other leg. A way to remember this is memorizing the same leg that feeds start feeds run and the c terminal on a capacitor is actually the common feeds for the start. Windings of the compressor and fan opposite side from the fan and herm plates on the capacitor, so compressor terminals c goes to one leg of power. R goes to the other.
S goes to the herm terminal on a dual run: capacitor, with the other side of that capacitor c, going to the same leg that feeds r see what i'm saying it's confusing with 208 or 240 volt circuits, the l1 and l2 high voltage incoming lines make no Difference which is which, when you connect, you could swap them on the l1 and l2 on the contactor, and it wouldn't change anything. But once we decide which is connected to run and which is connected to common on the compressor, then we need to hook the run side to capacitor c, not the compressor common side, there's also another common common. We see and that's the secondary side of a low voltage transformer that is opposite from r or hot. You may notice that many low voltage transformers have an ungrounded secondary, meaning that either of the wires in the secondary could be hot or common.
Depending on how you hook it up, and it really wouldn't matter initially, in other words, one side of the transformer is designated hot because we connect it to the line side of our control, switches, thermostat, defrost boards, safety, circuits, etc. It's usually the red wire in common is the common point where all the loads connect together on the opposite side of the circuit, from line and often it's called common or c, if you're new to the trade - and you see the designation c or the words common. Don't assume it's the same as other c and common terminals, even in the same piece of equipment and start connecting stuff together unless you enjoy creating smoke thanks for watching our video, if you enjoyed it and got something out of it, if you wouldn't mind hitting the Thumbs up button to like the video subscribe to the channel and click the notifications bell to be notified. When new videos come out, hvac school is far more than a youtube channel. You can find out more by going to hvacrschool.com, which is our website and hub for all of our content, including tech tips, videos, podcasts and so much more. You can also subscribe to the podcast on any podcast app of your choosing. You can also join our facebook group if you want to weigh in on the conversation yourself thanks again for watching.
Excellent info
Hes always on top of
his game. Great Teacher
I love the graphic illustrations. I screenshot them and keep them in a folder for reference
Probably the most important electrical lesson in hvac ever
buy the book Practical HVAC on AMZN
I had this kick my ass on one of the first compressor change-outs I ever did back in the day, couldn't understand why the brand new scroll wasn't doing anything – after swapping the wires and having it fire up I just kinda stood there confused and then looked at the old wiring diagram and put two and two together….like you said, I assumed 'common was common'.
How about guys wiring in a 3 pole contractor and not check phase rotation.
Good video
After forty years in the trade my head is around what your saying. But it it still sounded like "Whose on first"
If you have no idea what Iam talking about google whose on first.
Iam not being critical i couldn't of explained it any better, and probably not as well.
I just see humour everywhere
We've all had to let tbe Smoke out a time, or two.
It's common sense, duh!
I NEVER had this problem, it never occurred to me until I heard Bryan talk about it. I got over it and won’t listen to this again. I learned from my mistakes!
Oh my gosh the title is a pun!
Wow cant tell you how many times other guys in the shop call me on this ,nd have shown them in the field !!
Gonna send this to them,nd I'm subscribed to your great channel now!
Keep it going ! Your quick explanation on things are so easy to understand, I told them ALLLLL to subscribe 😆 Are you in Orleans ?
See you started speaking slower. Slow, fast, either way always good shit
It helps me to remember the difference is compressor com. is not com. to the capacitor com. Are you in Ottawa ?
when in doubt read the schematic or find it…. Great video!
how about getting using a common wire at the condenser and grounding it to use the original common wire for something else?? I ran into that today while starting up a heat pump but i didnt do it. I requested the company to run new tstat wire but i was really tempted to just ground the condenser board.
That’s pretty common LOL
👍 nice Are you in Kanata ?
This is where schematics come in. If your unsure refer to schematic. Once you hook up the terminals wrong and short the compressor you will never forget. It's all part of the learning process!
Not newer furnaces but in the last 10 years. Some furnaces will run on reverse polarity for a little while.
The transformer does matter because on new furnaces reverse polarity the flame can’t rectification process doesn’t have a big enough ground to rectify the dc voltage.
I’ve always heard the c on a capacitor stood for center. It was called c since it was the center connection on the old oval capacitor.
Great Explanation. Thank you.
Can you recommend an online course to learn HVAC repair?
Am I the only one that keeps wincing whenever they say “high voltage”? High voltage is reserved for 600+ Volts. So a 24V transformer, or a 120V outlet and a 240V capacitor are all common “domestic” voltages. High voltage is reserved meaning you’re going to need special tools, special PPE and in general there will be a fence or a placard designating high voltage as such. It will all carry enough amperage to kill you so treat it as such, you don’t have to say something is “high” voltage because it carries two hot legs. It’s actually lowering the amperage draw on each leg to lessen the load on the motor.
I've started in the trade doing commercial HVAC, so residential seems like it should be easier to understand, but doesn't seem like it to me lol.
Thanks for sharing this video Sir.
Who are the four thumbs down ? They must have misclicked Service area Nepean??
But does it take Glock mags? Service area Orleans??
Over here looking like a blue collar Mr Beast
Don't assume all C terminals are the same and connect things together unless you enjoy creating smoke? I absolutely LOVE creating smoke, every day on the job can be the 4th of July. Just bringing the festivities to our customers. (But first I fill the lines with R290 😁)
I always had to make a cheat sheet for that. Are you in Barrhaven ?
I didn't understand any of that lol
Good video ! So , What happens if u connect the ( L1) to Compressor Common & C on Run cap. Instead of ( L2) to C on capacitor & (L2) to Run. ( Herm to start winding )
I still have trouble finding which terminals are start/run because the plugs are so hard to remove and the comps are way down in the bottom of condensers. Service area Kanata??
What were u just saying there, i didnt get it.
Read the dam destructions
Bro I would love to work alongside you you are like a HVACR fountain
Turns out, common is pretty common! Don't forget about the Com terminal on a spdt switch!
#1!