New compressor wiring

[02chuck]

Bought a IR 60gal compressor (SS5SL) 5 HP.
Distance to main box is about 5ft.
I used a wire calculator to get a wire size of 8ga. The specs show it uses 21.5amps.
Would the 21.5 amps be start up amps or constant use power? If it constant what would the start amps be?
What size breaker should I get for the power panel?
Thanks

 

[Metal-Marc]

10AWG wire and 30A circuit breaker.

 

[wyliesdiesels]

Bought a IR 60gal compressor (SS5SL) 5 HP.
Distance to main box is about 5ft.
I used a wire calculator to get a wire size of 8ga. The specs show it uses 21.5amps.
Would the 21.5 amps be start up amps or constant use power? If it constant what would the start amps be?
What size breaker should I get for the power panel?
Thanks

what wire size calculator did you use? and what type of wire is the #8?

the 21.5a is the run/FLA current. motors dont list startup current, which is anywhere from 4x-8x the FLA.

To size wire for a motor circuit, you need the FLC current which is found in T430.248. for 5HP thats 28a. you take that figure and multiply by 1.25 which means you need 35a rated wire. so #10 THWN in pipe or #8 NM-b

A 30a breaker may work, or may suffer from nuisance trips

BTW this motor will need to be hardwired unless you use expensive pin and sleeve plugs and outlets.

 

[02chuck]

I just looked up a wire calculator online. Had read somewhere about planning for 50amps so I did my calcs on that.
Planning to put a 60amp cut off box to allow me to shut it off when out of shop.
So would a 40amp breaker be enough or just do a 50amp breaker?
Thanks for response.
Chuck

 

[wyliesdiesels]

I just looked up a wire calculator online. Had read somewhere about planning for 50amps so I did my calcs on that.
Planning to put a 60amp cut off box to allow me to shut it off when out of shop.
So would a 40amp breaker be enough or just do a 50amp breaker?
Thanks for response.
Chuck

but thats not how calcs are done for motor loads...

40a should be fine.

what type of wire are you using?

 

[02chuck]

I was going to get some THHN from HD and enclose it flexible conduit.
C

 

[Norcal]

With THHN, 10 AWG is fine, it's rated for 35A in this application.

 

[mike93lx]

You should be able to get a kit with #10, liquidtite and some fittings all in one bag

 

[wssix99]

The instructions for the compressor will give you the correct answers. There is a good chance the internet will not.

 

[u2slow]

The manual should list recommended wire/circuit sizes. I'd run any 22A nameplated shop compressor on #10... unless its super long run.

 

[Norcal]

The manual should list recommended wire/circuit sizes. I'd run any 22A nameplated shop compressor on #10... unless its super long run.

Except namepate amperes are not OK to size conductors, post #3 explains it and if NM cable is undersized.

 

[u2slow]

@Norcal It is OK to size conductors by your motor nameplate amps. NEC has a special/alternate view on it.

 

[wyliesdiesels]

@Norcal It is OK to size conductors by your motor nameplate amps. NEC has a special/alternate view on it.

no that is incorrect. that may be the case for canada but not in the US

 

[exranger06]

The manual should list recommended wire/circuit sizes. I'd run any 22A nameplated shop compressor on #10... unless its super long run.

I just looked at the manual for my Quincy compressor (60 gallon, 5 HP). It doesn't give any recommendation on wire size or breaker size. It only says:
"The electrical installation of this unit should be performed by a qualified
electrician with knowledge of the National Electrical Code (NEC), OSHA code
and/or any local or state codes having precedence."
"The installation, electric motor, wiring, and all electrical controls must be in
accordance with NFPA 70-1996 National Electric Code, National Electric
Safety Code, state and local codes. Failure to abide by the national, state and
local codes may result in physical harm and/or property damage."
"The customer is to provide disconnect and branch circuit overcurrent protection in accordance with the National Electrical Code and/or any local codes having precedence."

So basically, they just defer to the NEC, and recommend a licensed electrician (who presumably knows what he's doing and knows how to install it following the NEC) wire it up. So the electrician, or whoever is installing the compressor should simply follow the NEC. And the NEC says #10 THHN or #8 NM-b.