farphle
Well-known member
I just inherited a 60 gal compressor (CH VT627505AJ) and need to know what's required to wire it up. Label says 240V/15A/60Hz/1PH. I believe it has a 3.2 HP motor.
Yet another compressor wiring queston
- Thread starter farphle
- Start date
wyliesdiesels
Well-known member
What is the HP rating on the nameplate?
nomadskidoo
Well-known member
Basic volts x amps=watts 240v x15amp=3600watt div by 746 watt per hp=4.825 HP
wyliesdiesels
Well-known member
That calculation doesn't usually work because no motor is 100% efficient.
Also, the nec lists a 3HP motor as having 17a FLC.
So by your math, the NEC would be way off.
wyliesdiesels
Well-known member
Need to know nameplate HP first
wyliesdiesels
Well-known member
Aww yes the typical spl rating.
Id say its about 3HP like the tank says based on the 15 FLA.
So you can use a cord and plug rated for 3HP.
Id say its about 3HP like the tank says based on the 15 FLA.
So you can use a cord and plug rated for 3HP.
sberry
Banned
12 or better wire and a 30 breaker. They will run from a 20 but 30 leaves a bit more headroom for starts. Especially on older units where stuff gets a little worn. As the man said,, you could plug this, use a 6-50,, welder plug/recept.
pattenp
Well-known member
I don't believe you are allowed to oversize the breaker on a cord and plug circuit for motor operated equipment. It will need to be hardwired to use a 30A breaker on #12. Use #10Cu wire with a 30A breaker and a 6-50 outlet & plug. The 6-50 is 3HP rated.
sberry
Banned
Good catch.
It might be legal though as the only other thing that could match it would be welder ? It could be 12/30 for that. could even be 14/30. I would say it definitely not be legal if it was a 30A recept. A 6-30 would definitely need a 10.
It might be legal though as the only other thing that could match it would be welder ? It could be 12/30 for that. could even be 14/30. I would say it definitely not be legal if it was a 30A recept. A 6-30 would definitely need a 10.
alfredeneuman
Well-known member
It's not and never has been.
The only time it's allowed is to use 15A devices on a 20A circuit, but even then using a single 15A receptacle on a 20A circuit is forbidden
pattenp
Well-known member
I'm very well aware of that. I was commenting on the use of a single outlet circuit with an oversized breaker to the wire size for the subject compressor. I should have said you are not to use undersized wire on a motor circuit that uses an outlet.
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alfredeneuman
Well-known member
MountNMan56
Member
20 Amp, 2- pole according to your description
alfredeneuman
Well-known member
You have to go by the NEC tables for both wire and breaker sizes.
3HP is listed @ 17A, which when multiplied by 1.25 (also required) comes out to 21.25A.
So a 20A breaker is undersized for the circuit.
3HP is listed @ 17A, which when multiplied by 1.25 (also required) comes out to 21.25A.
So a 20A breaker is undersized for the circuit.
The 6-50 is required to get the 3HP. However, if using that size P/R, a 50A ckt - (conductors and ocp) must be provided not 30A. NEC 430.42(C) and 210.21(B) govern this since the receptacle does not provide for a dedicated motor ckt. Anyone can plug anything into it.
sberry
Banned
That recept can be fed with a 14 wire and a 30 breaker and a 12 and 50. As was pointed out its not really a motor circuit but welder. It would be legal for this motor with 10 wire I believe.
Also,,, the tag on the comp says 3 up but the motor tag lists spp and includes the draw of 15.
This is really shaving some hairs here,,, its a job for chruler, , ha. But I personally wouldn't lose sleep over a 12/30 which ain't gonna burn the place down. Part of it would depend on what wire I had on hand . Do this for compact welders all the time, its a habit to give these dinky machines all the help they can get.
The receipts are not listed for the minimum wire size anyway and they are usually ran wide open. They lose a little poop specially with longer circuits, the losses really go away with a size up and not sure ALL the brand's are listed for 12,,, I don't recall right now. Seems some are, they all listed for 10 though. If 10 cable is used meets all the listing and v drop for them totally not an issue, same for this comp.
This is really a dedicated circuit, the only other equipment comes factory cord with 6-50 is welders and be legal to use it for depending on the machine,, especially since its limited with a 30.
Anyone can't really plug anything in to it because anything doesn't come with this plug.
Also,,, the tag on the comp says 3 up but the motor tag lists spp and includes the draw of 15.
This is really shaving some hairs here,,, its a job for chruler, , ha. But I personally wouldn't lose sleep over a 12/30 which ain't gonna burn the place down. Part of it would depend on what wire I had on hand . Do this for compact welders all the time, its a habit to give these dinky machines all the help they can get.
The receipts are not listed for the minimum wire size anyway and they are usually ran wide open. They lose a little poop specially with longer circuits, the losses really go away with a size up and not sure ALL the brand's are listed for 12,,, I don't recall right now. Seems some are, they all listed for 10 though. If 10 cable is used meets all the listing and v drop for them totally not an issue, same for this comp.
This is really a dedicated circuit, the only other equipment comes factory cord with 6-50 is welders and be legal to use it for depending on the machine,, especially since its limited with a 30.
Anyone can't really plug anything in to it because anything doesn't come with this plug.
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pattenp
Well-known member
My interpretation is different than yours. 210.21(B)1 for a single receptacle on an individual branch circuit says the receptacle is to have an amp rating not less than the circuit. It does not say the receptacle must be the same amp rating as the circuit nor does it say the receptacle is not to be higher amp rated than the circuit. However 210.21(B)3 does limit receptacles to match the amp rating table where two or more receptacles are attached to a branch circuit.
sberry
Banned
They would certainly need to match the wire size if they are daisy chained. They may be able to have reduced wire if both were to go back to the breaker or to large enough wire that matches breaker.
Example,,, my bud had a recept for welder with 6 or 8. No more spaces in the panel. He gets 2 new machines, had old buzzer. We make the old box a jbox and nut 2 10's to the larger wire for 2 new recepts. Each connected machine is allowed to run at 50, uses 25 max and could use the buzzer singly yet and any overload trips the breaker and the combination will not overheat the main wire.
This make sense? My wording of this situation may not be clear. But its back to the fundamental principle that the applied load and applied loads cannot overheat any part of the circuit.
Example,,, my bud had a recept for welder with 6 or 8. No more spaces in the panel. He gets 2 new machines, had old buzzer. We make the old box a jbox and nut 2 10's to the larger wire for 2 new recepts. Each connected machine is allowed to run at 50, uses 25 max and could use the buzzer singly yet and any overload trips the breaker and the combination will not overheat the main wire.
This make sense? My wording of this situation may not be clear. But its back to the fundamental principle that the applied load and applied loads cannot overheat any part of the circuit.
sberry
Banned
An electric range is wired this way. The only over current protection is the circuit breaker, the only piece of wire thermally protected is the cord and supply circuit and the rest of it is 12 wire internally going to different components, load is calculated for each with wire sufficient for short circuit at 50.
In this case wouldn't you use the amp rating on the motor? The motor plate doesn't claim 3hp. That comes from the marketing material. I'm asking because I don't know. Not an issue for me now but if we move to a new house/build a larger garage it might.
pattenp
Well-known member
Since no HP is listed on the motor data plate (see 430.6(A)(1)) you are to interpolate the HP from the NEC table 430.248. If you interpolate 15A to the table it's less than 3HP, more like a little over 2.5 HP.