Service Panel - New Construction

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1

Originally Posted By: mpatton
This post was automatically imported from our archived forum.


I had a question asked of me the other day, and sadly I answered it incorrectly “I think” icon_redface.gif


The question "what is the minimum size panel (65, 100, 150, 200 AMP) permitted in new construction?"

Since this question was asked, I though it would be simple to find a "code" source. I have looked and yes I understand that a load calculation has to be performed to asses the proper amperage.

What I am looking for is a code or other quotable source that states something like "if the calculations are below X, the minimum current standard panel is X"

Example the house has gas appliances and is a two bedroom on slab, the requirement is for 65 amp, however the minimum meter and panel requirement for new construction is 100 amp.

I almost fell asleep reading the NEC code and could not find this (not that I could not have missed it, imagine that)
I called the local county inspector and got referred to a state level code enforcement officer that has yet to return my calls.
I have looked at "HUD", formally they would not comment since they are regional now that is out of their jurisdiction to comment.???
I called the local utilities and was referred to a project manager that has yet returned the call.
A local supply house commented that they thought 100 amp was the minimum new service but could not provide any supporting documentation (they did look for it and could not find it either)

Any help would be appreciated, this has become a mission as opposed to just a question.

--
Michael Patton
AA Home Inspection
Serving Northern KY & Greater Cincinnati OH

AA@AAHomeInspection.net
www.AAHomeInspection.net

2

Originally Posted By: Bob Badger
This post was automatically imported from our archived forum.


Quote:
230.79(C) One-Family Dwelling.
For a one-family dwelling, the service disconnecting means shall have a rating of not less than 100 amperes, 3-wire.


If the disconnecting means is a breaker this clearly means the service will be 100 amps.

If the service disconnecting means is a 100 amp fused disconnect any fuse less than 100 amps could be installed.

Does this mean as long as I install a 100 amp disconnecting means I could install 60 amp fuses and conductors to a 60 amp panel?

The handbook says no, but I do not find the code to be clear on this. ![icon_rolleyes.gif](upload://iqxt7ABYC2TEBomNkCmZARIrQr6.gif)

EDIT:

I did some more hunting and found that the code is clear on this.

The following is from the section of article 230 (Services) that deals with service entrance conductors.

Quote:
230.42(B) Specific Installations. In addition to the requirements of 230.42(A), the minimum ampacity for ungrounded conductors for specific installations shall not be less than the rating of the service disconnecting means specified in 230.79(A) through (D).


This is all based on the load being small enough to be carried on a 100 amp service.

In no case are you allowed to provide a service less than the calculated load, common sense but it must be said as some hack contractor would try to provide to small of a service.

--
Bob (AKA iwire)
ECN Discussion Forums
Mike Holt Code Forum
3

Originally Posted By: jpeck
This post was automatically imported from our archived forum.


Bob Badger wrote:
"230.79(C) One-Family Dwelling.[/b]
For a one-family dwelling, the service disconnecting means shall have a rating of not less than 100 amperes, 3-wire."

If the disconnecting means is a breaker this clearly means the service will be 100 amps.

If the service disconnecting means is a 100 amp fused disconnect any fuse less than 100 amps could be installed.


I've read this a couple of times and am not sure I understand what you are saying.

First "230.79(C) One-Family Dwelling.[/b]
For a one-family dwelling, the service disconnecting means shall have a rating of not less than 100 amperes, 3-wire."

Then "If the service disconnecting means is a 100 amp fused disconnect any fuse less than 100 amps could be installed."

The minimum service required to a one-family dwelling unit is 100 amp, as stated in your code quote. That means that the minimum oversurrent protection, fuse or breaker, must also be rated 100 amp minimum, with appropriately sized service entrance and feeder conductors, etc. I am not sure when the 100 amp minimum came into effect, though.

That means that an older home, a much older home, could have a 60 amp service, however, if the service is replaced, the service needs to be 100 amp (at least in areas where the NEC is in effect, and I would apply it to all areas without a code as a nationally accepted minimum safety standard).

--
Jerry Peck
South Florida
4

Originally Posted By: mpatton
This post was automatically imported from our archived forum.


Bob & Jerry,


Thanks for the response, I did read this in the code and somehow glossed over it. Not than any code book is ever going to be easy concise reading but wouldn't it be nice to simply state:

"the minimum service and overcurrent protection is to be 100 amp"

Thanks for the comments, I have been "told" that this statement may not be true when pertaining to "manufactured" homes, any comments?

Again it is great to have good resources available for this type of information, it is amazing how many times I have read and either not comprehended or retained information only to have a conversation and realize the application or lack of it.

Thanks,

--
Michael Patton
AA Home Inspection
Serving Northern KY & Greater Cincinnati OH

AA@AAHomeInspection.net
www.AAHomeInspection.net

5

Originally Posted By: roconnor
This post was automatically imported from our archived forum.


Quote:
(IRC) E3502.1 Rating of Ungrounded Conductors
Ungrounded service conductors shall have an ampacity of not less than the load served. For one-family dwellings, the rating of the ungrounded conductors shall be not less than 100 amperes, 3 wire. For all other installations, the rating of the ungrounded conductors shall be not less than 60 amperes.


--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong