# neutral for AHU?



## truelight (Mar 17, 2010)

Do 3 ph AHUs or 1 ph 208V Furnace Units ever get a neutral? Or is that a typo on my prints?


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## raider1 (Jan 22, 2007)

There may be some units that require a neutral. They may be tapping off the feed to supply control voltage or maybe a light or other 120 volt loads.

Ask the electrical design professional who drew the prints for clarification.

Chris


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## Selectric (Aug 18, 2009)

Or ask for the approved submittals on the AHU.:thumbsup:


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## HARRY304E (Sep 15, 2010)

truelight said:


> Do 3 ph AHUs or 1 ph 208V Furnace Units ever get a neutral? Or is that a typo on my prints?


Yes they do.....do you have a cut sheet for the units..


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## truelight (Mar 17, 2010)

Right now all i have is the unit schedule in the plans and i cant see any info that makes that clear. I just saw the lines on the circuit symbol and it was 3 lines and a ground for the 208 1 ph fu and 4 lines and a ground for the 3ph AHU


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## HARRY304E (Sep 15, 2010)

truelight said:


> Right now all i have is the unit schedule in the plans and i cant see any info that makes that clear. I just saw the lines on the circuit symbol and it was 3 lines and a ground for the 208 1 ph fu and 4 lines and a ground for the 3ph AHU


I would follow the prints,, but you should be able to contact the enginer that drew the prints ..


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## Dennis Alwon (May 9, 2009)

I did a single phase unit about 25 years ago-- I think it was an Amana unit that req. a neutral. I have not seen one since then-- it would not surprise me that there are some.

A word of caution-- I believe that the neutral should be no smaller then the eqc. Some will argue this and we have had some long thread on it but I would cover my butt on it.


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## raider1 (Jan 22, 2007)

Dennis Alwon said:


> A word of caution-- I believe that the neutral should be no smaller then the eqc. Some will argue this and we have had some long thread on it but I would cover my butt on it.


Correct, if the neutral is smaller than the required EGC then during a phase to neutral fault the neutral conductor may not be adaquate to carry the fault current to trip the overcurrent protective device.

Chris


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## running dummy (Mar 19, 2009)

I remember I was on a big job and when we pulled the fire pump controller feed they spec'd a neutral... There wasn't even a lug to land it on in the controller when I trimmed it out :lol:


But we pulled it anyway and I taped it off and put it out of the way in the controller anyway...


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## sokoservices (Feb 23, 2010)

According to the NEC all disconnects require you to pull a neutral to them.... THere for there should be a disconnect at the AHU and it should have a neutral in it, weather its used or not.


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## MDShunk (Jan 7, 2007)

truelight said:


> Do 3 ph AHUs or 1 ph 208V Furnace Units ever get a neutral? Or is that a typo on my prints?


Sometimes. Especially if they have a receptacle in them and they're not using a 208x120 control transformer.


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## raider1 (Jan 22, 2007)

sokoservices said:


> According to the NEC all disconnects require you to pull a neutral to them.... THere for there should be a disconnect at the AHU and it should have a neutral in it, weather its used or not.


Please enlighten me on where in the NEC a neutral is required at ALL disconnects, as I can't seem to find that requirement.

Chris


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## Dennis Alwon (May 9, 2009)

raider1 said:


> Please enlighten me on where in the NEC a neutral is required at ALL disconnects, as I can't seem to find that requirement.
> 
> Chris


You are so tactful ? :thumbup:


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## raider1 (Jan 22, 2007)

Dennis Alwon said:


> You are so tactful ? :thumbup:


Thanks, I was feeling quite chipper this morning when I posted that.:laughing: :thumbsup:

Chris


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## sokoservices (Feb 23, 2010)

Gents,
Ill find it later. It might be a local code.. but Ill find it. I though it was in the wiring methods section or the services section.


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## raider1 (Jan 22, 2007)

sokoservices said:


> Gents,
> Ill find it later. It might be a local code.. but Ill find it. I though it was in the wiring methods section or the services section.


