Ideal 240V Outlet Mounting Height?

[DC73]

Putting two 240V circuits in the new workshop. One for a planned new vertical air compressor (probably 5 HP but no larger). The other for a future welder.

Is there an ideal mounting height for the outlets?

Thanks much,

DC

 

[Trey T]

Where will the compressor be located in relation to the outlet?

 

[pattenp]

The 240V outlet you will most likely being using for the compressor is only rated up to 3HP. A true 5HP motor should be hardwired.

 

[canbug]

High enough you don't have to bend over to plug in or be hidden behind that box you put on the counter. Yes, you can get the appropriate receptacle that is HP rated.

Tim.

 

[DC73]

Where will the compressor be located in relation to the outlet?

Compressor will be against the back wall in a corner right next to the outlet/box which will be on the side wall (left side).

The 240V outlet you will most likely being using for the compressor is only rated up to 3HP. A true 5HP motor should be hardwired.

Thanks. What height would you recommend the box be installed? I'll hard wire if needed. But, why hard wired? Is it code or just best practice? Why wouldn't an outlet work?

High enough you don't have to bend over to plug in or be hidden behind that box you put on the counter. Yes, you can get the appropriate receptacle that is HP rated. Tim.

Is there a specific model number outlet that would work for a 5HP compressor? I have an extra 4-wire 30 amp dryer outlet. Would that work?

Thanks for the help.

DC

 

[pattenp]

It's a code and UL thing.

http://forums.mikeholt.com/showthread.php?t=164752

http://www.cooperindustries.com/con.../arktite-60a-plugs-receptacles-connectors.pdf

Mount the box at an easy access height. It would be good to use an A/C disconnect if a disconnecting means is not in sight of the compressor.

*

 

[Trey T]

Compressor will be against the back wall in a corner right next to the outlet/box which will be on the side wall (left side).


...

DC

five feet off the ground to the left of the compressor. It makes it easy for disconnect.

I feel like this will be another thread with many NEC-huggers.

 

[wyliesdiesels]

High enough you don't have to bend over to plug in or be hidden behind that box you put on the counter. Yes, you can get the appropriate receptacle that is HP rated.

Tim.

sure u can. IF u want to sell your arm and leg.

All joking aside the only receptacles that are rated for more than 3HP(Standard NEMA outlets are rated 3HP), are the expensive pin and sleeve connectors...

five feet off the ground to the left of the compressor. It makes it easy for disconnect.

I feel like this will be another thread with many NEC-huggers.

NEC huggers? Do it right or dont do it at all! Theres so much hack work out there its unbelievable!

 

[DC73]

It's a code and UL thing.

http://forums.mikeholt.com/showthread.php?t=164752

http://www.cooperindustries.com/con.../arktite-60a-plugs-receptacles-connectors.pdf

Mount the box at an easy access height. It would be good to use an A/C disconnect if a disconnecting means is not in sight of the compressor.

*

Thank you, that info makes the reasoning clear. The breaker panel is within 3 steps of the proposed compressor location but I do like the idea of an AC disconnect at the compressor location.

What about the welder outlet? Any hard wire or specific outlet requirements for it? I have not picked out a welder yet. In fact, I've never welded but have always wanted to learn and so I am planning for a future acquisition.

DC

five feet off the ground to the left of the compressor. It makes it easy for disconnect.

Thanks Trey. 5' would definitely work for my application. I actually have a range from about 18" to 5' or so that would work well but wasn't sure whether it would work best to be higher or lower within that range.

DC

 

[sberry]

Thank you, that info makes the reasoning clear. The breaker panel is within 3 steps of the proposed compressor location but I do like the idea of an AC disconnect at the compressor location.

It doesn't get any better than you got. Why add more junky equipment in the middle of a perfectly good wire.
The welders all use the same plug, 6-50-P and a 10 wire or better. Buy a piece of 8, use part for a comp and part for a welder.

 

[larry4406]

I mounted my compressor outlet at about 48" above floor. I used a 50A range receptical and range cord on the compressor. No disconnect.

I don't plan on unplugging the unit while it is running as the mike holt link alludes.

Cheap, looks clean, and works fine for me.

YMMV.

 

[DC73]

It doesn't get any better than you got. Why add more junky equipment in the middle of a perfectly good wire.
The welders all use the same plug, 6-50-P and a 10 wire or better. Buy a piece of 8, use part for a comp and part for a welder.

Thanks for the input. I've already acquired some #8 THHN for both circuits. Is there an optimal height for the welder outlet?

I mounted my compressor outlet at about 48" above floor. I used a 50A range receptical and range cord on the compressor. No disconnect.

I don't plan on unplugging the unit while it is running as the mike holt link alludes.

Cheap, looks clean, and works fine for me.

YMMV.

This was my original plan. I don't plan on unplugging it either but I also don't have a problem with hard wiring it.

DC

 

[rsanter]

Anywhere between elbow and shoulder height

Bob

 

[Trey T]

...NEC huggers? Do it right or dont do it at all! Theres so much hack work out there its unbelievable!

