220/240 wire size and help a dummy

[JCQuick]

what wire gauge should I run for a 220/240 service for my compressor. The person I have directing me says my 12ga is not big enough. The compressor is on a 230v 25amp breaker now and does fine.

Now for the dummy part I've had a had time finding someone to help us finish my electric in my new build so I decided I need to just **** it up and figure it out for myself. Is there an electrical for dummie's book out there or what would one suggest.

 

[davetulk]

good reference chart http://www.cerrowire.com/ampacity-charts 25amp needs 10 gauge wire. 12 gauge max 20 amp.

Dave

 

[JCQuick]

Thank you Dave great help

 

[zmaxmotorsports]

good reference chart http://www.cerrowire.com/ampacity-charts 25amp needs 10 gauge wire. 12 gauge max 20 amp.

Dave

You can use 12g wire on a 25a circuit for ac condensers though.

 

[davetulk]

yeah that funky exception. I assume he was referring to his air compressor

 

[MushCreek]

The breaker that the compressor is on doesn't tell us much. You need to read the plate on the motor so you can tell what the actual load is. It might run fine on a 20A breaker- or not.

 

[CNGsaves]

The breaker that the compressor is on doesn't tell us much. You need to read the plate on the motor so you can tell what the actual load is. It might run fine on a 20A breaker- or not.

^ ^ ^ Not necessarily.

What GJ Sparky's have taught us over and over is . .
. . .
. . . . . . HP on compressor motor plate is what determines wire size & breaker.

OP . . . . post up PIC of motor plate and GJ Sparky's will tell you details.

 

[JCQuick]

^ ^ ^ Not necessarily.

What GJ Sparky's have taught us over and over is . .
. . .
. . . . . . HP on compressor motor plate is what determines wire size & breaker.

OP . . . . post up PIC of motor plate and GJ Sparky's will tell you details.

Will do when I get home tonight

 

[Falcon67]

I'm running 10 to the lift mostly because that's what the manual says is required - 30A circuit. Motor is only 3HP, rated 14A - but bigger wire won't hurt anything. Post the motor plate and you'll get a good recommendation, but usually 10 is good for 3~5HP compressor motors. My 3.2 runs on 12 Gage without issues.

 

[davetulk]

If the unit only requires 20amp that is fine...but code mandates if he is using a 25amp breaker must be 10 gauge. He can swap out the breaker to a 20amp and be within code if the compressor only requires a 20amp circuit.

For wire gauge you have to go by the protection device not the service device. Wire gauge can be bigger than protection device...but not the other way around as wire can fail before protection device causing a fire hazard. As it sits right now 12 gauge wire on a 25amp circuit breaker is not within code.

 

[theoldwizard1]

Home Depot, Lowes and probably Menards have have DIY home electric books.

Distance from the breaker to the outlet also plays into wire size. GENERAL "rule of thumb"

15A - 14 gauge
20A - 12 gauge
30A - 10 gauge

"Romex" (a brand name for 2 or 3 insulated wire plus a bar ground inside of a outer insulation) is what is used to wire most house/garage circuits. There is wire for interior use (trade name NM-B) and exterior (including buried) use (trade name UF-B). For a rookie DIYer, this will likely be all you will ever use.

Individual insulated wire (trade name THHN/THWN) must be run in a conduit.

There are many other types of wire for specific purposes. Not something most rookie DIYers would take on.

 

[alfredeneuman]

good reference chart http://www.cerrowire.com/ampacity-charts 25amp needs 10 gauge wire. 12 gauge max 20 amp.

Dave

That chart is for general wiring for lighting and such.
Motors, AC equipment and welders are not subject to the GENERAL "rule of thumb"

 

[toyotadriver]

I would run 10ga and put it on a 30 amp breaker. Did that in my shop and it's fine.

You might consider running heavier ga wire if you think you might upgrade the compressor eventually.

 

[wyliesdiesels]

^ ^ ^ Not necessarily.

What GJ Sparky's have taught us over and over is . .
. . .
. . . . . . HP on compressor motor plate is what determines wire size & breaker.

OP . . . . post up PIC of motor plate and GJ Sparky's will tell you details.

This shouldve been the first response not the 6th with an additional 6 comments after it without the OP giving the necessary info.

For motor circuits u start off with the HP rating then go from there.

 

[alfredeneuman]

For those that don't have access to a Code book (or don't know where to look) there are online calculators for motors that will do the computations for you.

Look for "2014 nema motor data calculator"

 

[JCQuick]

I'm here folks thanks for all the reply's. main reason I'm asking for help is my electrician's baled on me forcing me to get someone that says he knows so I'm the QC on this

Anyway as promised motor plate pic

 

[wyliesdiesels]

Its SPL HP. Lovely :

FLA is 21a so its prob close to 5HP.

