# Bare minimum compliant circuit for an ice machine



## Dennis Alwon (May 9, 2009)

I would agree with you based on 240.4 (G)


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## erics37 (May 7, 2009)

Dennis Alwon said:


> I would agree with you based on 240.4 (G)


Thank you, that's what I thought.


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## electricalwiz (Mar 12, 2011)

why would it be #12 and not #10
you are still using a 40 amp breaker though, right?


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## Dennis Alwon (May 9, 2009)

electricalwiz said:


> why would it be #12 and not #10
> you are still using a 40 amp breaker though, right?


 #12 at 75C is rated 25 amps so that takes care of the 23.8 amps minimum circuit ampacity.


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## electricalwiz (Mar 12, 2011)

Dennis Alwon said:


> #12 at 75C is rated 25 amps so that takes care of the 23.8 amps minimum circuit ampacity.


but you are putting it a 40a breaker. I still dont get how you can do that


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## Celtic (Nov 19, 2007)

electricalwiz said:


> but you are putting it a 40a breaker. I still dont get how you can do that


Read it again...



erics37 said:


> Ice-making machine. Nameplate: 208 - 230 VAC single-phase, Max OCPD: 40 amps, minimum circuit ampacity: 23.8 amps.


Its right there on the nameplate :thumbsup:

I know it seems odd, but this is one of the few exceptions in code where OCPD exceeds wire ampacity.
The increase in OCPD is needed for momentary inrush current - not sustained operation.
The decreased wire size is all that is needed for sustained operation.

440.6(A) ...if I recall...


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## electricalwiz (Mar 12, 2011)

Celtic said:


> Read it again...
> 
> 
> 
> ...


I understand that part, but with it drawing 23 amps I thought that was the normal load not start up load


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## Celtic (Nov 19, 2007)

electricalwiz said:


> I understand that part, but with it drawing 23 amps I thought that was the normal load not start up load



It is...what is the ampacity of a #12 THHN at?


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## erics37 (May 7, 2009)

electricalwiz said:


> but you are putting it a 40a breaker. I still dont get how you can do that





electricalwiz said:


> I understand that part, but with it drawing 23 amps I thought that was the normal load not start up load


Small wire on big breakers is typical for motor applications (and similar equipment). Ice machine's biggest load is refrigerant compressor motor.

440.6(A) basically tells you to use the nameplate for all your calcs.

240.4(G) gives you a list of specific applications where you are allowed to break free of typical conductor size/breaker size combinations. Refrigeration equipment is one of the items on that list.


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## electricalwiz (Mar 12, 2011)

erics37 said:


> Small wire on big breakers is typical for motor applications (and similar equipment). Ice machine's biggest load is refrigerant compressor motor.
> 
> 440.6(A) basically tells you to use the nameplate for all your calcs.
> 
> 240.4(G) gives you a list of specific applications where you are allowed to break free of typical conductor size/breaker size combinations. Refrigeration equipment is one of the items on that list.


I get it, had to go look at 310.16
My mind is programmed to #12 is good for 20 amps, #10 for 30 amps. I always knew for motors you could use the nameplate amps as oppposed to the OCPD but without thinking or looking in the code for minimum I would have ran #10
Thanks guys


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## RIVETER (Sep 26, 2009)

erics37 said:


> I'm in an argument with the refrigeration guy and he's being a stubborn jackass, so please vindicate me.
> 
> Ice-making machine. Nameplate: 208 - 230 VAC single-phase, Max OCPD: 40 amps, minimum circuit ampacity: 23.8 amps.
> 
> ...


Why not just install a 30 amp breaker and #10 conductors?


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## Celtic (Nov 19, 2007)

electricalwiz said:


> I get it, had to go look at 310.16
> My mind is programmed to #12 is good for 20 amps, #10 for 30 amps. I always knew for motors you could use the nameplate amps as oppposed to the OCPD but without thinking or looking in the code for minimum I would have ran #10
> Thanks guys



Now that you got...lets mess it up :thumbsup:

I would probably run #10's to the unit....nobody likes to see the lights dim when the compressor kicks in.


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## Celtic (Nov 19, 2007)

RIVETER said:


> Why not just install a 30 amp breaker and #10 conductors?



30A cb would not be sufficient...nameplate calls for a 40....30 will trip.