What's not right about the OP's setup? Is it simply because it's not a 5HP-rated plug/receptacle? So here's my question: for an induction motor (5HP, 3600rpm or 1800rpm) using plug/receptacle (30A), where's the biggest risk (fire or injury) during operation of the motor?

Keep in mind, the OP isn't trying to get a permit or approval from the local authority; he's the installer and operator of the plug/receptacle.

 

[zkling]

What about the welder outlet? Any hard wire or specific outlet requirements for it? I have not picked out a welder yet. In fact, I've never welded but have always wanted to learn and so I am planning for a future acquisition.

You are going to want a Nema 6-50R on a 40amp or 50amp breaker with appropriate size wire for the run. Mount it ~36" off the floor and make sure the grounding pin is at the top to get the plug/cord going in the down direction. The large majority of welders and plasma units, if 240V capable, will come with a ~6' long 10ga cord with a molded on 6-50P installed to the machine.

 

[rockwithjason]

What's not right about the OP's setup? Is it simply because it's not a 5HP-rated plug/receptacle? So here's my question: for an induction motor (5HP, 3600rpm or 1800rpm) using plug/receptacle (30A), where's the biggest risk (fire or injury) during operation of the motor?

Keep in mind, the OP isn't trying to get a permit or approval from the local authority; he's the installer and operator of the plug/receptacle.

the biggest risk is in two areas, during starting and during a disconnection. starting current can be many times the rating of the plug, that is why plugs come with a hp rating. it makes it easy to know which plugs are up to what motor loads. the second is disconnection and the reason is obvious.

as for the inspection thing, i wonder if you would feel the same about the crank in your avatar meaning that somebody made it "good enough". the reason so many people do hack work is that they can't physically see what is happening in the circuit so if they don't see a problem it doesn't exist to them. that in no way reduces the danger.

 

[Trey T]

the biggest risk is in two areas, during starting and during a disconnection. starting current can be many times the rating of the plug, that is why plugs come with a hp rating. it makes it easy to know which plugs are up to what motor loads. the second is disconnection and the reason is obvious.

as for the inspection thing, i wonder if you would feel the same about the crank in your avatar meaning that somebody made it "good enough". the reason so many people do hack work is that they can't physically see what is happening in the circuit so if they don't see a problem it doesn't exist to them. that in no way reduces the danger.

There's only one risk, when plug/unplug the starting/running motor and we have all experience that many times in our lives with electrical devices in our home. When it's plugged in, there's no reason why there would be a risk while it operates normally because the ampacity of the plug/receptacle is properly sized (see specs in my previous post and review NEC if necessary).

I typed and deleted most of my message about fundamental of installation (NEC), equipment, and operation (OSHA); how those three can affect the safety of human and their possession. I'll just leave with these questions:

Why would you want to disconnect it while it's running? Similarly, if it's hardwired, why would you want to disconnect that while the compressor is running?

 

[rockwithjason]

Dude if you want to be a hack then have at it. The man asked the question and we answered. Game over.

 

[DC73]

Just to be clear, I have a permit. I'm in the rough-in stage at the moment and hope to get a preliminary inspection later this week or next. Final inspection will come before I choose a compressor or welder so I will install a blank cover over the two 240V boxes until I'm ready.

I was more interested in getting opinions on ideal mounting heights and I learned something about the need to hard wire or provide special plugs/receptacles for larger compressors.

Thanks to all who helped.

DC

 

[Charles (in GA)]

Why would you want to disconnect it while it's running? Similarly, if it's hardwired, why would you want to disconnect that while the compressor is running?

You go in the house to eat lunch. You come back out to find the compressor running, and running, and running, only to discover it has pumped way above the max pressure and hasn't shut off. You panic and pull the plug (because its there, and the breaker panel is on the other side of the shop, or another area altogether) and get a huge flash and arc when you do. Turns out the magnetic starter jammed or welded closed and neither the pressure switch nor the thermal overload switch breaking the coil circuit does any good.

Charles

 

[George-V]

You go in the house to eat lunch. You come back out to find the compressor running, and running, and running, only to discover it has pumped way above the max pressure and hasn't shut off. You panic and pull the plug (because its there, and the breaker panel is on the other side of the shop, or another area altogether) and get a huge flash and arc when you do. Turns out the magnetic starter jammed or welded closed and neither the pressure switch nor the thermal overload switch breaking the coil circuit does any good.

Charles

Very good scenario.

 

[Dick in Wisconsin]

You go in the house to eat lunch. You come back out to find the compressor running, and running, and running, only to discover it has pumped way above the max pressure and hasn't shut off. You panic and pull the plug (because its there, and the breaker panel is on the other side of the shop, or another area altogether) and get a huge flash and arc when you do. Turns out the magnetic starter jammed or welded closed and neither the pressure switch nor the thermal overload switch breaking the coil circuit does any good. Charles

Very good bad situation scenario.

 

[slodat]

I like my receptacles in the shop to be 54" floor to bottom of the four square. It's high enough a sheet of plywood laying on the long edge can lean under it.