Additional Panel

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Re: Additional Panel

Originally posted by highkvoltage:
Your conductors would have to rated for 125%. To feed a 100 amp subpanel and for you to have the ability to have 100 amps at the subpanel your branch circuit would have to be #1 THHN (Table 310.16).
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Highkvoltage, you do not have to feed a 100 amp panel with 1 AWG to use it at 100 amps, 3 AWG is fine.

Most 100 amp panels are only rated 100 amps non-continuous and for that 3 AWG is correct.
 
Re: Additional Panel

Originally posted by bennie:
Bob: I am sorry this subject upsets you.
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Going against the establishment does not upset me, and I am happy to learn other things about my trade. :)

What upsets me is when you make misleading statements about the requirements we must install electric equipment under. :(

Originally posted by bennie:
There is other subjects a mouse click away.
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I am not going anywhere, :D

[ March 03, 2004, 07:13 PM: Message edited by: iwire ]
 
Re: Additional Panel

I didn't say you couldn't feed a 100 amp panel with a 100 CB. I am stating you have to size your branch circuit for continuous load i.e. 125%. At least that is what they enforce here and I feel they are correct. If we use #3 we would only be allowed to fuse it at 80 amps at the main panel.
 
Re: Additional Panel

High

A 100 amp breaker, 100 amp panel and 3 awg are correct for 100 amp loads up to 3 hrs long.

If they are making you use 1 AWG for this they are wrong.
 
Re: Additional Panel

Highkvoltage, please quote a code article if you feel they are correct.

Roger
 
Re: Additional Panel

Highkvoltage, I don't see any thing in that 250.122 table that says anything about THHN being used, why are you saying to use THHN wire ????

John

[ March 03, 2004, 07:32 PM: Message edited by: drg ]
 
Re: Additional Panel

iwire. For the feeder size I believe the AHJ uses 215.2(A)(1). I am not saying I totally agree with them but I have to live with guys and believe me there are days. I never stated that using 3 wires instead of 4 was a NEC violation. I stated that they would not pass it here and I used good basic wiring methods in my explanation. Hey if someone wants to run one wire to a panel good luck.

For sake of arguement. Six panels on a wall are all service panels (service disconnects)? As long as they were feeding six stores or six apartments and each had a main CB. If they were for one location (one store or any business) you would have a problem. One would have be the main service disconnect large enough to feed it load plus the other five load centers/panels.

More than six then it doesn't matter you have to have a main service disconnect no matter what. 230.71

Not upset just felt misunderstood. Have a nice day. :)
 
Re: Additional Panel

drg. Use what ever wire you would like to choose from the 90 deg C. Since THHN is most common I used that based on cost and common sense.
 
Re: Additional Panel

Hi Bennie,

Pierre: I fail to see a fire danger or a shock hazard with 3 wires to a panel. Two active line conductors, one equipment ground conductor from the service neutral bus. This is the same as using the neutral to ground the panel.
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Well, no. At the second panel you stated that there are no 120V loads. All loads are line to line. The third conductor which is grounded at the sevice panel is meerly and extention of that potential. This does not constitute "neutral grounding" because there is no "neutral" current at the second panel.
 
Re: Additional Panel

All metal is connected to the main neutral bus. Therefore the neutral is used for grounding all metal.
 
Re: Additional Panel

bennie. Granted the grounded conductor and the equipment grounding conductor are bonded at the service disconnect but that is as far as it goes. The only conductor used for grounding anything in the electrical system in the equipment grounding conductor and to think otherwise is very wrong. The NEC clearly states that in Article 250. To use the grounded conductor for a equipment ground is very unsafe. I have enjoy this discussion very much. Thank you all.
 
Re: Additional Panel

Iwire : Imo I agree with the inspector. Wanting the 100 amp panel fed with #1 awg wire only if the termination point is rated for 60 degree c

I base my option on sec 408.13

Phil c
 
Re: Additional Panel

Phil, it is highly unlikely you will find a 100 amp panel with 60 C rated terminals.

215.2(A)(1) tells us feeder must be sized at 125% of the continuous load.

The non-continuous load on a 3 AWG THWN, 100 amp OCPDs and panels can be 100 amps.

You can not load a typical 100 amp panel to 100 amps continuous, it would have to be specifically rated for 100% loading.

The only time you would be required to use 1 AWG to feed a 100 amp panel is

1)Where the assembly, including the overcurrent devices protecting the feeder(s), is listed for operation at 100 percent of its rating,

And

2)The continuous load is above approx. 90 amps.

I have never seen both those conditions.

What I see is when the continuous load is above 80 amps you use a larger than 100 amp panel and feeder.
 
Re: Additional Panel

"All metal is connected to the main neutral bus, therefore the neutral is used to ground all metal."

At the first point of disconnect, in premise wiring (generally the type of work all inside wiremen do), we have single point grounding. The grounded conductor (neutral), the equipment grounding conductor, the main bonding jumper and the grounding electrode conductor are all bonded (connected) together.