See my last for #10's


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## erics37 (May 7, 2009)

RIVETER said:


> Why not just install a 30 amp breaker and #10 conductors?


That is what I would prefer to do, HOWEVER:

Two weeks ago they called and said they're putting in a new ice machine and needed a circuit for it. It was going to be a 3 Phase 208 unit requiring a 20 amp circuit or some such. So I went down there, ran a #12 MC cable and a 20 amp breaker and told them to call me when the machine shows up. A week later they called and said the machine is changing into a single phase unit (in fact the one I posted for this thread). They gave me the nameplate info and I knee-jerk reactioned into needing to pull a new MC cable.

Well then I got to thinking about it and decided to look it up in the good book. So I did, and determined that the existing #12 is adequate (barely). So, first off, I'm too busy to pull and make up a wire I already pulled and made up if I don't have to. Second, they've got a compliant install, the machine is only 15 conductor feet away from the panel, so I can't justify the expense of pulling new wire when the current stuff will be safe and perform adequately.

And why would I use a 30 amp breaker if they allow a 40? I don't want to have to go change it out after it keeps tripping at start-up (probably wouldn't but there's always the possibility)


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## Roger123 (Sep 23, 2007)

Celtic said:


> Now that you got...lets mess it up :thumbsup:
> 
> I would probably run #10's to the unit....nobody likes to see the lights dim when the compressor kicks in.


The light dim because #12 has more resistance than #10 which causes more voltage at start up.


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## BBQ (Nov 16, 2010)

Celtic said:


> I would probably run #10's to the unit....nobody likes to see the lights dim when the compressor kicks in.


Actually running 10s to the compressor will cause more dimming of the lights on other circuits than using 12 AWGs for the compressor.


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## Celtic (Nov 19, 2007)

Well how do you like that...


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## Roger123 (Sep 23, 2007)

BBQ said:


> Actually running 10s to the compressor will cause more dimming of the lights on other circuits than using 12 AWGs for the compressor.


E=IR, The only thing changing with the set up of #12 or #10 wire is resistance. The motor will draw the same current at start up with either #10 or #12 wire. So, it would take more voltage at start up with #12 wire.


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## MWayne (Nov 8, 2010)

Is an ice machine considered a continuous load, upping the required ampacity to 29.75?


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## chicken steve (Mar 22, 2011)

Dennis Alwon said:


> #12 at 75C is rated 25 amps so that takes care of the 23.8 amps minimum circuit ampacity.


75C, considering 110.14 (C) (1) (a) (4) ?

~CS~


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## Dennis Alwon (May 9, 2009)

chicken steve said:


> 75C, considering 110.14 (C) (1) (a) (4) ?
> 
> ~CS~


Yep as long as the terminals are rated 75C we can use it. Most terminals and connections are rated 75C. Now 110.14 comes into play when the terminal ratings are not known- we have to assume 60C for under 100 amps but not if it is known.


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## McClary’s Electrical (Feb 21, 2009)

RIVETER said:


> Why not just install a 30 amp breaker and #10 conductors?


Because it's stupid to waste money?


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## Dennis Alwon (May 9, 2009)

MWayne said:


> Is an ice machine considered a continuous load, upping the required ampacity to 29.75?


No, the MCA already includes the 125% - same as on an a/c unit. 

The reason a 40 amp breaker is allowed is because the compressor has overload protection which protects the #12 wire. The breaker is for short circuit or ground fault protection.


Also look at art 440.22. This allows OCPD to be 175% of the branch circuit selection current. 23.8 X 1.75= 41.65 amps so a 40 amp device is compliant.

Of course this is assuming VD is not an issue


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## CADPoint (Jul 5, 2007)

So what was the HVAC's guy POV ? :whistling2:


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## BBQ (Nov 16, 2010)

Roger123 said:


> E=IR, The only thing changing with the set up of #12 or #10 wire is resistance.


It's impedance and also the current drawn by motor inrush will be lower due to the reduced voltage at the windings.




> The motor will draw the same current at start up with either #10 or #12 wire.


Actually during locked rotor and winding up it will draw less current because of reduced voltage. (This assumes it can start with reduced voltage and the wind up time will be extended)



> So, it would take more voltage at start up with #12 wire.


It can't take 'more voltage' the supply is the supply. 




If you run smaller wire to the compressor the impedance in that conductor will lower the current drawn from the supply by the motor causing less voltage drop to other branch circuits.

