Feed Through Panels

[bennie]

I got a thorough hammering on the 3 wire feeder issue, so here is another situation I need to resolve.

I installed a 200 amp, main breaker, feed through panel at the service. I feed another panel, at a remote location in the house, from the feed through lugs.

Does the feeder need to be 3 or 4 wire cable?

[ October 10, 2003, 03:47 PM: Message edited by: bennie ]

 

[iwire]

Re: Feed Through Panels

Now that is a great question, I have installed many feed through panels, double and triple tubs, but never have they been service panels, or seperate from each other.

They have always been load side equipment and located side by side.

I will be thinking on that one for a while.

Bob

 

[Ed MacLaren]

Re: Feed Through Panels

Does the feeder need to be 3 or 4 wire cable?

The feeder to the "remote" panel must include an equipment bonding (EGC) conductor, and the grounded (neutral) conductor must be isolated from the enclosure, because it is on the "load side" of the service disconnecting means.

250.142(B) Load-Side Equipment.

Ed

 

[iwire]

Re: Feed Through Panels

I would have to go with Ed on this.

If we used a fused disconnect switch where the service conductors enter the building we would need 4 wires (for single phase) from there to any panel downstream.

I was forgetting the rule talks about the service disconnecting means not a service panel.

 

[ryan_618]

Re: Feed Through Panels

I would have to go with Ed and Bob on this also.

 

[Guest]

Re: Feed Through Panels

What does the manufacturer say about this kind of placement?

 

[roger]

Re: Feed Through Panels

awwt,

What does the manufacturer say about this kind of placement

I would lay money on it that they say to install per the NEC and local codes. :roll:


Roger

 

[jro]

Re: Feed Through Panels

Iwire what are double and triple tubs? Am I correct in thinking these are double and triple mechanical lugs?

 

[iwire]

Re: Feed Through Panels

That would be 2 or 3 - 42 circuit panels fed from one breaker 225 to 400 amp typically to "make" a 84 or 126 circuit panel in separate enclosures.

 

[brian john]

Re: Feed Through Panels

IWIRE:

In highrises (at least in this area) feed throughs are common for riser panels, though they are not service panels.

Good question Bennie. And I agree with the others.

 

[bennie]

Re: Feed Through Panels

I posted this scenario to keep myself from being called an id(ten)t, when I was responding to the 3 wire panels.

Question No.#1.

Now place the second panel directly under the service panel. Use PVC to connect the panels.
Do you still need to install a No.#6 equipment ground conductor from the first panel to the second one?

Question No.#2.

Instead of using the feed through provision, connect the feed to the second panel ahead of the 200 amp main. This would make two service disconnects. Do you still have to connect an equipment ground conductor from the first panel to the second one?.

[ October 10, 2003, 10:12 PM: Message edited by: bennie ]

 

[iwire]

Re: Feed Through Panels

Originally posted by bennie:
Question No.#1.

Now place the second panel directly under the service panel. Use PVC to connect the panels.
Do you still need to install a No.#6 equipment ground conductor from the first panel to the second one?

Yes you would need 4 wires to be NEC compliant

Originally posted by bennie:
Question No.#2.

Instead of using the feed through provision, connect the feed to the second panel ahead of the 200 amp main. This would make two service disconnects. Do you still have to connect an equipment ground conductor from the first panel to the second one?.

No you do not.

But anything down stream from these two service disconnects will need a 4 wire feeder.

 

[bennie]

Re: Feed Through Panels

Then the second panel will have a 2/0 for fault purposes.

The first panel will have a No.#6 for the same purpose.

Is this up?

 

[Ed MacLaren]

Re: Feed Through Panels

Bennie,
Your Question #2 refers to an installation similar to a residential duplex service where there is no main disconnecting means.

The sketch shows how we do a duplex service in my area.
I believe the grounded (neutral) conductor should be kept isolated from equipment enclosures on the load side of the point where the Grounding Electrode Conductor, and Main Bonding Jumper, connect to the grounded (neutral) conductor, wherever that point is.

The following sketch is offered to illustrate basic principles only, and is not intended to represent any actual installation.

Ed

 

[bennie]

Re: Feed Through Panels

Good drawing Ed. There are many apartments, in this area, that have the split buss panels with six mains. Only they are supplied by 3 wire SEC cable.

[ October 10, 2003, 11:41 PM: Message edited by: bennie ]

 

[pierre]

Re: Feed Through Panels

Bennie
I think I can see where you are trying to head with this thread. Your ideas with the grounded conductor being larger and able to conduct fault current even past the first point of disconnect is interesting to me.

Will the grounded conductor carry fault current back to the source (if no EGC were installed), when it is say one or two panels downstream of the service disconnect?

If you were to install it in such a manner (120/240V three wire, two hots and one neutral), would you not be concerned about neutral load current flowing on the metallic paths back towards the source?

Pierre

 

[hurk27]

Re: Feed Through Panels

I was thinking question #2 was like exception 3 in 230.40 where we can run another service from the load side of the meter to feed the garage then the garage panel would be treated like a service with only 3-wire feed.

Bennie: connect the feed to the second panel ahead of the 200 amp main

 

[bennie]

Re: Feed Through Panels

Pierre and Hurk, thanks for your response. I am trying to vindicate myself from the insuations that I am giving out false information.

I am trying to improve my writing skills to be more easily understood when I am making a technical observation. I feel a lot of my procedures are valid.

 

[hurk27]

Re: Feed Through Panels

Bennie years ago I had a (well lets say experience) electrician tell me that there was no reason to separate neutrals and grounds because we didn't need any more wires with stray currents on them. I never really understood him but I think his thinking was of unintentional contact with current carrying conductors but I don't know But with any contact between any grounding fed from one panel with grounding fed from another (3-wire fed) will cause parallel neutral current to form on what ever this grounded metal is and could be a shock hazarded to someone that gets in between it

 

[iwire]

Re: Feed Through Panels

Bennie, I would like you to answer a question.

Why do you not want to use 4 wire feeders for single phase?

I have seen you say it is a waste of our resources.

Well have you been on a construction site lately?

That small amount of material that you consider waste, is I would bet, a fraction of a percent of what leaves the site in a dumpster.

I have seen you say that it provides a smaller wire for fault clearing.

That is true, but in a typical dwelling unit is there any evidence that this smaller conductor can not open the OCPD?

Once we get into jobs with long distances involved there is usually engineering supervision. The engineer should recognize that to clear a fault on a long circuit may take more than NEC minimums.

Basically I am curios why you want to reinvent the wheel?

To any of us that joined this trade in the 1980s like myself seperate grounds and neutrals are the way it is done and to use the neutral as a ground is IMO a step backwards.