Air Compressor electrical connection

[sti491]

Hi all.

I have a new Quincy 5-HP 80-Gallon Two-Stage QT Pro Air Compressor (230 Volt 1-Phase), model 251CP80VCB.

I am placing it within 4 feet of my 200 amp breaker box. The manual is pretty skimpy on specifics to hook it up, other than where to attach the wires and that it needs a 60 amp breaker.

I am planning to add a 60 amp breaker to the box (there are only a few circuits on this box now, just lights and some outlets), then wire it correctly to the compressor per the manual instructions, after cutting all power to the box of course.

What wire size do I need to connect it to the 60 amp breaker? It's very close to the breaker box.

 

[sberry]

You don't need a 60, that is the max. an 8 wire and a 50.

 

[sti491]

It specs a 60 amp breaker. Still use 8 with that?

 

[pcmeiners]

I use 40amp breakers, motor draws 22amp @120psi.

 

[fsae0607]

Compressor wiring rule of thumb is:

Wire Size ==> (Motor Plate Full Load Amps) X 1.25

Breaker Size ==> (Motor Plate Full Load Amps) X 2.50

 

[sberry]

That is the max allowable. Yes, 8 can be used on some types of circuits to 100A. This comp needs 10 in pipe or 8 in cable. For 10 wire the max is 60. There are a quite a few 5 hp running for decades with 30, I have one on it. While larger breakers are allowed I would rather have it closer. There is no reason to use one bigger than 40 unless there is a reason to use a larger one, trips at starts etc. I have a 3 hp on a 30, it ran for decades from it, all of a sudden trip,,, something wrong with the unit and inmop it was a good thing.

 

[rlitman]

That is the max allowable. Yes, 8 can be used on some types of circuits to 100A. This comp needs 10 in pipe or 8 in cable. For 10 wire the max is 60. There are a quite a few 5 hp running for decades with 30, I have one on it. While larger breakers are allowed I would rather have it closer. There is no reason to use one bigger than 40 unless there is a reason to use a larger one, trips at starts etc. I have a 3 hp on a 30, it ran for decades from it, all of a sudden trip,,, something wrong with the unit and inmop it was a good thing.

I'm with you. My 7.5HP compressor happens to be on a 30A breaker. It's been that way for almost 10 years now, though it is on 6AWG wire. I just happened to have the 30A 2-pole breaker handy, and since it never tripped, I never changed it.

On that note, I had a day where an air line burst, leaving the compressor running continuously for a few hours before I could get someone to shut it off. The breaker still did not trip. This unit happens to be rated for continuous duty, and has a starter box with overload protection, so if it didn't trip then, I'm not all that worried.

 

[stonesfan68]

It specs a 60 amp breaker. Still use 8 with that?

I'd still check their math. That sounds like a really big breaker for a 5HP 230/1 motor. For comparison, I'm using a 30-amp breaker and 10 AWG wire for my 5HP compressor. I don't know the motor full,load current (FLC) offhand, but I sized it according to the IR specifications given in the manual at the time.

Also, NEC Table 430.248 specifies the FLC of single phase motors. The 5HP 230/1 motor FLC is 28 amps. The data table is what is supposed to be used for wire sizing.

 

[Trey T]

for 60A, no smaller than 8g.

btw, the leads to the motor is only 10g stranded copper for Baldor 1800rpm I've seen, if not all 5hp. So if you're making a 1ft connection from your motor/starter to the breaker w/ a 8g, it is absurd. I don't want to get into a debate over this but think about it.

 

[CNGsaves]

Compressor wiring rule of thumb is:

Wire Size ==> (Motor Plate Full Load Amps) X 1.25

Breaker Size ==> (Motor Plate Full Load Amps) X 2.50

^ ^ General . . "rule of thumb" . . yes . . . . BUT
. .
. . .
. . . .
GJ Sparky's have taught us countless times that . . . HP RATING
. . . . yes . . do NOT look at FLA on motor plate
. . (unless no other way like with "SPCL" or special listing for HP)
. .
and use HORSEPOWER to determine Wire Size and Breaker on larger DIRECT-WIRED compressors.

 

[sberry]

I think the "special " may actually allow it to run from a 10 cable 30 breaker.

 

[fsae0607]

^ ^ General . . "rule of thumb" . . yes . . . . BUT
. .
. . .
. . . .
GJ Sparky's have taught us countless times that . . . HP RATING
. . . . yes . . do NOT look at FLA on motor plate
. . (unless no other way like with "SPCL" or special listing for HP)
. .
and use HORSEPOWER to determine Wire Size and Breaker on larger DIRECT-WIRED compressors.

I'd be more inclined to use HP ratings on a Baldor or Leeson since they're US-made and have true ratings. But a chicom motor, I'd rely more on the FLA motor plate values. Good advice!

 

[sti491]

Thank you everyone. A already have a free 50 amp breaker I think I will use. The instructions are not that clear, just showing where to connect the wires. I am assuming I just hard wire it from the breaker to the compressor.... no need for a switch or plug because I am so close to the breaker box? Agree, or not?

 

[sberry]

Yes, that is fine. 8 cable or 10 in pipe.