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Old 04-13-2010, 04:03 PM   #1
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Difference between 220 and 240 volt requirements?


I'm installing a 30 amp, 240 volt, single phase, stationary air compressor. I've read that this is a confusing issue and in the states they're one and the same in regards to voltage requirements and you can be above or below a voltage requirement for a compressor or other high voltage appliance requirements by 10%.

I plan on using an existing 30 amp breaker in the box formerly used for an electric stove. I also have a 50 amp breaker in the box that is not being used if this would be a better option. Also, after running the wiring near the compressor, I plan on installing a separate box next to the breaker with a slow blow, 30 amp fuse dedicated for just the compressor.

Is a 220 volt and a 240 volt power requirement one and the same and should I use the 30 or the 50 amp breaker?

Any help would be greatly appreciated.

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Old 04-13-2010, 04:11 PM   #2
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Difference between 220 and 240 volt requirements?


Use the name plate of the compressor for the breaker size.

A 30 amp breaker requires #10 wire and a 50 amp breaker requires #6 wire.

240 volt is todays standard, while 220 was used in the past.
They are interchangable.

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Old 04-13-2010, 04:26 PM   #3
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Difference between 220 and 240 volt requirements?


Regional electric companies had slightly different standards, back in the day.

Motors and such are designed to work within the existing range.
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Old 04-13-2010, 07:19 PM   #4
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Difference between 220 and 240 volt requirements?


It was very kind of you to provide such clear and understandable information.

When I see 220 or 240 volts stated now, I'll know more than most and think of you both. Good to know about the regional differences in the past.

jbfan, thanks for the info on the breakers and wire size. Good stuff. Greatly appreciated! I hope this post will help others installing an air compressor.
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Old 04-13-2010, 10:13 PM   #5
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Difference between 220 and 240 volt requirements?


Before we go too much further here, what does the nameplate on the motor state for amps.

If it's 30, a 30 amp breaker won't hold. A 50 might though. If it says in the instructions that it needs a 30 amp circuit, then a 30 is good.

Sizing a circuit for a motor is different than normal wiring. It's one of the few instances where the breaker size can exceed the wire size.

A bit more info would help us a lot.

Rob

P.S. One overcurrent device, be it a circuit breaker or fuses, is enough. More than one is just another possible trouble spot.

A disconnect is required, it must be in sight and not more than 50' away. The breaker in the box is OK if it meets the sight and distance criteria. A cord and plug can serve as a disconnect too.

Last edited by micromind; 04-13-2010 at 10:20 PM. Reason: Added P.S.
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Old 04-14-2010, 07:26 AM   #6
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Difference between 220 and 240 volt requirements?


You folks are truly amazing and I sure appreciate your knowledge and wisdom.

First, the compressor has not been delivered yet so obviously I can't provided you with the info on the name plate. It was supposed to be here three weeks ago.

I have downloaded the pdf manual though. Here is what info I have (I'll copy and paste) from the manual and the site description:

240-volt only motor with manual thermal overload protection

Minimum Branch Circuit Requirement 30 amps

Fuse Type: Time Delay

As previously mentioned, Single Phase, 240V

GROUNDING INSTRUCTIONS
This product should be connected to a metallic, permanent wiring system, of an equipment-grounding terminal or lead on the product.

The supply line should have the same electrical characteristics (voltage, cycle, phase) as the motor. Refer to the motor nameplate, on side of motor, for this information.
NOTE: The wiring must be the same as the motor nameplate voltage plus
or minus 10%. Refer to local codes for recommended wire sizes, correct wire
size, and maximum wire run; undersize wire causes high amp draw and overheating to the motor.

That's all the info I have till delivery. For reference sake it's a Craftsman Professional 80 Gal. Vertical Air Compressor, 5.4 hp. Model # 16781

I'm learning a lot from you and I bet this will help other folks also.

Best regards.
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Old 04-14-2010, 07:31 AM   #7
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Difference between 220 and 240 volt requirements?


I forgot one item that may be of importance.

The distance from the existing breaker box to the location in the garage where the compressor will be installed is approximately 40 feet.
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Old 04-14-2010, 08:24 AM   #8
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Difference between 220 and 240 volt requirements?


Quote:
Originally Posted by cleveland View Post
The distance from the existing breaker box to the location in the garage where the compressor will be installed is approximately 40 feet.
If you're worried about having to upsize your wire for the distance, don't. 40 feet isn't a problem

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