Compressor Wiring and Amps

[Kyngfish]

Hi all. Just took delivery on a 2 stage 5 hp compressor from puma. the 5040 model. The motor label says voltage is 208-230V and 22-25 amps. I currently have a wire set aside for it that goes to a breaker that is 2 20 amp breakers delivering 115 V each.

The wiring diagram in the manual that came with the compressor (not the motor) is asking for a 40-60 amp breaker. My understanding of those ratings is that they are for EACH breaker, so basically what that says to me is they are asking for 80-120 amps across two breakers, which seems like a lot. I don't know if this is a generic wiring diagram for multiple versions of the same compressor, which can come with much higher HP, but it feels like a ton.

Just hoping to see if someone can help me clarify....

 

[brewchief]

A two pole breaker( these can look like two separate breakers with the handles connected) is rated at total amps, you don't add the two together. If it says 20 amps its 20 total.

What type and size is the wire that is existing?

Where in relation to the panel is the compressor going to be located?

Does the motor nameplate list it as 5hp or does it say SPL in the horsepower spot?

Motors with a horsepower number listed are required to be wired with the wire sized by a table in the NEC.( if your not in the USA this may change). The breaker is sized differently for motors as well and can be a lot higher then what most people expect for a given wire size.

Sent from my SM-G965U using Tapatalk

 

[wyliesdiesels]

No thats not what that means.

Lets go over the basics for motor circuit wiring.

NEC table 430.248 lists 5HP as 28a FLC. Wire is sized at 1.25. 28*1.25 = 35a

So a 5HP motor will need 35a rated wire- #8/2 NM-b or #10 THWN in pipe.

The motor will need to be hardwired as standard nema outlets are not rated for more than about 3HP.

This brings us to the breaker sizing

Breakers can be sized max 250% of FLC- 70a for 5HP.

You wont need a breaker that high though. A 30a or 40a should work. The 20a breaker will definitely NOT work.

Now as far as breaker ratings go, you dont add up both sides of the breaker. A 40a double breaker is a 40a 240v double pole breaker.

So what size wire do you currently have?

Theres a few other things you need to keep in mind.

A local disconnect is required if the motor is more than 50’ from, and not within sight of, the panel.

 

[Kyngfish]

No thats not what that means.

Lets go over the basics for motor circuit wiring.

NEC table 430.248 lists 5HP as 28a FLC. Wire is sized at 1.25. 28*1.25 = 35a

So a 5HP motor will need 35a rated wire- #8/2 NM-b or #10 THWN in pipe.

The motor will need to be hardwired as standard nema outlets are not rated for more than about 3HP.

This brings us to the breaker sizing

Breakers can be sized max 250% of FLC- 70a for 5HP.

You wont need a breaker that high though. A 30a or 40a should work. The 20a breaker will definitely NOT work.

Now as far as breaker ratings go, you dont add up both sides of the breaker. A 40a double breaker is a 40a 240v double pole breaker.

So what size wire do you currently have?

Theres a few other things you need to keep in mind.

A local disconnect is required if the motor is more than 50’ from, and not within sight of, the panel.

Thanks for the detailed feedback. The wire is running about 5 feet from the panel. There's a plug there now, but I can just hard wire from the junction box. It is ten gauge wire in metal.

My board does have some space amp-wise - so is it just as simple as swapping that double 20 to a double 30 and call it a day? (Confirming i have ten gauge wire at running at close proximity to the panel and the panel has amp headroom)

 

[u2slow]

Wylie pointed out the NEC rules require bigger wire for those motor specs.

The reality is, that 22A@240V motor will be just fine on #10 wire.

I would use a 30A 2-pole breaker either way.