I'll be waiting with bated breath (Or is that bad breath???). :laughing::thumbup:

Chris


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## sokoservices (Feb 23, 2010)

raider1 said:


> I'll be waiting with bated breath (Or is that bad breath???). :laughing::thumbup:
> 
> Chris


Smart a$$


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## raider1 (Jan 22, 2007)

sokoservices said:


> Smart a$$


I know, I am just messing with you, it is all in good fun.:thumbup:

My point is that barring any local amendment, there is not an NEC requirement that all disconnects must have a neutral ran to them.:thumbsup:

Chris


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## Rockyd (Apr 22, 2007)

I see Chris has had his usual vitamins for the day - two code sections and one clause...:thumbup::laughing:...

He's a pretty sharp inspector too. Somehow, if it's not NEC don't t think your going to get one by him:jester:


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## Dennis Alwon (May 9, 2009)

Soko the 2011 nec requires a neutral to be pulled into switches that control lights-- art 404.2(C)-- with a few exceptions. Is this what you are thinking???


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## Rockyd (Apr 22, 2007)

I'm thinking he has his wires crossed. The articles I believe he needs to look at is 250.24(C). That should quantify the problem....:whistling2:


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## sokoservices (Feb 23, 2010)

Rockyd said:


> I'm thinking he has his wires crossed. The articles I believe he needs to look at is 250.24(C). That should quantify the problem....:whistling2:


 
This is the one.... Doesnt this mean you have to have the Neutral to the Disconnect even if your not using it????? Thats how i read it. It was also a question on the Masters Exam here in virginia.... Its also high lighted as a test question answser according to Mike Holt.......

HELP me if i miss read this.....


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## Smoke (Feb 25, 2011)

truelight said:


> Do 3 ph AHUs or 1 ph 208V Furnace Units ever get a neutral? Or is that a typo on my prints?


frequently, engineers are morons (problem is you can get a degree without field experience, this will plague our trade till the end of time). there are occasions when you have to pull neutrals but mostly you do not. there is frequently control transformers to handle this issue.


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## raider1 (Jan 22, 2007)

sokoservices said:


> This is the one.... Doesnt this mean you have to have the Neutral to the Disconnect even if your not using it????? Thats how i read it. It was also a question on the Masters Exam here in virginia.... Its also high lighted as a test question answser according to Mike Holt.......
> 
> HELP me if i miss read this.....


That section is titled *Grounded conductor brought to service equipment.* There fore it only applies to service equipment and not to general disconnects.

Chris


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## Smoke (Feb 25, 2011)

HARRY304E said:


> I would follow the prints,, but you should be able to contact the enginer that drew the prints ..


lmao!! if you find an engineer who can draw prints right let me know, ive never seen it.
apparently no one taught them you cant put a round peg in a square hole lol


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## sokoservices (Feb 23, 2010)

raider1 said:


> That section is titled *Grounded conductor brought to service equipment.* There fore it only applies to service equipment and not to general disconnects.
> 
> Chris


 
Not always true. I had plans fail becasue the neutral was not shown and they said it was a non fused SERVICE DISCONNECT.. There for it was required to have a neutral even though its not used. You attach it at the panel and wire nut it off at the disconnect.


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## raider1 (Jan 22, 2007)

sokoservices said:


> Not always true. I had plans fail becasue the neutral was not shown and they said it was a non fused SERVICE DISCONNECT.. There for it was required to have a neutral even though its not used. You attach it at the panel and wire nut it off at the disconnect.


Then whoever failed the plans does not know the definition of *Service equipment*. Service equipment is a defined term in Article 100.



> *Service Equipment*. The necessary equipment, usually consisting of a circuit breaker(s) or switch(es) and fuse(s) and their accessories, connected to the load end of service conductors to a building or other structure, or an otherwise designated area, and intended to constitute the main control and cutoff of the supply.


Note that the definition states that the service equipment is connected to the load end of service conductors. Therefore using this definition a standard disconnect for a motor or other piece of equipment would not be service equipment.

Chris


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## racerjim0 (Aug 10, 2008)

truelight said:


> Right now all i have is the unit schedule in the plans and i cant see any info that makes that clear. I just saw the lines on the circuit symbol and it was 3 lines and a ground for the 208 1 ph fu and 4 lines and a ground for the 3ph AHU


If your just bidding the job, bid it with a neutral. If you get/have the job confirm what is actually getting installed with the HVAC guy before you install anything. It may save you a few bucks and a few headaches especially if someone allows an alternate valued engineered unit.


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