Factory air compressor wire size

[dm9289]

We have a compressor name plate 293 amps.
Definitely a continuous load in our case should wire size be based on 293 x 1.15 =336 amps

Or the 200hp motor compressor 240amps x1.15 + the remaining 53 amps= 329


Or am I off on completely

 

[dm9289]

Please forgive the error for top part I meant
293x1.25=366

Or 200hp at 240x1.25 +53=353

Or 240x1.25 +53x1.15=361

 

[retirede]

Do you end up with a different wire size for any of those values?

 

[augie47]

A 200 HP by NEC would be 240 X 1.25 = 300 amps
Is it just the one motor ?

 

[don_resqcapt19]

There has to be either a special type of motor or more than a single motor for the equipment. I would base everything on 125% of nameplate.

 

[dm9289]

A 200 HP by NEC would be 240 X 1.25 = 300 amps
Is it just the one motor ?

No the unit has a cooling fan and various electronics

 

[dm9289]

There has to be either a special type of motor or more than a single motor for the equipment. I would base everything on 125% of nameplate.

Yes more than motor largest 200hp

 

[dm9289]

Do you end up with a different wire size for any of those values?

In copper not for 2 of 3 but the 329 could use smaller wire

 

[retirede]

In copper not for 2 of 3 but the 329 could use smaller wire

I was only looking at the numbers in post #2. You have to use the compressor nameplate, not just the main motor.

 

[dm9289]

I was only looking at the numbers in post #2. You have to use the compressor nameplate, not just the main motor.

Yes main air compressor nameplate is 293A

 

[electrofelon]

There has to be either a special type of motor or more than a single motor for the equipment. I would base everything on 125% of nameplate.

I was only looking at the numbers in post #2. You have to use the compressor nameplate, not just the main motor.

Something I've never been quite clear on, when do we use motor data and when do we use name plate data?

 

[LarryFine]

Something I've never been quite clear on, when do we use motor data and when do we use name plate data?

Aren't they the same thing? I would ask when to use motor nameplate vs code tables.

Nameplate for overload, tables for circuit.

 

[electrofelon]

Aren't they the same thing? I would ask when to use motor nameplate vs code tables.

Nameplate for overload, tables for circuit.

What I mean is, when do I use machine nameplate vs NEC horsepower to full load current table. Something like a package HVAC unit we use nameplate of course per article 440, but consider something not covered by 440, say like a table saw or compressor like the OP has? Do we just ue the nameplate data and use the motor data if it doesnt have one? What f the nameplate doesnt match the NEC method?

 

[retirede]

What I mean is, when do I use machine nameplate vs NEC horsepower to full load current table. Something like a package HVAC unit we use nameplate of course per article 440, but consider something not covered by 440, say like a table saw or compressor like the OP has? Do we just ue the nameplate data and use the motor data if it doesnt have one? What f the nameplate doesnt match the NEC method?

Very good question. Here’s how I view it (not saying I’m right):

If equipment contains multiple motors, or motors and other loads, use the equipment nameplate.

If the equipment has only one motor, or a motor that is most of the load (like 90% or so), use the worse case between using the equipment nameplate or the NEC tables for the motor.

 

[LarryFine]

I think I answered that correctly:

Nameplate for overload, tables for circuit.

 

[topgone]

I would like to make a dab on your sizing.
Conductors should be sized 125% of the full load amps of the circuit. If the full load amps = 240A, choose a conductor capable of carrying 240*1.25 = 300A (350MCM, good for 310Aat 167deg F).
Overloads have a built-in 115% factor into the setting dial, that is if the current limit you want is 293, you dial in "293" amps. Don't worry about the TOR tripping under 293A as the TOR will trip at 1.15% x 293 = 335.8A.

 

[retirede]

The branch circuit must be sized based on the compressor package nameplate amps. The overloads must be sized based on the nameplate amps of each motor.

 

[infinity]

The branch circuit must be sized based on the compressor package nameplate amps.

I agree, for a package unit that contains more than just a single motor the nameplate is used to size the circuit. Continuous load gets sized at 125%, non-continuous can be sized at 100%.