The smaller conductor works like a reduced voltage starter.


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## erics37 (May 7, 2009)

CADPoint said:


> So what was the HVAC's guy POV ? :whistling2:


He insisted that I needed to have #8 conductors to the machine. At first I told him, "Well not really, but I would have installed #10s if I knew what the machine was going to be." He was being a really stubborn, insistent prick about it. He almost drew me into an argument but after a minute I just took a mental step back and asked myself, "Why am I arguing with this ****** about electrical s**t?" At that point I just walked off and finished hooking up the machine.

Later I overheard him telling the customer (head maintenance guy), "Yeah the electrician thinks the #12 wires will be okay for this 40 amp unit!" And the maintenance guy said, "Yeah? Well I trust him." :thumbup:


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## hardworkingstiff (Jan 22, 2007)

On the subject of what happens with the current with smaller wires.

I've always been instructed that motors tend to use an "x" amount of power. So, if the voltage drops a little, the motor will pull more current in order to compensate for the VD so that it will continue to use "x" amount of power.

Assuming I have a correct understanding, with the smaller wires there will be more resistance which will lower the voltage slightly which will cause the motor to pull more current.

So, using #12 wire will cause the motor load to pull a little more current than it would if #10 wire was used.


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## BBQ (Nov 16, 2010)

hardworkingstiff said:


> On the subject of what happens with the current with smaller wires.
> 
> I've always been instructed that motors tend to use an "x" amount of power. So, if the voltage drops a little, the motor will pull more current in order to compensate for the VD so that it will continue to use "x" amount of power.


That is not as true as often as presented, or at the least it is incomplete. If the mechanical work done by the motor remains constant and the voltage is reduced the current will increase. 

However what we have been talking about is not a situation where the work done by the motor remains constant.

During start up you have a locked rotor condition, which in many cases means the current drawn during locked rotor will be 6 to 8 times the FLA on the motor. If the voltage is reduced at this time the current will drop as well. This is exactly why reduced voltage starters can be used to limit current (and torque). 

http://constructionmanuals.tpub.com/14026/css/14026_251.htm


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## Roger123 (Sep 23, 2007)

I starting to understand this better, thank BBQ


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## BBQ (Nov 16, 2010)

Roger123 said:


> That is what I have read also. So, more current for the motor circuit would equal lights dimming.


Please see post 29 and the link.


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## Roger123 (Sep 23, 2007)

BBQ said:


> Please see post 29 and the link.


I did, just now! Thanks


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## wendon (Sep 27, 2010)

RIVETER said:


> Why not just install a 30 amp breaker and #10 conductors?


That's what I would do. The code is the minimum standard. Most likely, the minimum circuit ampacity takes into account the 1.25 calculation.


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## Celtic (Nov 19, 2007)

erics37 said:


> .... asked myself, "Why am I arguing with this ****** about electrical s**t?" At that point I just ...


... posted it on ET where the argument can run on for days :thumbup:


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## Roger123 (Sep 23, 2007)

Celtic said:


> ... posted it on ET where the argument can run on for days :thumbup:


 How true!!


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## erics37 (May 7, 2009)

Celtic said:


> ... posted it on ET where the argument can run on for days :thumbup:


:laughing: That is entirely true as well.

I'm just glad the HVAC guy wasn't right :blink: Every time I run into that guy on a job he's a **** bag, but first time I dealt with it first-hand.


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## BBQ (Nov 16, 2010)

RIVETER said:


> Why not just install a 30 amp breaker and #10 conductors?





wendon said:


> That's what I would do. The code is the minimum standard. Most likely, the minimum circuit ampacity takes into account the 1.25 calculation.


I would not use a 30 because the manufacturer is telling us they think it needs a 40 amp overcurrent device to handle the start up inrush. 

The motor overload device in the unit also protects the circuit conductors from overload. 

The 40 amp breakers only function is short circuit and ground fault protection.


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## wendon (Sep 27, 2010)

Just because the label allows a maximum overcurrent protection of 40 amps doesn't mean you have to install that size. I've done refrigeration for years and would never install a 40 amp breaker on that size of an ice machine. The RLA of the unit probably would be in the neighborhood of 19 amps. If you use a quality breaker it has a built in allowance for the inrush current. The overload protector will protect the compressor, what will protect the conductors ?


