I just purchased a compressor with a 15amp 240 v motor.
I have 2 separate 110v circuits close to the compressor.
Can I use the hot leg from each of these circuits to supply 220v?
Logically it sounds correct, but I am not an electrician.
Thanks,
Bob
Hi Bob,
First, I would never want to give advise that might harm or KILL somebody. Electricity is something that you cannot take lightly or it will do just that. With that said I will give you my opinion what I think you should do. You really need to supply your air compressor with 220vac form you breaker box with the recomended 220 volt breaker. This type breaker will work properly if something should happen where the two seperate breakers might not and could cause some damage or personal harm. You never want to take shortcuts or chances when it comes to electricity. Also depending on the distance you have to run the wire you will need at least a number 10 AWG maybe 8 AWG size copper wire or comprable size aluminum wire (the smaller the number the larger the wire). You more than likly have 12 or 14 AWG at your recepticles and that would be too small anyway and would get very hot and could cause damage. If I were you I would consult a local electrician and have him give you a hand or at least show you the SAFEST and best way to take care of your need.
I hope this has helped and I hope that I did not step on your toes with my response... I just think that the safe way is always the best way.
Rok,
Thanks for the info..
I have done quite a bit of electrical work in the past, but this was a new situation, and I was trying to use what was available...
I will run a new circuit for the compressor,(It will be a PITA)..
Thanks
Bob
Good move running the 220 volt line because even if this can be made to work I can see several possible issues here, especially if you manage to trip just one breaker and not the other which I think might happen.
You are required by the NEC (National Electrical Code) to run a circuit from a two pole circuit breaker that serves only that motor load. You will run then, two hots and a ground. Depending on your local codes, this can be in NMC, MC or raceway AKA flex or pipe.
Depending on the circuit length, this might be in #10 or #8 depending on the distance and RLA, running load amps. THe back of the NEC has tables for calculating voltage drop, but I'm sure there are on-line calculators for you to figure this out.
DO NO SKIMP ON THE WIRE SIZE. This will cause a fire.
Also I believe aluminum wire (mentioned above) is no longer is accepted by code. be sure to use copper. 15 amps is not much but the distance you are pushing it is important in determining the guage. You would deff. want to use a dedicated 2 pole circuit.
have fun, keep it safe
There is nothing prohibiting one from using aluminum wire but it doesn't make sense for the do-it-yourselfer due to engineering and installation issues. HD, Lowes and other home centers usually only sell copper wire in the smaller sizes anyway.
You are required by the NEC (National Electrical Code) to run a circuit from a two pole circuit breaker that serves only that motor load. You will run then, two hots and a ground. Depending on your local codes, this can be in NMC, MC or raceway AKA flex or pipe.
Depending on the circuit length, this might be in #10 or #8 depending on the distance and RLA, running load amps. THe back of the NEC has tables for calculating voltage drop, but I'm sure there are on-line calculators for you to figure this out.
DO NO SKIMP ON THE WIRE SIZE. This will cause a fire.
How can you determine if you have the circuit wired correctly? For 115v you can simply plug in a circuit tester and it will tell if the polarity and grounding is correct. Is there any such device for 230v? If not then how can you check?
Any good voltage tester or volt meter will do, as long as it is fairly accurate and can read 300 volts.
A 230 volt outlet in a residence most commonly will have three holes. One will be radically different from the other two and will be the ground. The other two will read 220 volts between them and 115 volts to ground.
The outlet size and configuration will depend on the load you are putting on it and the duty, ie you can get a light residential type outlet all the way to pin and sleeve types for industrial use.
Note that you don't necessarily need an outlet as many things can be direct wired and direct wiring is desirable with motor loads on equipment that remains stationary like air compressors and welders at a work station.
Just L1, L2 and the ground are sufficient. These will be the wires from a two pole breaker and the ground bus in the panel. If you are running romex, you will have a black white and bare wire. Relabel the white wire with red tape, it will be a hot not a ground in your circuit. If you run EMT or other raceway, pull a black, red and green in the pipe.
Just L1, L2 and the ground are sufficient. These will be the wires from a two pole breaker and the ground bus in the panel. If you are running romex, you will have a black white and bare wire. Relabel the white wire with red tape, it will be a hot not a ground in your circuit. If you run EMT or other raceway, pull a black, red and green in the pipe.
bluesman2333....that's what I thought........thanks
Another question: I am running a line from the current dryer 240V outlet out to the garage. The dryer outlet is on a separate line and has a subpanel with two 20V breakers just above the outlet. The line to the garage is going to be basically an extension and not hardwired into the circuit. I will unplug the dryer and plug in the extension line. The dryer circuit is on 12 gage wire (or at least it should be). Since the extension line to the garage is about 55 feet, should I run 10 gage or stick with 12 gage?
Also, there should be no difference in wiring for a dryer other than it may have a neutral wire included........correct?
Just L1, L2 and the ground are sufficient. These will be the wires from a two pole breaker and the ground bus in the panel. If you are running romex, you will have a black white and bare wire. Relabel the white wire with red tape, it will be a hot not a ground in your circuit. If you run EMT or other raceway, pull a black, red and green in the pipe.
The circuit breaker size is only loosely associated with the load. The wire size for a motor load starting a compressor could be heavier than a #10 for a 30 amp circuit. #10 might be fine for a dryer but you might need #8 or possibly #6 depending on the distance and the load, ie if the compressor starts hard.
A good rule of thumb is to take 125% of the running amps then look at what circuit breakers would be suitable, at 80%. So, a 20 amp compressor would be 25 amps for calculation sake and a 30 amp breaker would be 24 amps so a 40 amp breaker with a minimum of #8 would be used.
The dryer circuit is on 12 gage wire (or at least it should be).
Also, there should be no difference in wiring for a dryer other than it may have a neutral wire included........correct?
Yes.......you are right.......the dryer circuit is 10 ga wire with a 30 amp double pole breaker. Using 10-2 w/ground wire ............does the neutral pin on the plug get wired to the ground?
Yes.......you are right.......the dryer circuit is 10 ga wire with a 30 amp double pole breaker. Using 10-2 w/ground wire ............does the neutral pin on the plug get wired to the ground?
No it does not. In the case of a dryer using 10-2 wire, a neutral is not used.
Where 10-2 wire was used (old code) the receptacle and plug should be 3 prongs. In new installations (10-3 wire) a 4 prong receptacle and plug are used. You shouldn't install a 4 prong receptacle when 10-2 wire is used. (It would work, but it's the wrong thing to do.)
If you have a 3 prong receptacle and a 4 prong plug on a new dryer, your dryer cord should be changed to a matching 3 prong plug. Your big box hardware stores will carry the cords.
No it does not. In the case of a dryer using 10-2 wire, a neutral is not used.
Where 10-2 wire was used (old code) the receptacle and plug should be 3 prongs. In new installations (10-3 wire) a 4 prong receptacle and plug are used. You shouldn't install a 4 prong receptacle when 10-2 wire is used. (It would work, but it's the wrong thing to do.)
If you have a 3 prong receptacle and a 4 prong plug on a new dryer, your dryer cord should be changed to a matching 3 prong plug. Your big box hardware stores will carry the cords.
The outlet I installed in the garage is a 3-prong, 50A, 250V (6-50R). The directions say the third pin is ground. I wired this pin to the neutral wire and it seems to work fine.
In a residential install, the neutral will be ground. You need to tape it green and re-land it to the ground bus if there is one. With this outlet, you need to run a minimum of #8, so the dryer circuit wiring will be too light if that's what you used.
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