60 amp breaker with 10 gauge wire???

[thammel]

My 5hp new compressor instructions say 10 gauge wire with a 60 amp breaker...huh?? I ran 8 gauge NM and put in a 40 amp breaker. I can upsize the breaker to60 amps but this doesn't sound correct to me. I thought 6 gauge was required for 50 amps, 8 gauge for 40 amps and probably 4 gauge for 60 amps. Now I can see how the start surge might hit 60 amps, but I'm concerned about having only 8 gauge wire in place.

Comments please!

 

[Terry D]

This is for a motor circuit. Its different. You can oversize the breaker up to 250 percent of the FLA per the table in the NEC. This is for inrush current for starting that motor, so it does not nuisance trip the breaker. It only happens for a milli second. Any short circuit will still trip that breaker. The motor also has internal thermal overloads that will shut it down if it draws to much current for a longer period of time.

If its a true 5hp motor, you will need a # 8 NM-b (romex) or a # 10 THWN/THHN conductor

 

[Bert_]

5hp only pulls ~25A. Needs a big breaker to handle startup current. 40A breaker will probably be fine but is the minimum I would install for a 5hp motor. Code allows up to 70A breaker and #10thhn or #8 romex for 5hp motor.

 

[u2slow]

My 5hp new compressor instructions say 10 gauge wire with a 60 amp breaker...huh?? I ran 8 gauge NM and put in a 40 amp breaker. I can upsize the breaker to60 amps but this doesn't sound correct to me. I thought 6 gauge was required for 50 amps, 8 gauge for 40 amps and probably 4 gauge for 60 amps. Now I can see how the start surge might hit 60 amps, but I'm concerned about having only 8 gauge wire in place.

In a nutshell, motors and welders (inductive loads) break the usual rules of matching breakers to wire sizes.

 

[larry4406]

In a nutshell, motors and welders (inductive loads) break the usual rules of matching breakers to wire sizes.

Not wanting to derail this thread, but I would like to learn more about the rules for welders.

 

[thammel]

Thanks for all your replies! Yes, I have run 8 nmb for this circuit so that should be fine. I'll install a 6am breaker. It is a true 5hp Baldor motor. Check out CAS compressors. Great products!!

 

[MoonRise]

In a nutshell, motors and welders (inductive loads) break the usual rules of matching breakers to wire sizes.

Not wanting to derail this thread, but I would like to learn more about the rules for welders.

Wiring for welders (or some other intermittent and duty-cycle limited devices) are or can be done based on the "Duty Cycle" of the machine.

Since most/many 'home' sized machines (and even some commercial/industrial machines) have a rather limited duty cycle at the high-end output settings, that non-continuous run-time is reflected in the wiring requirements.

made up but semi-realistic example: A welder needs a 50 amp breaker to handle the transformer start-up surge so it doesn't nuisance insta-trip on start-up but only draws maybe 20-30 amps at 'full' output. But it only has a 20% duty cycle at full output. So you might wire it with a 50 amp 240 V double-pole breaker and use #10 wire to the NEMA 6-50R to plug the machine into. (pretty much a buzz-box aka 'tombstone' stick welder)

Code used to require such wiring to be labeled something like "For Welder Use Only" so someone didn't go and plug in something like a 100% duty-cycle 50 amp draw device (heater, perhaps) and thus 'overload' the wiring from the breaker to the receptacle.

 

[sberry]

They dont cause the heater doesnt come with a plug. A buzzer can be 12 single circuit in pipe with 50A. No one thinks thats really great and that is full output which it doesnt normally run so the real draw is about 40 under common use. But, the terminations are poor with that small wire and V drop is rather significant especially at some distance. When a guy goes to 10 most all that goes away.
I think the legal limit on 12 is about 48A.

 

[sberry]

Code allows up to 70A breaker and #10thhn or #8 romex for 5hp motor.

Doesnt it require 8 above 60?

 

[larry4406]

Moonrise - thankyou.

Wiring for welders (or some other intermittent and duty-cycle limited devices) are or can be done based on the "Duty Cycle" of the machine.

Since most/many 'home' sized machines (and even some commercial/industrial machines) have a rather limited duty cycle at the high-end output settings, that non-continuous run-time is reflected in the wiring requirements.

made up but semi-realistic example: A welder needs a 50 amp breaker to handle the transformer start-up surge so it doesn't nuisance insta-trip on start-up but only draws maybe 20-30 amps at 'full' output. But it only has a 20% duty cycle at full output. So you might wire it with a 50 amp 240 V double-pole breaker and use #10 wire to the NEMA 6-50R to plug the machine into. (pretty much a buzz-box aka 'tombstone' stick welder)

Code used to require such wiring to be labeled something like "For Welder Use Only" so someone didn't go and plug in something like a 100% duty-cycle 50 amp draw device (heater, perhaps) and thus 'overload' the wiring from the breaker to the receptacle.

 

[Crazyjake8493]

Not wanting to derail this thread, but I would like to learn more about the rules for welders.

For your reference

 

[wyliesdiesels]

Not wanting to derail this thread, but I would like to learn more about the rules for welders.

https://www.ecmweb.com/national-electrical-code/qa/article/20889547/code-qa

 

[andyvh1959]

I have my welder (Millermatiic MIG) and my compressor (upright 6.5hp) on a 30amp circuit, with the dryer style 30 amp plug connection. Never had any issues on start up or usage for 15 years.

 

[wyliesdiesels]

I have my welder (Millermatiic MIG) and my compressor (upright 6.5hp) on a 30amp circuit, with the dryer style 30 amp plug connection. Never had any issues on start up or usage for 15 years.

a dryer plug (10-30 or 14-30) is not the right plug for 240v equipment. you need a 6-30r and p

 

[u2slow]

Not wanting to derail this thread, but I would like to learn more about the rules for welders.

There's a code section for welders. You will need the line amperage and duty cycle of the machine and do some math.

Or, in your welder's manual, it usually has all this worked out for you... X minimum wire size and Y max breaker size.

 

[Terry D]

I have my welder (Millermatiic MIG) and my compressor (upright 6.5hp) on a 30amp circuit, with the dryer style 30 amp plug connection. Never had any issues on start up or usage for 15 years.

If that compressor is a true 6.5 hp. You should have it hardwired with a disconnect. The proper plug and receptacle for that is very expensive. That dryer plug and receptacle is not rated for 6.5 hp.

Sent from my SM-G960U using The Garage Journal mobile app

 

[sberry]

Remember,,, the min wire and max breaker depends on the wire for the small units. If you use the min wire the breaker is limited, if it's bigger than the min wire the max breaker is 50, the plug it comes with.