What Size Wire For 2 Hp Motor

• #1

Guys - I am a residential electrician. I have a friend that has bought an 80 gallon air compressor. vii.5 horsepower, 240 Five motor, continous duty, fla is listed as 41-43 A. He wants me to run wire for a receptacle for the compressor to plug into instead of difficult wiring it considering he may exist moving it effectually to a dissimilar building depending on usage. The receptacle will but be a few feet from the billow box. I am not experienced in wiring motors of this size and would not take the job except I am trying to help a friend and volition probably simply accuse him for materials. The info with the compressor does not betoken wire size. So, that is my question, what wire size and what size breaker for overcurrent protection? Checking NEC code book it looks like either #10 or # 8 copper and I am not sure what breaker size, 40A or 50A? Any advice?

Location

Tennessee

Occupation

State Electrical Inspector (Retired)

• #2

1st step: Utilise Tabular array 430.248 for your calculations: vii-1/2 hp = xl amps
2d step: 430.22 Branch Circuit: FLA x 1.25 forty 10 ane.25 = 50 amp (normally #8 thhn OR 6 NM)
3rd step: 430.52 BC-GF Protection FLA ten ii.five for IT Billow 100 max
4th step: For string & plug disconnect: 430.109 (F) Plug rated 7.five HP This is probably going to be you stumbling point. A plug and receptacle rated for 7-1/2 HP may exist pricey.

Terminal edited: Nov 11, 2011

• #3

1st stride: Use Table 430.248 for your calculations: 7-1/2 hp = 40 amps
2nd step: 430.22 Branch Excursion: FLA x 1.25 forty x 1.25 = l amp (normally #8 thhn OR half dozen NM)
third step: 430.52 BC-GF Protection FLA ten 2.5 for IT Billow 100 max
4th stride: For cord & plug disconnect: 430.109 (F) Plug rated 7.5 HP This is probably going to be you stumbling point. A plug and receptacle rated for vii-1/2 HP may exist pricey.

Augie, I read this forum daily, and take to commend you on the method in which you answer questions so thoroughly. Leaving nothing out, including code references, takes time and is appreciated!! Thanks.

• #4

Augie - thank you. I was on the right track for the xl x 1.25 = 50A but did not have the 40 x 2.5 for breaker size. Equally far equally the plug and receptacle wouldn't a 40-fifty amp dryer/range - plug/receptacle piece of work?

Location

Tennessee

Occupation

State Electrical Inspector (Retired)

• #5

Augie, I read this forum daily, and take to commend you on the method in which you respond questions so thoroughly. Leaving nothing out, including code references, takes time and is appreciated!! Thanks.

Thank you for your comment...

The time and effrot of others has provided me with the limited knowledge I have. It'southward payback fourth dimension in my life

Location

Tennessee

Occupation

State Electrical Inspector (Retired)

• #6

Augie - cheers. I was on the correct track for the 40 ten ane.25 = 50A but did not accept the 40 x 2.five for breaker size. Equally far as the plug and receptacle wouldn't a 40-50 amp dryer/range - plug/receptacle work?

piece of work ? Near likely
Two inherent problems:
One, if the plug/receptacles aren't properly rated (HP) it is non Lawmaking compliant = liability + possible safety violation
Second: If you lot employ a #8 wire, feed the 60 amp receptacle with a 100 amp breaker, what happens if someone decides to connect a 60 amp load ?

The backgound of most Forumites goes across "what will piece of work"

• #7

Augie - when I asked will information technology work I meant code compliant. I only do residential work and motors are out of my comfort range. Can yous explicate why you can put a 100A billow on #eight wire for a motor? #8 wire is non rated to cary that much current. If you lot ran #8 for an electric stove or any non-inductive type residential load y'all couldn't have OC protection of 100A. Also, would the chapters/structure of a 50A dryer/range plug be any different than one rated for 7.v horsepower? I am not arguing just request?

• #8

Augie - when I asked will it work I meant lawmaking compliant. I only practice residential piece of work and motors are out of my comfort range. Can you explicate why you lot can put a 100A billow on #8 wire for a motor? #8 wire is not rated to cary that much current. If you ran #viii for an electric stove or whatsoever non-inductive type residential load you couldn't accept OC protection of 100A. Also, would the capacity/construction of a 50A dryer/range plug be any different than one rated for 7.5 horsepower? I am non arguing just asking?

The breaker is for brusque circuit and ground protection of the usher only, overload protection for the motor should exist built into the motor already, or needs to be added in a controller.