The 'grounding' is enabled by the grounding electrode, to ground the system.

I will admit (THIS IS STRICTLY MY OPINION!!!) that we should not have to ground at the first disconnect, as the grounding has already occurred at the utility transformer. The utility should be bringing 4 conductors to a single phase service, and 5 conductors to a 3 phase service. Years ago they somehow convinced everyone that the way we install now is how it should be performed. It saves the utility company lots of $$$$$$$$.
Sorry Charlie.

To get back to Bennie's statement, the grounding of all metal is not a function of the neutral at the service, that is one of the purposes of the grounding electrode at the service.

Again, if one is to have a nonmetallic path to a downstream panel from the service, and run two ungrounded conductors and 'another' conductor to be used as an equipment grounding conductor, it can be connected to the service neutral or ground bar and still perform the same function.

If you have the same scenario, only now you run these conductors from a panel that is downstream from the service, the conductor that is not a phase conductor should not be connected to the neutral bar as this could potentially create all kinds of problems. Such as electrical 'noise' on the eqiupment grounding path and dangerous currents.

Pierre
 
Re: Additional Panel

Pierre and Karl: Both of you are correct in your perspective. This subject may be a broken record, dead horse, obsession, or just plain boring to some.

I get personal emails from some who are learning from this topic and from my questioning the accepted practice.

I have no problem with the code section, my concern is the accepted practice of preventing multiple ground paths by reducing the size of the fault path conductor. This is not within the standards of good engineering.

A cable assembly to a panel does not have to be 4 wires to be safer. It is actually more hazardous for the fact of slowing the fault clearing time.

This is regressive engineering and I am sure the code maker's did not intend to do that.
 
Re: Additional Panel

As to your first post, there is nothing wrong with 3 wires to your panel if there are only 240V loads. There will be two “hots” and an equipment grounding conductor. (Live with the fact that you can’t feed 120V from this panel)
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Quote” I have no problem with the code section, my concern is the accepted practice of preventing multiple ground paths by reducing the size of the fault path conductor.“

So re-grounding a neutral at a “subpanel” is good engineering?
_________

Quote ”This is not within the standards of good engineering.”

This is not in line with your standards.
_________

Quote ”A cable assembly to a panel does not have to be 4 wires to be safer. It is actually more hazardous for the fact of slowing the fault clearing time.”

How do you figure that? NEC ground sizing requirements are inadequate?
___________

Quote ”This is regressive engineering and I am sure the code maker's did not intend to do that.”

Your right Bennie, lets run 500MCM to all panels to speed up fault clearing time.

__________

Quote” “I still can not find where the code book states that 4 conductors are required to a panel.”

It does not state it specifically, but if you accept the fact that you need to read and follow these rules, and not make your own, you will come to the conclusion that 4 are required if you serve 120 and 240V loads.

120/240 panel fed from service panel.
You’ll need two “hots” to get 240V
You’ll need a neutral if you want 120V
You’ll need an equipment grounding conductor.
(yes the neutral and ground connect at the same place in the service equipment, but they cannot be connected together at the "subpanel"
Do the math. (hint, I count 4)
 
Re: Additional Panel

I think we are forgetting why the ground electrode conductor is separated from the neutral at a remotely mounted panel.

The only reason is to prevent normal load current from dividing and flowing on the ground conductor. Separation is the best way sometimes in a panel with a metal conduit to the main service.

A continuity break in the metal conduit will perform the same function as obtained by the neutral ground bus separation. This is in full compliance with the NEC, 250.6.1.& 3.
 
Re: Additional Panel

Quote” I think we are forgetting why the ground electrode conductor is separated from the neutral at a remotely mounted panel.”

Really has nothing to do with the GEC
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Quote “The only reason is to prevent normal load current from dividing and flowing on the ground conductor.”

More specifically this is done to limit the voltage to ground on equipment 250.4(A)2.

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Quote “A continuity break in the metal conduit will perform the same function as obtained by the neutral ground bus separation. This is in full compliance with the NEC, 250.6.1.& 3.” (250.6(B)1&3?

No it’s not, you still must comply with 250.4(A)5 and 250.4(B)4 as stated in 250.6(B)
 
Re: Additional Panel

engy,
Quote ?A cable assembly to a panel does not have to be 4 wires to be safer. It is actually more hazardous for the fact of slowing the fault clearing time.?

How do you figure that? NEC ground sizing requirements are inadequate?
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Bennie is correct about this. The EGC is smaller than the grounded conductor and therefore would have a higher impedance. The higher the impedance of the fault clearing path, the longer the fault will exist.
Don
 
Re: Additional Panel

Engy: Why is the MGN from the distribution transformer used to carry ground fault current from the premises wiring system?

A three wire cable assembly will provide a lower impedance path for ground faults. This complies with 250.4.A.5 and 250.4.B.4
 
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