Wiring the A/C disconnect
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- เผยแพร่เมื่อ 24 ม.ค. 2021
- This one covers how to wire the 240 volt, 30 amp disconnect commonly used with split system A/C units. This video is part of the heating and cooling series of training videos made to accompany my websites: www.graycoolingman.com and www.grayfurnaceman.com to pass on what I have learned in many years of service and repair. If you have suggestions or comments they are welcome.
If you are a homeowner looking to repair your own appliance, understand that the voltages can be lethal, the fuels are highly flammable and high pressures are used. Know your limits. - แนวปฏิบัติและการใช้ชีวิต
Line in. Load out. Simple and to the point. Thanks GFM!!
Welcome
GFM
Great and very specific information. As always, well made video
Thank you so much, I really enjoyed the straightforward information.
I have learned when I see it done in a GFM video, I have seen the best way to do it.
Thanks Gray Furnace Man!
Also would point out that line goes to the inside terminals so that when the disconnect is pulled the fuses don't have power. Then you can change the fuses without worry.
Thank you again!
Never not the time to refresh on the basics!
How do you test the fuses? Should your voltmeter be set to ohms? Does it say on the fuse what the ohm reading should be?
With those 2 small individual fuses on a 30amp Central Air Unit. Would you use
2 - 15 amp fuses or 30amp?
30 amp
GFM
I won’t be using it to supply my a/c but instead an outlet for my above ground pool. Should I still get a 30 amp fuse?
Excellent explanation. If there is a white neutral wire coming from the breaker box to the disconnect, where is this connected?
In this disconnect, there is no option for neutral. If there were a provision for a neutral, it would not be switched in the disconnect.
GFM
@@grayfurnaceman do you just clip the neutral short then? My Romex comes with 3 wires and a ground.
@@Rufio6814 Yes.
GFM
Quick question if the plug for the disconnect is burnt on one of the 4 tips does that mean one of the wire is loose or bad terminal ? Do I need to change out the whole disconnect box??
It is probably a loose wire.
In any case, the whole disconnect must be replaced.
GFM
Current code requires connections be torqued down to mfr spec using the proper torque wrench or screwdriver, etc. (approved means). Guess too many people had the wrong idea about tight. 2020 NEC 110.14(D)
In the real world, nobody uses a torque wrench. You know that. Tight means tight.
GFM
@@grayfurnaceman Oh, I understand that. I was just pointing out the language has changed to "shall". Another reason you don't want to get caught out with a loose connection.
Probably stupid question but why is it that a neutral is not needed?
The disconnect is a 240/208 disconnect. There are no 120 volt loads connected to it. If you had a 120 volt circuit on the appliance, you would need a neutral.
GFM
So if you're connecting female power cord with alligator clips to get power for say the vacuum it doesn't matter which terminals you stick the alligator clips on?
It will work both ways, but it is best to use correct polarity.
GFM
Will I be able to send more power back to Edison's grid if I choose a 60amp over a 30amp disconnect?
You don't understand, you pay Edison for power. And whether you use a 60 or 30 amp disconnect makes no difference.
GFM
@@grayfurnacemanSorry I have solar panels and whatever I dont use goes back to the grid
@@Bairov If the wiring is also upgraded, yes
GFM
Lets say I installed the black/white wires coming from the house to the L R posts instead of the LINE posts? (because of some other idiot on TH-cam that I listened to.)
When I turn the breaker on, turn the A/C on at the thermostat, then I hear a poof and the next thing I know my brand new fuses are now toast..
I'm guessing that being wired up wrong is what caused my fuses to blow and not something else ..
Does need a neutral connected from MSP or just a ground?
If the disconnect is for 240 volts only, no neutral is needed.
GFM
How would I wire 110 volts to this?
That is a 240 volt disconnect. It cannot be used for 120 volts. A 120 volt disconnect will have only one pole disconnected.
GFM
Do you know why they are fused?
The NEC requires it lol
It used to be only a requirement that you have a disconnect. Not that it had to be fused. I personally think its not necessary. There is a fused disconnect (breaker) in the panel.
GFM
Why do fuses go out?
Generally, there are 2 reasons for fuses to blow: Excessive amp draw of the circuit, such as a short in the compressor windings.
What seems to be more common, the terminals overheat due to poor connections ie loose connections or a poor connection in the disconnect itself.
GFM
What causes disconnect to blow fuses??????❓
current in excess of the fuse capacity (which should match the circuit cap)
lightning might provide that.
you can get boxes without fuses.
Our disconnect doesn't have fuses.
I might add... those are aluminum lugs, probably should put a dab of noalox on that, especially if its outside.
This disconnect is CU only. Although, noalox would not hurt.
GFM
Thanks for the video. But I hate when an electrician installs a fused disconnect after a properly rated breaker for the equipment im installing. Why? Cause i never have the fuses! And sure as hell he doesn't install them because most disconnects are sold without fuses! I'd rather do everything myself, including the line voltage wiring from panel to a non-fused disconnect.
The use of fused disconnects depends on the codes you are under. A disconnect using a breaker is allowed but most contractors will not use them as they are more expensive.
GFM
Wow I'm over here waiting for u to install the wire and nothing.. I hate videos like this that waist my time..
exactly . another pretentious old timer who fails to educate FULLY . Then way later he finally explains the dumb use of a fused disconnect is due to being a cheap old timer