As far every bit the string goes, it is either rated and listed or non. Most range cords are not listed for HP loads because ranges are mostly resistive and have no real inrush electric current.

• #9

I recollect there is a problem putting a 60A or larger billow on a 50A receptacle. If you hard wire a motor, no trouble putting a larger breaker than the wire size would indicate. Ordinarily, you tin can't practise that for receptacles except for the Welder receptacle exception. He could hope that a 50A breaker allows the compressor to starting time upward subsequently repeated hard use, but a 60A would exist improve. Not sure of the HP rating of a 60A plug/receptacle.

A 7HP 80 gallon compressor doesn't sound very portable to me. Is it on wheels?

• #x

Cheers Jumper. I empathize the HP rating for a motor being unlike than amps for a range. Although, my electrical supply shop tells me they sell no plug/receptacle with a HP rating and couldn't notice any in their catalogues. They are all rated by amps. I get the breaker for the motor circuit is for short excursion/ground fault only and yeah there is OL protection on the motor controls for this motor. So with a 100A billow and #8 wire there would really be no OC protection for the conductors that go from the billow box to the controls? I suppose at that place wouldn't have to be any since about the but fashion you would draw more than 50A current would be a ground fault and the GFCI should take intendance of that or an overload on the motor and the OL protection on the motor would accept care of that?

Location

Tennessee

Occupation

State Electrical Inspector (Retired)

• #11

Thanks Jumper. I understand the HP rating for a motor existence different than amps for a range. Although, my electrical supply store tells me they sell no plug/receptacle with a HP rating and couldn't discover whatsoever in their catalogues. They are all rated by amps. I get the billow for the motor excursion is for short excursion/basis fault only and yes in that location is OL protection on the motor controls for this motor. So with a 100A breaker and #8 wire there would really be no OC protection for the conductors that go from the breaker box to the controls? I suppose in that location wouldn't have to exist any since almost the only way you lot would describe more than 50A current would be a ground error and the GFCI should accept care of that or an overload on the motor and the OL protection on the motor would take care of that?

(modest annotation: may be a "typo" but you stated "GFCI".. there is no need for a GFCI. You may have referenced my SC-GF" for brusque-excursion/basis-error (equally in fault to ground) protection which a standard breaker will provide. Y'all are correct in that the motor OL will prevent overloading.
That's why a receptacle rated greater than the billow presents a problem. Other loads than the motor may non have the inherent OL protection)

• #12

The compressor is not very mobile. He does take it on a sturdy pallet and intends to move it with a fork lift. He owns a trucking business and has employees working on trucks in two different buildings that are close together. Problem is solved, he has decided to let me hard wire it. One of his employees told him it wasn't going to work to motility information technology, too big of a hazard for damage. Cheers for the info guys. I've never paid much attention to the requirements for wiring motors (at to the lowest degree this size of motor) since it doesn't come up much (if at all) in residential work. It helped a lot when you explained the "why" for the requirements.

• #thirteen

The compressor is not very mobile. He does take it on a sturdy pallet and intends to movement it with a fork elevator. He owns a trucking business and has employees working on trucks in two different buildings that are close together. Problem is solved, he has decided to let me difficult wire it. One of his employees told him it wasn't going to work to move it, as well large of a risk for damage. Thank you for the info guys. I've never paid much attention to the requirements for wiring motors (at least this size of motor) since information technology doesn't come up up much (if at all) in residential work. It helped a lot when you explained the "why" for the requirements.

If the buildings are shut together why doesn't he just run an air line between the buildings? Then both volition have air at the aforementioned time. This seems like a large inconvenience to move, and when y'all practice y'all don't have any air at the building it was removed from. Air is usually pretty heavily depended on service in this type of identify.

• #14

Guys - I am a residential electrician. I have a friend that has bought an 80 gallon air compressor. 7.5 horsepower, 240 Five motor, continous duty, fla is listed as 41-43 A. He wants me to run wire for a receptacle for the compressor to plug into instead of hard wiring it because he may exist moving it effectually to a dissimilar edifice depending on usage. The receptacle will only be a few feet from the billow box. I am not experienced in wiring motors of this size and would not take the job except I am trying to help a friend and will probably merely accuse him for materials. The info with the compressor does not point wire size. So, that is my question, what wire size and what size breaker for overcurrent protection? Checking NEC code volume it looks like either #10 or # viii copper and I am not certain what breaker size, 40A or 50A? Any advice?

What Size Wire For 2 Hp Motor,

Source: https://forums.mikeholt.com/threads/wire-size-for-motor.91352/

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