I recently bought a pair of Saylor Beall 80 gallon vertical tank compressors, the seller said the motors were 5 hp 3 phase. Turns out they are 5 hp single phase I bought the compressors not running and now need to verify the motors work. Can I direct wire to my shop panel just to verify they run? I plan to use mag starters when I put the compressors back together.
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5hp electric motor without a magnetic starter
- Thread starter plout99
- Start date
joe_padavano
Well-known member
Just be aware that a 5HP single phase motor will draw just under 30 amps. Be sure the wire and outlet are rated for that.
wyliesdiesels
Well-known member
should be less than that. most 5HP motor nameplates list around 23a FLA. The NEC FLC tables state 27a for 5HP but that isnt what they draw.Just be aware that a 5HP single phase motor will draw just under 30 amps. Be sure the wire and outlet are rated for that.
It ultimately needs to be hard-wired unless pin & sleeve recept/plug is used. All hardware must be HP rated - not amperage. Max NEMA devices are 3.5 hp.Just be aware that a 5HP single phase motor will draw just under 30 amps. Be sure the wire and outlet are rated for that.
The compressors will be hard wired this is just to bench test the electric motors. I do not know if they work or not. I was planning to replace them since I was told they were 3 phase and found out when I was pulling the motors and pumps off the tanks to make loading the compressors easier they are single phase.
nadogail
Well-known member
Just because we can make something work, despite the NEC Code, dosent mean we should go ahead and do it.
joe_padavano
Well-known member
Still not a 20A outlet...should be less than that. most 5HP motor nameplates list around 23a FLA. The NEC FLC tables state 27a for 5HP but that isnt what they draw.
pancho400cid
Well-known member
With the compressor unloaded (discharging through an open valve or whatever), but connected to the motor with the belt, the motor will be accelerating the compressor parts to speed until it gets to full speed, and then it will run at whatever current/power the friction, windage and minimal compression work takes. It will be a lot less than full load amps, but still could be a bit much for your shop breaker.
Pulling the belt off and running just the motor alone would draw quite a bit less power than above, and the motor would be at full speed almost instantly reducing the chance of tripping your breaker.
The connection info posted above is true for long term, but if you just want to see the motor run at no load, you can get by with a temporary wiring set up - but you should have a breaker in your test set up.
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Pulling the belt off and running just the motor alone would draw quite a bit less power than above, and the motor would be at full speed almost instantly reducing the chance of tripping your breaker.
The connection info posted above is true for long term, but if you just want to see the motor run at no load, you can get by with a temporary wiring set up - but you should have a breaker in your test set up.
...
wyliesdiesels
Well-known member
did you mean receptacle? a disconnect is considered a power outlet as well.Still not a 20A outlet...
regardless, it shouldnt be connected to a receptacle at all.... unless its pin and sleeve style. nema receptacles are max 3.5HP
Like you said, "most". I have a 5HP 27 amp motor on my compressor so they exist. Heavily loaded it will pull 27 amps. NEC is going to error to the safe side.should be less than that. most 5HP motor nameplates list around 23a FLA. The NEC FLC tables state 27a for 5HP but that isnt what they draw.
wyliesdiesels
Well-known member
The FLA on the nameplate is listed at 27a?Like you said, "most". I have a 5HP 27 amp motor on my compressor so they exist. Heavily loaded it will pull 27 amps. NEC is going to error to the safe side.
Yes.The FLA on the nameplate is listed at 27a?
CGT80
Well-known member
My 5hp baldor (213t 1-3/8" shaft 109 lbs weight) motor is 28.5 amps, at 208-230v, on the name plate, then add in the 1.15 service factor. It only lists one amperage for the voltage range. Motors have become more efficient over the years and the newer ones pull less current. Last I checked, it pulled 27 amps when it got up to 170 psi on a Westinghouse air brake company compressor, running just over the 800 rpm the pump is rated to at 5hp. Voltage is normally 244 here and I have seen 169 amps flash on my greenlee clamp meter, per leg.
For testing or temporary usage, Nema 6-50 plug and receptacle and 10ga sj cord will work. Of course, I let the pressure switch do the work and didn't plug it in or unplug it while running. It may have run on 10ga romex and 6-50 setup, tied to a 30 amp breaker for a while, but the user may have had plenty of experience running electrical and kept a close eye on it. Now, it is wired into a 50 amp breaker with #6 wire and a magnetic starter setup.
Code is what is best and what is legal and safe. What works in the real world is what people can get away with. It works until it doesn't.
For testing, I wouldn't sweat the details, but for permanent use don't risk it and just make it to code.
For testing or temporary usage, Nema 6-50 plug and receptacle and 10ga sj cord will work. Of course, I let the pressure switch do the work and didn't plug it in or unplug it while running. It may have run on 10ga romex and 6-50 setup, tied to a 30 amp breaker for a while, but the user may have had plenty of experience running electrical and kept a close eye on it. Now, it is wired into a 50 amp breaker with #6 wire and a magnetic starter setup.
Code is what is best and what is legal and safe. What works in the real world is what people can get away with. It works until it doesn't.
For testing, I wouldn't sweat the details, but for permanent use don't risk it and just make it to code.
justsam
Well-known member
I have an IR 60 gal. vertical compressor that has been in my hobby level shop for over 15 years. Probably gets used 3 to 4 days a week. It has a 5 HP Baldor motor controlled directly by a Sq D pressure switch. Never had a failure. Yes it is hardwired to a 30 Amp 240VAC circuit. I don't dispute the use of mag starters but it is certainly not an NEC requirement, and more modern motors, (lower amperage) and better contact materials make the use of direct pressure switches a reliable system with fewer points of failure.
As long as the motor has some acceptable means of overload protection, a starter is not required. There are many 5HP rated pressure switches used in the power circuit vs. control circuits.I have an IR 60 gal. vertical compressor that has been in my hobby level shop for over 15 years. Probably gets used 3 to 4 days a week. It has a 5 HP Baldor motor controlled directly by a Sq D pressure switch. Never had a failure. Yes it is hardwired to a 30 Amp 240VAC circuit. I don't dispute the use of mag starters but it is certainly not an NEC requirement, and more modern motors, (lower amperage) and better contact materials make the use of direct pressure switches a reliable system with fewer points of failure.
wyliesdiesels
Well-known member
As long as the pressure switch is rated for the HP and as said above the motor has overload protection…I have an IR 60 gal. vertical compressor that has been in my hobby level shop for over 15 years. Probably gets used 3 to 4 days a week. It has a 5 HP Baldor motor controlled directly by a Sq D pressure switch. Never had a failure. Yes it is hardwired to a 30 Amp 240VAC circuit. I don't dispute the use of mag starters but it is certainly not an NEC requirement, and more modern motors, (lower amperage) and better contact materials make the use of direct pressure switches a reliable system with fewer points of failure.