will 240 volt a/c unit work without grounding wire?

Status
Not open for further replies.
Re: will 240 volt a/c unit work without grounding wire?

Hello TY (luke warmwater)

No, I am not trying to stir things up. Just here to learn, thought that everyone here wanted to do the same things. Funny things happen when we all share our wealth of information stored upstairs. We all learn together, and become better people because of it.

Take Bob (iwire) for instance. He thought he knew everything, that is till he met up with us home inspectors. (just razzing you back dude!)

If anyone would like to discuss qualifications, I would be happy to do so but before we go there, I must warn you that I have made many veteran electricians very unhappy after I inspected some of their installations. Some things are black and white and others are just black.

Joe Myers
 
Re: will 240 volt a/c unit work without grounding wire?

Originally posted by jmmyers:
Hurk,

Where did you get this information? It was and is my understanding that while it has to be bonded to the metal panels, it can not be used as a grounding conductor.

As far as using the FMC for grounding it is only allowed if the circuit is protected by a 20 amp OCPD or less.
Click to expand...
Thanks again.

Joe Myers
Click to expand...
I think it also has to be the type with the interlocked EGC.

If I am not mistaken, all UL listed FMC is this way, while the stuff that is not listed is not.

I think there is some kind of exception for 6' pieces allowing the use of the FMC without the interlocked EGC.
 
Re: will 240 volt a/c unit work without grounding wire?

Peter,

Could you please verify that information. I am talking about FMC (Greenfield), not AC or MC style cables.

It sounds to me like you are talking more about MC or AC style cable with the bonding strap.

Thanks again.

Joe Myers
 
Re: will 240 volt a/c unit work without grounding wire?

To see it in writing go to 250.118

Roger
 
Re: will 240 volt a/c unit work without grounding wire?

Roger,

Thanks, that is what I was looking for.

Joe Myers
 
Re: will 240 volt a/c unit work without grounding wire?

Now that we have established that FMC can be used as a grounding conductor, lets move on to the situation.

Does anyone forsee a problem with providing two grounding paths for a 240 volt ac unit. Say the green grounding wire and using FMC?

To all those that have been patient, I thank you. It is important to me that I get it right, rather than just get it. I like to make sure I have all the facts straight and I am able to back them up with said facts.

Joe Myers
 
Re: will 240 volt a/c unit work without grounding wire?

Joe, there is nothing wrong with having both the "conduit" and "wire conductor" electrically parallel, and in fact it will effectively provide a reduced resistance which is desirable as far as a fault clearing path.

Roger
 
Re: will 240 volt a/c unit work without grounding wire?

In my opinion, the paralleling of bonding conductors (EGC's) is a good idea. It reduces the fault current on any one path and ensures multiple effective paths if one were to be compromised.
 
Re: will 240 volt a/c unit work without grounding wire?

In the case of the equipment panel (sub panel) would you not want the fault current to flow back to the equipment panel on the neutral bar?

Joe you must be talking about a sub panel. (I hope) Yes if this is a sub panel then the faule current would follow the grounding back to the main service where the grounding conductors and the neutral are bonded together to allow the fault current to return back to it's source (transformer).
Click to expand...
Joe Myers
 
Re: will 240 volt a/c unit work without grounding wire?

Roger,

Would that effectively split the resistence evenly between the two?

Thanks Roger and Bryan for your responses.

Joe Myers
 
Re: will 240 volt a/c unit work without grounding wire?

Joe,

Originally posted by jmmyers:
Roger,

Would that effectively split the resistence evenly between the two?

Thanks Roger and Bryan for your responses.

Joe Myers
Click to expand...
It most likely wouldn't be equal, but this would not be a concern for what would be happening here.

This would simply be "Redundant Bonding"

Roger
 
Re: will 240 volt a/c unit work without grounding wire?

Originally posted by jmmyers:
In the case of the equipment panel (sub panel) would you not want the fault current to flow back to the equipment panel on the neutral bar?
Click to expand...
Now I understand this entire thread.

As far as fault current goes, yes, it would be better to have both the equipment grounding conductors and the grounded conductor to provide paths simultaneously from the subpanel to the service, instead of just the EGC. More paths equals lower resistance equals more chance of tripping the breaker.

Now, having said that, having the grounded conductor in parallel with the equipment grounds anywhere on the load side of the service can cause serious hazards that can kill people and destroy property.

Grounded conductor connected to EGC in a subpanel is not allowed by NEC except in limited circumstances.
 
Re: will 240 volt a/c unit work without grounding wire?

Crossman,

I believe you are on the right track. Although in the case of a 240 volt unit, you only have two hots and one EGC. Does the EGC from the 240 volt unit get attached to the grounding bar or the neutral bar in the equipment panel (sub panel). If you don't know, please just say so. If you do, please back up your statements.

Roger,

A little help please!

Joe Myers
 
Re: will 240 volt a/c unit work without grounding wire?

Joe, Crossman knows the theory and the reasons although he may not have read the first post.

Roger
 
Re: will 240 volt a/c unit work without grounding wire?

By Joe: Does the EGC from the 240 volt unit get attached to the grounding bar or the neutral bar in the equipment panel (sub panel)
Click to expand...
If what your calling a "sub panel" is truly a sub panel there will be a main service disconect that will be else where most likely by where the service enters the building.

With that said, after the first means of disconect for the service it is required to have the grounding conductors kept seperate from the grounded conductor. this keeps unwanted current off all grounding and only the fault current will on this conductor. so there should be only one bond that connects the grounded to the grounding conductor and this should always be at the main service disconect.
So to answer this question: The grounding conductor from the air unit should always be only connected to the grounding bar in this sub panel.

See 250.24(A)(5)
 
Re: will 240 volt a/c unit work without grounding wire?

Roger,

I did not mean to offend, I am certain Hurk is a very smart person. By that statement, like I said eariler, I need the facts to back myself up. No pun intended on anyone, just want the facts and only the facts. :)

Anyway, thanks for all your help, I appreciate everyones replies and have found your posts to be exceptionally informative.

Wayne,

That is what I was looking for, thanks.

So the worst part of this is, really is not bad, it is good. You would have two grounding paths, one with the FMC and one with the green grounding conductor, correct. Even though the breaker that needs to trip is located in the equipment panel (sub panel).

Joe Myers

[ January 25, 2005, 10:21 PM: Message edited by: jmmyers ]
 
Re: will 240 volt a/c unit work without grounding wire?

Originally posted by jmmyers:
Does the EGC from the 240 volt unit get attached to the grounding bar or the neutral bar in the equipment panel (sub panel). If you don't know, please just say so. If you do, please back up your statements.
Click to expand...
Joe, sorry it took me awhile to get back to you.

1) I do know the answer. :)

2) It is not allowed to be connected to the neutral bar.

3) Support for my answer is 2002 or 2005 NEC 250.142(B)

250.24(A)(5) seems to be referring more to bonding the grounded conductor itself instead of using it to bond equipment. 250.142(B) gets directly to the heart of the matter.

[ January 26, 2005, 01:45 PM: Message edited by: crossman ]
 
Status
Not open for further replies.
Top