Compressor Cord Size?

[bczygan]

I know this has been gone over, but trying to understand.

I have this compressor:
919.165612

It has the following specs:
2 stage
7 Max.developed HP
2.9 Running HP
240V

Because of the 7HP rating everyone recommends hooking up a 50A breaker, #6 Romex and of course hard wiring it.

Specs say a min. 15A branch circuit and time delay fuse.

Two questions.

Is there a special type of breaker required to give the time delay for a motor?

It has #16 wire in it's cord. Why isn't that in danger of overheating? And if hard wiring, should it be changed?

Bill

 

[engineer031]

Ignore the max developed HP it is inflated 2.9 HP so the rating on the motor should read 15 amps. Go with a 20 amp 220 V breaker and 12 g wire
a regular breaker will be fine.
what is the amps on the motor ? 15 ??

 

[bczygan]

Ignore the max developed HP it is inflated 2.9 HP so the rating on the motor should read 15 amps. Go with a 20 amp 220 V breaker and 12 g wire
a regular breaker will be fine.
what is the amps on the motor ? 15 ??

Motor is under a shroud, so can't readily see the markings on the motor itself. But the specs and the plate on the tank both say 15A.

And I have another compressor that will probably replace this one, that has a motor marked 5HP SPL and 15A.

What about the starting load of the motor?

Shouldn't the entire circuit, or at least the breaker be sized for that?

And again, what about the 16AWG wiring on the cord?

Bill

 

[sberry]

The circuit really doesn't need to be sized for start, it is such a short load. Are you sure the cord isn't 14? Is it a factory cord?

 

[bczygan]

The circuit really doesn't need to be sized for start, it is such a short load. Are you sure the cord isn't 14? Is it a factory cord?

From the motor to the switch is 14 and obviously factory.

Bought the unit used and it didn't have a plug on it. From switch out it is 16 and obviously used as it has a taped repair.

I still don't get why the difference between conclusions in discussions about circuit and breaker sizing.

Some experts on here say since this is rated 7HP that you end up with #6 and a 50A breaker by code.

Is that the difference? Code versus what will actually work?

Bill

 

[theoldwizard1]

I have this compressor:
919.165612

It has the following specs:
2 stage
7 Max.developed HP
2.9 Running HP
240V

Because of the 7HP rating everyone recommends hooking up a 50A
breaker, #6 Romex and of course hard wiring it.

WAY OVERKILL ! I'll bet it has a NEMA 6-20 plug, so 12/2 Romex would be fine.

Specs say a min. 15A branch circuit and time delay fuse.

For fuses, yes they do make time-delay.

Is there a special type of breaker required to give the time delay for a motor?

I can't find them in the Square D catalog.

It has #16 wire in it's cord. Why isn't that in danger of overheating? And if hard wiring, should it be changed?

Ridiculous, isn't it ! They can get away with it because the cord is short and the start current lasts less than 1 second.

If you ever have plans to put a longer cord on it, I would use a 12/3.

 

[theoldwizard1]

I still don't get why the difference between conclusions in discussions about circuit and breaker sizing.

Some experts on here say since this is rated 7HP that you end up with #6 and a 50A breaker by code.

Is that the difference? Code versus what will actually work?

No, the difference is actual HORSEPOWER RATING ! I don't understand how these crazy HP ratings come about, but it it runs a 240V@15A circuit, it is likely about 1.5-2.5 "actual" HP.

I have an older Craftsman compressor (oil lubed, 20 gallon tank) with a "real" 2 HP motor. It runs on a 240v@20A fused circuit. The original cord was a 6 foot 14 gauge cord with a 6-20 plug on it. I replaced it with 25 foot 12 gauge cord and have even extended that another 25 foot with an appropriate extension cord. NO PROBLEMS !!

 

[pattenp]

Some experts on here say since this is rated 7HP that you end up with #6 and a 50A breaker by code.

Is that the difference? Code versus what will actually work?

Bill

You are comparing apples to oranges. The motors that are true 7HP are free standing motors and the motor data plate will say 7HP and needs to be wired per the NEC. Your motor on your compressor is not a true 7HP. The running HP is listed as 2.9 HP. Since the manufacturer says 15A min. circuit then that's what you go by. You'll see a lot of corded compressors with just #16 cords. Don't get caught up on the 7HP peak mumbo jumbo.

 

[ron in sc]

Read post #18 in thread cited below.

http://www.garagejournal.com/forum/showthread.php?t=293598&highlight=amps

 

[Strouty]

I would use one about this ( ) size.

 

[bczygan]

OK,
Sounds like both the compressors are like this. The other one says 15A on the motor. So #12 cord would work for either.

Then I'm thinking about future proofing the circuit, for a larger capacity compressor in the future, or a circuit I could use for other purposes.

