75hp motor supply

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Toros

Senior Member
Location
Tujunga, CA
Hi
I need to figure out the wire size & ocpd for of supply feed to 75 hp, 208 v motorized, pressure wash boot in an indust. place
(feeder runhing through 75 degreee invironment, indoor, regular temparture)

Per the book: 75 hp @ 208v is 211 FLA


Can I use 4/0 thhn @ 90 deg. or
should I use 300mcm @ 75deg. ??????

Thank you
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
While you have the book out, take a look at 110.14.
You will find that in 99% of the situations, you can only use the 90? rating for de-rating purposes and the final amperage can not exceed the 60 or 75? ratings accordingly.
In you case you need the 300kcmil.
If this washer is actually a piece of equipment where there may be associated loads, you might check the manufacturer's naneplate currents prior to installing wire.
 

kwired

Electron manager
Location
NE Nebraska
While you have the book out, take a look at 110.14.
You will find that in 99% of the situations, you can only use the 90? rating for de-rating purposes and the final amperage can not exceed the 60 or 75? ratings accordingly.
In you case you need the 300kcmil.
If this washer is actually a piece of equipment where there may be associated loads, you might check the manufacturer's naneplate currents prior to installing wire.


Even without considering 110.14 you will still have 75 deg terminals on overcurrent devices, disconnecting means, motor controllers, etc in almost all instances.
 

iwire

Moderator
Staff member
Location
Massachusetts
Even without considering 110.14 you will still have 75 deg terminals on overcurrent devices, disconnecting means, motor controllers, etc in almost all instances.

:?

If we don't consider 110.14 the terminal ratings are meaningless. :huh:
 

kwired

Electron manager
Location
NE Nebraska
:?

If we don't consider 110.14 the terminal ratings are meaningless. :huh:
110.3(B) would be next step to determine temp ratings, but yes 110.14 is more direct and to the point and covers anything that doesn't have listing or instructions
 

kwired

Electron manager
Location
NE Nebraska
Good point. Kind of an expensive way to connect a 75 HP motor. Guess he has no other option available.

75 hp is still small enough it may make sense in some instances if 480 volts isn't readily available - or if there is just the one larger load and everything else will be desirable to run at 208/120.
 
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