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## Dennis Alwon (May 9, 2009)

wendon said:


> The overload protector will protect the compressor, what will protect the conductors ?


The overload protector will also protect the conductors. If the overload kicks out then the compressor stops. The breaker is for ground fault and short circuit which a 40 will handle just fine.


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## k_buz (Mar 12, 2012)

On the same subject, I understand that #12s are not rated for max 20A in all situations, but lets take an air compressor. Specs say 12A no load, and 23.5A at start up (240V). There is no max fuse size or min circuit ampacity specifically stated. I would see these specs and run #12s on a 25A breaker, but would it be compliant to put these 12s on a 30A breaker?


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## McClary’s Electrical (Feb 21, 2009)

k_buz said:


> On the same subject, I understand that #12s are not rated for max 20A in all situations, but lets take an air compressor. Specs say 12A no load, and 23.5A at start up (240V). There is no max fuse size or min circuit ampacity specifically stated. I would see these specs and run #12s on a 25A breaker, but would it be compliant to put these 12s on a 30A breaker?


Not in that situation.


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## k_buz (Mar 12, 2012)

mcclary's electrical said:


> Not in that situation.


That is what my gut was telling me as well, but could you specifically tell me why not?


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## McClary’s Electrical (Feb 21, 2009)

k_buz said:


> That is what my gut was telling me as well, but could you specifically tell me why not?


A hermatic comressor has internal overload protection, and an air compressor does not.


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## BBQ (Nov 16, 2010)

mcclary's electrical said:


> A hermatic comressor has internal overload protection, and an air compressor does not.


You lost me bud.

I do agree about air compressors not having internal OL protection but they are still required to have OL protection and the same rules apply


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## 10492 (Jan 4, 2010)

I would point out that Eric asked if his installation met the code minumum.

I think most of us would of bid it with a 40A breaker, #8 MC just because we don't do minumum.

Not saying bare minimum is bad or hazardous, FWIW. 

If it meets code, it meets code..


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## micromind (Aug 11, 2007)

It doesn't surprise me that an HVAC guy doesn't understand code requirements for installing HVAC equipment. 

I've had to lead more than a few HVAC guys as well as inspectors through the code for this type of equipment, as well as motors. 

#12s on a 40.....that's nothing; according to the NEC, a 1 HP single phase motor operating on a 120 volt circuit can be fed with #14s and can use a 40 amp breaker. 

A 1-1/2 HP motor on 120 can be fed with #12s and can have a 50 amp breaker. (Yes, they make 50 amp single pole breakers.)

As noted, the motor overload protects the conductors, the breaker provides only short circuit and ground fault protection.


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## BBQ (Nov 16, 2010)

Dnkldorf said:


> I would point out that Eric asked if his installation met the code minumum.
> 
> I think most of us would of bid it with a 40A breaker, #8 MC just because we don't do minumum.


I can't tell you what I would have run, really depends on how far, most likely I would have run 10s on a 40.


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## erics37 (May 7, 2009)

BBQ said:


> I can't tell you what I would have run, really depends on how far, most likely I would have run 10s on a 40.


Machine was about 20 conductor-feet away from the panel. As I mentioned, if I had known the specs on the final machine when I first ran the wire, I would've run #10.

That panel was a real bitch to fish into though, so I'm glad the #12s I ran for the original machine were adequate :laughing: Wasn't looking forward to running new ones.


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## BBQ (Nov 16, 2010)

erics37 said:


> Machine was about 20 conductor-feet away from the panel. As I mentioned, if I had known the specs on the final machine when I first ran the wire, I would've run #10.
> 
> That panel was a real bitch to fish into though, so I'm glad the #12s I ran for the original machine were adequate :laughing: Wasn't looking forward to running new ones.


That short you know the 12s will be fine. 

I had to go to a supermarket on an Island (Nantucket) to wire a refrigerated end cap on an aisle. Our guys had roughed it with 12s and the case was like 22-23 amps. The mechanical contractor had already told the manager we had screwed up. Considering I was alone, the run was long and I did not have 10 MC with me it stayed 12s on a 30. The manger was not impressed, he really felt I was wrong and I expected a complaint call to our office.


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## user4818 (Jan 15, 2009)

BBQ said:


> I had to go to a supermarket on an Island (Nantucket) to wire a refrigerated end cap on an aisle. Our guys had roughed it with 12s and the case was like 22-23 amps. The mechanical contractor had already told the manager we had screwed up. Considering I was alone, the run was long and I did not have 10 MC with me it stayed 12s on a 30. The manger was not impressed, he really felt I was wrong and I expected a complaint call to our office.


