Air compressor plug....

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Jamesco said:
Look at 240.4 (D) (7)
#10 ampacity 30 amps.

Also look at 240.4 (G) & Table 240.4 (G) for overload protection.
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Jamesco said:
Look at 240.4 (D) (7)
#10 ampacity 30 amps.

Also look at 240.4 (G) & Table 240.4 (G) for overload protection.
Click to expand...

Okay thank you for the insight! I thought motors breakers we able to be upsized for some reason... is that only once conductors are sized over #10? I have always applied 240.4 (d) 7!in residential setting.... I just thought motors were different... for some reason yesterday I was getting confused with 445.13 for generators and motor nameplates and I was wrong on that too. Conductors from gen set terminals to first distribution device are 1.15... thanks for the help! looks like I’ll be running pipe and finding a helper to pull some wires!
 
Jamesco said:
No, not on a 50 amp breaker.


Well actually for figuring the branch circuit wire size you do not use the motor nameplate amps. You have to use the HP rating as found in Table 430.248. The nameplate on the motor says 5hp at 230V.
Using Table 430.248 says 5hp at 230V use 28 amps. 28 X 1.25% = 35 amps. #8cu wire.
Size of breaker at the panel, use a 40 or 50 amp breaker. Use the Leviton 6-50R receptacle. Pretty much what the electrician before you did.
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Not questioning you on 240.4 (d) 7, but why does the square do slip stick give me a 60a fal22060 on #10 wire? Are they utilizing 430.52? So after #10 conductor size 240.4 d 7 doesn’t apply? I Just noticed that the slip stick is from 2008 and is probably somewhat out of date...
 
ctaylo360860 said:
Not questioning you on 240.4 (d) 7, but why does the square do slip stick give me a 60a fal22060 on #10 wire? Are they utilizing 430.52? So after #10 conductor size 240.4 d 7 doesn’t apply? I Just noticed that the slip stick is from 2008 and is probably somewhat out of date...
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28A * 1.25 = 35A: #10Awg @75C has an ampacity of 35A.

28A * 2.50 = 70A: The circuit breaker could be as large as 70A.
 
david luchini said:
28A * 1.25 = 35A: #10Awg @75C has an ampacity of 35A.

28A * 2.50 = 70A: The circuit breaker could be as large as 70A.
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See that’s what I came up with as well... and thought I’d be okay....! jamesco pointed out 240.4 d(7)
david luchini said:
28A * 1.25 = 35A: #10Awg @75C has an ampacity of 35A.

28A * 2.50 = 70A: The circuit breaker could be as large as 70A.
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that’s what I also came up with.... and using exception 2 if the breaker isn’t sufficient for starting current I can use exception (c) and actually go up to 300%.... does it mater if it’s not a fal22060 and it’s just a 2 pole miniature square d qo breaker ?
 
ctaylo360860 said:
Not questioning you on 240.4 (d) 7, but why does the square do slip stick give me a 60a fal22060 on #10 wire? Are they utilizing 430.52? So after #10 conductor size 240.4 d 7 doesn’t apply? I Just noticed that the slip stick is from 2008 and is probably somewhat out of date...
Click to expand...

Because of the 6-50R receptacle installed on the #10 branch circuit wiring that's connected to a 60 amp breaker. It's not idiot proof. What if? What happens when you leave the job and never look back? Get rid of the 50 amp receptacle then ask me your question again.

Unplug the air compressor from the 50 amp receptacle. Move the compressor to another area or room. Does your installation still meet code?
 
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ctaylo360860 said:
See that’s what I came up with as well... and thought I’d be okay....! jamesco pointed out 240.4 d(7)

that’s what I also came up with.... and using exception 2 if the breaker isn’t sufficient for starting current I can use exception (c) and actually go up to 300%.... does it mater if it’s not a fal22060 and it’s just a 2 pole miniature square d qo breaker ?
Click to expand...

240.4(D)(7) doesn't apply.

The circuit breaker doesn't have to specifically be an FAL type.
 
Jamesco said:
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Because of the 6-50R receptacle installed on the #10 branch circuit wiring that's connected to a 60 amp breaker. It's not idiot proof. What if? What happens when you leave the job and never look back? Get rid of the 50 amp receptacle then ask me your question again.
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Maybe I replied to the wrong person, but after I found out that the plugs are only rated for. 3 hp motor I decided I was going to set a disconnect instead... see that’s why I originally thought it made more sense to install the #10 conductors on 30amp receptacle fused on a 50amp breaker, because later I didn’t want someone to plug in an 50a device that would pull more than the conductors are rated for. So basicslly if I was using a receptacle and plug 240.4 d7 allies and I’m only good for 30amps on #10, but because I’m setting a disconnect with adequate voltage, amperage, and hp rating I can get away with using the exceptions in 430.52, if I needed.... sorry for the mix up
 
Jamesco said:
Because of the 6-50R receptacle installed on the #10 branch circuit wiring that's connected to a 60 amp breaker. It's not idiot proof. What if? What happens when you leave the job and never look back? Get rid of the 50 amp receptacle then ask me your question again.

Unplug the air compressor from the 50 amp receptacle. Move the compressor to another area or room. Does your installation still meet code?
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I completely Agree with you that’s why I thought i thought it made sense of to initially install the 30a receptacle instead of a 50amp. I agree most likely the air compressor will move and they will try and plug something with a 50 amp end into the receptacle and the #10 conductors are not sized for a load over 35 amps.... basically if the receptacle and plug were 5hp rated then I could use this as a type of disconnect snd I see why in a plug receptacle situation why a 50amp receptacle should be fed with #8 and put on a 50amp breaker... now if you were t use a non fused disconnect I should be able to get away with #10’s and a max 70 amp breaker. Not saying that this is what I will do? But if this were a code related question on a test and they eanted to know the minimum size conductor or maximum size breaker 430.52 exception no 2 (c) allows the upsizing for starting current....
 
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ActionDave said:
Yes you are but that doesn't change the fact that you could go up to 70.
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Yes up to 250%. 28A X 250% = 70 amp. That's code.

What bothers me you could have a 5hp motor with a nameplate FLA of 28 amps that is feed from #10 wire. Doesn't leave much room for changing connected shaft loads or VD on the branch circuit.

Code or not I wouldn't use #10 to feed a 5hp 230V single phase motor. Has nothing to do with the sizing of the OCPD.

Jim
 
This is a perfect example of OEM motor screwing things up.

I don't understand how motor MFGs get away with this.

I was on a job to replace 2 existing cooling towers with 2 new ones (exact replacement old ones froze up) The old towers had 20 hp motors wired out of a switchboard with a starter and an instantanoius trip breaker and the motor name plate was about 30 amps at 480/3/60

The new towers showed up and the motor nameplate said 20 hp alright but the nameplate amps was 45. This wasn't going to work and would cost a fortune to rewire.

They were Marathon motors. I called Marathon and they told me " we do this all the time OEM motors we can put anything on the name plate we want" Turns out they were 30 hp motors rebaged as 20s and shipped out marked 20 hp and 45 amps.

The HVAC contractor bitched and they eventually shipped two new motors and a factory guy to install them. I have run into this before usually on HVAC equipment with OEM motors where the name plate amps is way way off the code amps

How do they get away with this??
 
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