# compressor



## Black Dog (Oct 16, 2011)

karl_r said:


> I'm about to install a new compressor and just discovered that the cable between pressure switch and motor is 14AWG while motor is rated at 17.5FLA.
> One doesn't need to be a scientist to realize that the cable is not right but now I wonder what should I do. I still have warranty but it's going to be a pain to have it fixed. This is a brand new compressor made in USA.
> 
> 
> ...


Hook it up and amp that wire I'll bet it is caring that much current.


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## hardworkingstiff (Jan 22, 2007)

When it comes to motors, isn't 14 good for 20 amps?

Is this factory wiring or contractor wiring?


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## Sdavey1 (Oct 29, 2011)

With the lower supply voltage the current draw will increase. the motor will last for a while but eventually the windings will breakdown and fail. If he wants it done though and its his money, I say drive on and hook it up and watch and learn when it starts to breakdown.


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## JRaef (Mar 23, 2009)

hardworkingstiff said:


> When it comes to motors, isn't 14 good for 20 amps?
> 
> *Is this factory wiring or contractor wiring?*


That's the salient point. WE can't use 14ga for that if wired in the FIELD, The NEC says FLA x 1.25, so that puts us at almost 22A. Then the wire is sized based on the charts (310-16) and type of wire, but never more than the 75C column, so never MORE than 20A. 

However that doesn't mean the *factory *can't. They can use higher temperature wire etc., as long as the entire ASSEMBLY has been submitted and listed by UL or some other NRTL, and those wires are counted as part of the ASSEMBLY and never leave the designed raceway as submitted. That sort of thing happens a lot. In that case, 14ga THHN or SIS at 90C is rated for 25A, good to go!

But if the compressor DEALER added the pressure switch for you or some other contractor did it in the field, something like that, then it's not going to fly.


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## Rollie73 (Sep 19, 2010)

As per table 45 in the CEC....the motor current will increase by 10% for a 230 volt motor run on 208.

The motor is a 3hp and is rated at 17 amps which will increase to 18.7 amps when used at 208.

As for that #14 carrying 18.7 amps, I wouldn't even think twice about it. The compressor is factory built and probably UL listed the way it is. Just run it.


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## karl_r (Nov 5, 2012)

Rollie73 said:


> As per table 45 in the CEC....the motor current will increase by 10% for a 230 volt motor run on 208.
> 
> The motor is a 3hp and is rated at 17 amps which will increase to 18.7 amps when used at 208.
> 
> As for that #14 carrying 18.7 amps, I wouldn't even think twice about it. The compressor is factory built and probably UL listed the way it is. Just run it.


is it legal to run at 208 if the plate says 240V only?


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## Rollie73 (Sep 19, 2010)

I can't think of anything in the code book the specifically forbids it to be done.
We both know that it would be extremely rare that you would find a supply voltage of exactly 240 volts and that remained steadily at 240 volts. 

I think its fine to do so.


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## JRaef (Mar 23, 2009)

karl_r said:


> is it legal to run at 208 if the plate says 240V only?


Most motors 10HP and under are designed as 220V +15%, -10%, then labeled as "208-230V". They do that because 220-10% = 198V, which is OK for utility required specs of +-5% of nominal, so 208-5% is 198 as well. Then the other end is fine too because 220 +15% = 253V, and the utility would be 240 +5% so 252V.


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## hardworkingstiff (Jan 22, 2007)

karl_r said:


> is it legal to run at 208 if the plate says 240V only?


Not where I live. If the motor says 240V instead of 208-230 (or 240) then the local AHJ will turn it down if you wire it to 208.


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## sparky278 (Apr 8, 2015)

karl_r said:


> I'm about to install a new compressor and just discovered that the cable between pressure switch and motor is 14AWG while motor is rated at 17.5FLA.
> One doesn't need to be a scientist to realize that the cable is not right but now I wonder what should I do. I still have warranty but it's going to be a pain to have it fixed. This is a brand new compressor made in USA.
> 
> 
> ...


 
sometimes these motor will have a very small note on the bottom of the name plate stating it will run on 208. also look at the SF rating if it is rated 1.15 the insulation temperature and winding is good for 208. as for the wire factory installed let r eat......


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## karl_r (Nov 5, 2012)

sparky278 said:


> sometimes these motor will have a very small note on the bottom of the name plate stating it will run on 208. also look at the SF rating if it is rated 1.15 the insulation temperature and winding is good for 208. as for the wire factory installed let r eat......


there is nothing about 208V but I checked with local inspector and he said he's fine because there is no regulation about that. I guess I'll just go ahead and do it, but I don't think it's gonna last for a long time


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## ampman (Apr 2, 2009)

Could the wire be from the PS to a starter?


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