Did you kindly explain that #12 is rated for 25 amps?


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## erics37 (May 7, 2009)

BBQ said:


> That short you know the 12s will be fine.
> 
> I had to go to a supermarket on an Island (Nantucket) to wire a refrigerated end cap on an aisle. Our guys had roughed it with 12s and the case was like 22-23 amps. The mechanical contractor had already told the manager we had screwed up. Considering I was alone, the run was long and I did not have 10 MC with me it stayed 12s on a 30. The manger was not impressed, he really felt I was wrong and I expected a complaint call to our office.


There once was an electrician on Nantucket....


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## BBQ (Nov 16, 2010)

erics37 said:


> There once was an electrician on Nantucket....


sad ........ :laughing:


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## erics37 (May 7, 2009)

BBQ said:


> sad ........ :laughing:


I'm taking a break from doing chores, it's the best I could do. I loved the show Wings when i was a kid.


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## hardworkingstiff (Jan 22, 2007)

BBQ said:


> That short you know the 12s will be fine.
> 
> I had to go to a supermarket on an Island (Nantucket) to wire a refrigerated end cap on an aisle. Our guys had roughed it with 12s and the case was like 22-23 amps. The mechanical contractor had already told the manager we had screwed up. Considering I was alone, the run was long and I did not have 10 MC with me it stayed 12s on a 30. The manger was not impressed, he really felt I was wrong and I expected a complaint call to our office.


Just curious, since you didn't mention a name plate max OCP, and the wire is rated for 25-amps and a 25-amp breaker is a standard size, what code section did you use to allow the 30-amp breaker?


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## erics37 (May 7, 2009)

hardworkingstiff said:


> Just curious, since you didn't mention a name plate max OCP, and the wire is rated for 25-amps and a 25-amp breaker is a standard size, what code section did you use to allow the 30-amp breaker?


Article 440 governs installations for refrigeration equipment, which a grocery aisle end cap case would be.

The article gives you specific provisions for how to calculate your circuit and OCPD size if the nameplate is lacking. EDIT: Check 440.22(A). It says 175% of rated load current, which for BBQ's end cap would be 38 or 39 amps or so. Seems a 30 would be a tad on the small side in my opinion.


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## frenchelectrican (Mar 15, 2007)

mcclary's electrical said:


> A hermatic comressor has internal overload protection, and an air compressor does not.


For the Hermatic sealed compressour most case they will useally have interal O/L protection even larger units ( they will useally wired up to the contractor ) 

But for air compressour units if they do NOT have interal o/l's then the game do change on that but if they Do have interal O/L's then you can use the rules as BBQ posted earier in the posting I will done the same thing as well.



BBQ said:


> You lost me bud.
> 
> I do agree about air compressors not having internal OL protection but they are still required to have OL protection and the same rules apply


I agree with that part BBQ but as I mention above the exteral O/L's will use simauir rules ( not the excat the same as art # 440.6 will be posted otherwise I use art # 430 )

Oh yeah for other guys I know BBQ mention sized the conductor to smallest and use the largest OCPD due it will act like autotransfomer to reduce the locked rotor current and some case a hard start kit useally take care of it but if not then will have to upsize the conductor to next size larger but keep the hard start kit on that unit.

Merci,
Marc


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## jp8302 (May 25, 2012)

if a 4o amp overcurrent device is used then #8 is minimum 75' cloumn
#14,12 and 10 are restricted to 15,20 and 30 amp overcurrent devices, higher values in tables are just for calculation purposes. 
#10-30 amps max >or= 23.8 amps 240.4 (b) 30 amp ocpd 
#8 40 amps max, no need to derate either conductor
#10-2 mc minimum or 8-2 mc max


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## BBQ (Nov 16, 2010)

jp8302 said:


> #14,12 and 10 are restricted to 15,20 and 30 amp overcurrent devices,


No they are not restricted to those values for many loads such as motors etc.


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## jp8302 (May 25, 2012)

sorry, your absolutely right; where otherwise permitted such as motor loads #10 could be used as high a 60 something amp circut


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## BBQ (Nov 16, 2010)

jp8302 said:


> sorry,


No problem and welcome to the forum.


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