Sizing circuit for air compressor motor

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Dsg319

Dsg319

Senior Member
Location
West Virginia
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Wv Master “lectrician”
Got an 50amp outlet (existing) been using it for a air compressor. I’ve got number #8 AWG conductors and gonna put back 40amp OCPD.

motor specs. FLA-15amps 3-HP(FLC-17amps). 240volt single phase. Motorhas built in overload.

17FLC x 250% inverse time brkr =42.5ampere permitted OCPD.

Reason being I’m using almost full 250%percent is to keep the 40ampere OCPD with #8s because it will still very rarely be used for an old tombstone Lincoln welder.(hence the 50amp plug). Spec for welder says input 50amp. But have used it thin metal low settings for sometime without many nuisance trips.

Seem okay?
 
hbiss said:
As long as the motor has built-in overload and is cord and plug connected it looks OK to me.

-Hal
Click to expand...
Motor does have built in overload and does have oversized(50)amp cord and plug hooked up to it, to utilize same outlet as the welder.
 
Did the "17 amps" you mention come from the actual motor nameplate or you using the Table ?
(Reason I ask is some "3 HP (advertised)" compressors are not actually 3 hp motors.)
 
I had an old tombstone Lincoln for years on a 20 amp 240 breaker.
Never tripped with all the rods I burnt with that unit.
It only needs that high amperage if you are blowing through steel on the highest setting it has.
 
Hv&Lv said:
I had an old tombstone Lincoln for years on a 20 amp 240 breaker.
Never tripped with all the rods I burnt with that unit.
It only needs that high amperage if you are blowing through steel on the highest setting it has.
Click to expand...
I just made a thread regarding this welder.
 
augie47 said:
Did the "17 amps" you mention come from the actual motor nameplate or you using the Table ?
(Reason I ask is some "3 HP (advertised)" compressors are not actually 3 hp motors.)
Click to expand...
17 amps The table. Nameplate amps was 15. Single phase
 
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