Bill

 

[sberry]

If everything in it is 14 you would be limited to 30A, a 12 wire 30A breaker would be tailor made for it. Make it work now for this comp, if you really need a bigger circuit someday then fix it. I know the feeling its a human compulsion to want to future proof it all, not worth it. If you do too much of this it becomes a stall and I try to do it less and less all the time.

 

[engineer031]

If it says 15 amp then it is a 3 HP motor go with a 20 amp breaker and wire it for 12 gauge. You can go to a bigger breaker a 20amp and use 12 guage wire because if you use a 15 amp breaker it may trip on heavy use but going to a bigger breaker the unit will only draw what it needs so yes it is ok to use a size up. I would take off the 16 g cord and replace it with a 12 g and you dont need a special breaker.

 

[engineer031]

Some experts on here say since this is rated 7HP that you end up with #6 and a 50A breaker by code
Yes a true 7 HP motor would need a 50 amp breaker but your motor is only 15 amps so it is a 3 HP. It takes 4.5 to 5 amps to make 1 HP at 220 v so a true 7 HP motor will be rated for around 32 amps

 

[bczygan]

I have 2 similar compressors, one oiless and one oiled. Both 2 stage and 220 1PH.

I'd like to know what I can do to hook one up temporarily, because I eventually want to get a true 5HP one so I can run a blast cabinet and everything else. I'll explain the entire setup in a future post as I'm dealing with car problems right now.

Thanks for all the help. I'm seeing that finding out the true HP of the motor is the key element.

 

[wyliesdiesels]

A 5hp is a different ball game.

 

[bczygan]

OK.
I put a 30A plug on the 16AWG cord coming out of the switch.

I'm going to run #12 Romex for the circuit and use a 30A breaker.

 

[bczygan]

Is a true 5HP adequate for things like a blast cabinet?

What is the highest use a home shop might have?

What is a good choice for that?

 

[sberry]

Get rid of the 16 wire if this was not factory installed, Just cause the last guy used it doesn't mean its right. You need to use a 14 or better cord on a 30A breaker. There are cases the 16 could be used on a 20 but the run of this motor is too hi.

 

[engineer031]

OK.
I put a 30A plug on the 16AWG cord coming out of the switch.

I'm going to run #12 Romex for the circuit and use a 30A breaker.

If you are going to use a 30A breaker you will need to run # 10 Wire a # 12 is only good for a 20A breaker, if you have a problem and the breaker is 30 using #12 wire the breaker wont trip and may cause a fire.
Get rid of the #16 coming out of the switch and replace it with min #14

 

[engineer031]

I have 2 similar compressors, one oiless and one oiled. Both 2 stage and 220 1PH.

I'd like to know what I can do to hook one up temporarily, because I eventually want to get a true 5HP one so I can run a blast cabinet and everything else. I'll explain the entire setup in a future post as I'm dealing with car problems right now.

Thanks for all the help. I'm seeing that finding out the true HP of the motor is the key element.

Going to a true 5 HP will require a starter and # 8 wire with a 40 A breaker then it will be dedicated for the compressor only.

 

[engineer031]

Is a true 5HP adequate for things like a blast cabinet?

What is the highest use a home shop might have?

What is a good choice for that?

A true 5 HP 2 stage compressor would be great for a blaster and just about everything else you would use.

 

[engineer031]

I have 2 similar compressors, one oiless and one oiled. Both 2 stage and 220 1PH.

I'd like to know what I can do to hook one up temporarily, because I eventually want to get a true 5HP one so I can run a blast cabinet and everything else. I'll explain the entire setup in a future post as I'm dealing with car problems right now.

Thanks for all the help. I'm seeing that finding out the true HP of the motor is the key element.

If you want it set up so you can use the outlet for other things you can install a 220V outlet and get a plug for the compressor and they you can unplug it and plug something else in but you will need to size your wire and breaker accordingly. 20 amp = #12 wire and 30 amp = #10 wire. And yes you cant go by those compressors that list the HP as peak you need to look at the amps the motor draws

 

[bczygan]

If you want it set up so you can use the outlet for other things you can install a 220V outlet and get a plug for the compressor and they you can unplug it and plug something else in but you will need to size your wire and breaker accordingly. 20 amp = #12 wire and 30 amp = #10 wire. And yes you cant go by those compressors that list the HP as peak you need to look at the amps the motor draws

Thanks!

You guys are getting me edumacated good!

I've got 50' of #10 Romex and a length of #10 SOOW. And a 30A locking plug and receptacle.
This circuit should also work for the small HF welder and rhe Chinese group buy Cut 50F plasma cutter! But, since the plasma cutter needs air, I'll need another circuit. Time for a sub panel.


Bill

 

[engineer031]

now your all set to wire it up....we all need some edumacation !!!