U need #8 NM-b or #10 THN in pipe.

If panel is not within site and farther than 50' away then u will need a disconnect as well.

Does this have a starter or integral overload on the motor(red button on end)?

 

[JCQuick]

Its SPL HP. Lovely :rollseyes:

FLA is 21a so its prob close to 5HP.

U need #8 NM-b or #10 THN in pipe.

If panel is not within site and farther than 50' away then u will need a disconnect as well.

Does this have a starter or integral overload on the motor(red button on end)?

its rated at 5hp With the up and over and down to where it will be located will maybe use 40ft of wire. But I do want to put a switch in the shop within inch's of the main panel to control the compressor

 

[wyliesdiesels]

its rated at 5hp With the up and over and down to where it will be located will maybe use 40ft of wire. But I do want to put a switch in the shop within inch's of the main panel to control the compressor

Not according to the motor plate which says its special

But regardless, the wire sizes i posted are whats needed for 5HP

If u want a switch u will need a starter. Does the pressure switch not have off/auto lever?

 

[sberry]

If its not listed by hp I wouldn't lose sleep with a 10 cable and a 30 on it but skip the switch next to the panel. There is absolutely no reason to add extra equipment not needed here especially to a simple motor circuit. The best "safety" for these is a ball valve on the tank, shut it off.

 

[JCQuick]

Not according to the motor plate which says its special

But regardless, the wire sizes i posted are whats needed for 5HP

If u want a switch u will need a starter. Does the pressure switch not have off/auto lever?

OK. yes there is a starter and a on/off switch on the pressure switch. but I'm installing the compressor outside behind the shop. I don't want to have to walk out back to turn it on and off

 

[wyliesdiesels]

OK. yes there is a starter and a on/off switch on the pressure switch. but I'm installing the compressor outside behind the shop. I don't want to have to walk out back to turn it on and off

Ok well u will need a disconnect at the compressor then.

U can use a light switch wired in series with one side of the contactor coil to turn it on and off. Just make sure to turn it off when its not running.

Also, as sberry mentioned, i would put a valve inline where the air line comes into the shop. Maybe even put the switch next to it.

 

[JCQuick]

If its not listed by hp I wouldn't lose sleep with a 10 cable and a 30 on it but skip the switch next to the panel. There is absolutely no reason to add extra equipment not needed here especially to a simple motor circuit. The best "safety" for these is a ball valve on the tank, shut it off.

I think a simple cut off would be fine better than using the breaker. remembering to walk out back to turn the compressor off and on is not an option its in my attached 3 car now and I hear it when it comes on at 3 am because we didn't walk over and turn it off

I did get a good idea from this so far I may relocate my plan for cut off switch and airline to shop location. thank you

 

[sberry]

An off/on may be different than a service disconnect. You need a motor rated switch. In theory if it doesn't leak it doesn't run.
We had a motor problem on one a while back, shut the service valve off, had it down a week, fixed the motor, turned the breaker back on, Only time its ever turned off is power outage.

 

[Norcal]

An off/on may be different than a service disconnect. You need a motor rated switch. In theory if it doesn't leak it doesn't run.
We had a motor problem on one a while back, shut the service valve off, had it down a week, fixed the motor, turned the breaker back on, Only time its ever turned off is power outage.

A "service disconnect" disconnects the service entrance conductors, HVAC service "techs" seem to persist in using the service disconnect labels supplied w/ safety switches when they should be discarded.

 

[wyliesdiesels]

An off/on may be different than a service disconnect. You need a motor rated switch. In theory if it doesn't leak it doesn't run.
We had a motor problem on one a while back, shut the service valve off, had it down a week, fixed the motor, turned the breaker back on, Only time its ever turned off is power outage.

U only need a motor rated switch IF its switching the motor load.

The OPs compressor has a starter so all he needs is a light switch wired inline with the contactor coil.

 

[JCQuick]

So a service disconnect would be the best way to go?

 

[wyliesdiesels]

So a service disconnect would be the best way to go?

Its not called a SERVICE disconnect as Norcal explained above

Just a disconnect.

But it needs to be near the compressor.

If u want a seperate shut off switch inaide then u can use the light switch method i suggested above.

 

[theoldwizard1]

Just a disconnect.

But it needs to be near the compressor.

At least in commercial applications the disconnect must be able to be "locked" in the OFF position by the person servicing the appliance.

 

[sberry]

A "service disconnect" disconnects the service entrance conductors, HVAC service "techs" seem to persist in using the service disconnect labels supplied w/ safety switches when they should be discarded.

I am agreeing with you, I realize this, its the point I was making with OP, a remote is not a service disc.