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+-- Thread: What size breaker/wire for a 5hp motor (/showthread.php?tid=7376680)
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RE: What size breaker/wire for a 5hp motor - fredhargis - 09-08-2024
If they used #12 wire to put in the new circuit you have a serious problem. The breaker is meant to protect the wire, which must be sized to handle the load. #12 (or even #10) wouldn't be heavy enough for a 50 amp breaker. Do you know how they wired the 20 amp in?
RE: What size breaker/wire for a 5hp motor - MKepke - 09-09-2024
Fredhargis makes a good point about checking the wire-size used to feed that 20A outlet but…
..regardless if correct wire size was used, a 50A circuit requires 50A receptacles.
-Mark
RE: What size breaker/wire for a 5hp motor - kurt18947 - 09-09-2024
My understanding - and I am not any sort of electrical professional - is that what the machine's manual/specs call for is what's gospel as far as code goes if it's hard wired. I believe 3 H.P. Grizzly table saws were calling for a 40 amp circuit for a while at least. Does a 3 H.P. table saw really require a 40 amp circuit? I certainly wouldn't think so but that's what the manual called for. Would that saw run fine on a 30 amp circuit? In all likelihood, or maybe even on a 20 amp circuit. If the saw were plugged in it could be plugged into a 20 or 30 amp circuit. If it were hard wired it would have to be connected to a 40 amp circuit per the manufacturer. At least that's what I understand.
RE: What size breaker/wire for a 5hp motor - BarryO - 09-11-2024
(09-08-2024, 01:23 PM)fredhargis Wrote: If they used #12 wire to put in the new circuit you have a serious problem. The breaker is meant to protect the wire, which must be sized to handle the load. #12 (or even #10) wouldn't be heavy enough for a 50 amp breaker. Do you know how they wired the 20 amp in?
It's a serious problem no matter what. You can't put a 20A receptacle on a 50A branch circuit. That desk lamp or whatever that could be plugged into the receptacle is expecting to be downstream of a 15A or 20A breaker. When UL or ETL tests the lamp for its listing, it assumes the circuit overcurrent protection is at most 20A.
You often see it written, "the breaker protects the circuit wiring, and not the load", but it's more complicated than that. The NEC is published by the National Fire Protection Association. They want to prevent electrical fires, no matter where they occur. NEC 240.5 describes the overcurrent protection for fixture wires and and flexible cords. It works in conjunction with the allowable receptacle ratings in 210.21.
RE: What size breaker/wire for a 5hp motor - BarryO - 09-11-2024
(09-09-2024, 03:28 PM)kurt18947 Wrote: My understanding - and I am not any sort of electrical professional - is that what the machine's manual/specs call for is what's gospel as far as code goes if it's hard wired. I believe 3 H.P. Grizzly table saws were calling for a 40 amp circuit for a while at least. Does a 3 H.P. table saw really require a 40 amp circuit? I certainly wouldn't think so but that's what the manual called for. Would that saw run fine on a 30 amp circuit? In all likelihood, or maybe even on a 20 amp circuit. If the saw were plugged in it could be plugged into a 20 or 30 amp circuit. If it were hard wired it would have to be connected to a 40 amp circuit per the manufacturer. At least that's what I understand.I have a 3 HP Grizzly jointer and planer. They have Full Load Amp ratings of 16A and 12A, respectively, and came with 20A plugs for installation on a 20A/240V circuit.
I can't see a 5 HP needing a circuit with conductors with more than 30A ampacity. So #10 AWG is fine.
RE: What size breaker/wire for a 5hp motor - Oldwood2409 - 09-12-2024
I just installed a new Jet 5hp band saw. The FLA is 22 amps and the owners manual states that the saw should be on a dedicated 30amp circuit. A 30 amp circuit would need #10 wire from the breaker to the saw (mine does)
RE: What size breaker/wire for a 5hp motor - kurt18947 - 09-14-2024
(09-11-2024, 06:47 PM)BarryO Wrote: I have a 3 HP Grizzly jointer and planer. They have Full Load Amp ratings of 16A and 12A, respectively, and came with 20A plugs for installation on a 20A/240V circuit.
I can't see a 5 HP needing a circuit with conductors with more than 30A ampacity. So #10 AWG is fine.
I have no doubt that 20 amps is perfectly adequate. What I was thinking about is that near the front of some Grizzly machines they specify - or at least used to - the circuit size. So it seems like you could end up with the FLA calling for one circuit size, the front of the manual calling for another. That may not longer be the case, I haven't looked at a Grizzly table saw manual in years. It just stuck with me because it seemed kind of like contradictory information.