I have a customer who is trying to sell a home that has a 200A service panel being supplied by 2 AWG aluminum conductors. A home inspector for the buyers discovered this and of course wants it rectified. I told him we would need 4/0 aluminum and gave him the cost to do the job. He asked me if I could just replace the 200A main breaker with a 100A breaker. The house is about 1200 sq ft with no basement and the load could be served by a 100A service. I can not find anything in article 230 that would prohibit this. Just replacing the breaker would be a lot less expensive for him as the path from the meter to the main breaker box will require some work. I don't see the 100A breaker as a code violation but thought I would ask here to get some opinions.
100A main breaker on a 200A service panel.
- Thread starter trojans4
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Not a problem if the load calc works. Are you installing a branch type 100A breaker and back feeding it? If so, you'll need a breaker hold down. You could even leave the old 200A breaker as a feed through as long as it isn't labeled LINE and LOAD.
kwired
Electron manager
- Location
- NE Nebraska
I agree with that reply.
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
Please explain this as I'm not seeing what you're talking about. Not the
"line/load" part, but the feed through part.
John120/240
Senior Member
- Location
- Olathe, Kansas
Feed the panel with a back fed 100A as stated. With a hold down kit. Then the 200A breaker could be used to feed a sub panel if so desired. Granted you only have a 100A service so 100A is all the 200A will ever see. Maybe not a common installation but nothing inherently wrong with it.
John120/240
Senior Member
- Location
- Olathe, Kansas
I imagine using a 100A two pole breaker. Are 100A mains interchangeable with 200A mains ? I do not know.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
The OP said that the building could be served by a 100A service, not that the POCO thinks that it IS a 100A service.
In some areas, notably LADWP, the POCO will not allow the service size to be smaller than the nominal rating of the panel even though the installed main breaker is smaller.
If there was not any upstream protection for the service wires lower than 200A, it is a little surprising that POCO allowed the service to be connected in the first place.
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In some areas, notably LADWP, the POCO will not allow the service size to be smaller than the nominal rating of the panel even though the installed main breaker is smaller.
If there was not any upstream protection for the service wires lower than 200A, it is a little surprising that POCO allowed the service to be connected in the first place.
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curt swartz
Electrical Contractor - San Jose, CA
- Location
- San Jose, CA
- Occupation
- Electrical Contractor
No, the 200 amps would be the maximum size. There is nothing wrong with replacing the breaker with a smaller breaker. The suggestion was to actually leave the 200 amp main unused and add a 100 amp back fed breaker in the panel. The is also acceptable assuming you can get the appropriate hold down kit.
kwired
Electron manager
- Location
- NE Nebraska
You will no longer have what is marked on the label, I don't know that equates to any violation though. Many panels that come with main lugs are "convertible" meaning you can put any size main designed to fit them as long as you don't exceed the current rating of the panel with overcurrent protection - which is generally hard to do. Take Square D QO and Homeline series - both use the same main breaker assemblies in two frame sizes 125 amp max and 225 amp max. If you have a main lug panel chances are the bus is rated either 125 or 225, and it is not all that possible to install too large of a main breaker for the bus. I do believe you can get a 100 amp breaker in the 225 frame as well, but are not going to find anything over 125 in the 125 frame. Now purchasing a 225 amp bus panel and a separate main is usually going to cost more than the packaged panels with a main already installed and this just doesn't happen all that much either.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
If there is a listed 100 amp replacement for the 200 amp main then no violation.
talked to the inspector
talked to the inspector
Thanks for the replies. I talked to the AHJ and he said he would not approve it unless I could confirm the 100A breaker was listed for use in the 200A panel. He didn't think it would be. It is a QO 200A panel. First, no one in my immediate area had a 100A QO main breaker and on further inspection the two breakers are different size physically and it looks like it would not fit anyway. I did email Schneider Electric, who bought out Square D several years ago, to ask about the listing but so far have not received a response. So anyway, I am running 4/0 Al instead.
talked to the inspector
Thanks for the replies. I talked to the AHJ and he said he would not approve it unless I could confirm the 100A breaker was listed for use in the 200A panel. He didn't think it would be. It is a QO 200A panel. First, no one in my immediate area had a 100A QO main breaker and on further inspection the two breakers are different size physically and it looks like it would not fit anyway. I did email Schneider Electric, who bought out Square D several years ago, to ask about the listing but so far have not received a response. So anyway, I am running 4/0 Al instead.
growler
Senior Member
- Location
- Atlanta,GA
The problem is that when you upgrade any part of the service they often want everything brought up to code.
If it's very far from the meter to the panel they may insist on an outside disconnect or meter/main.
If it's a meter/main then the feeder to the panel must be SER and the neutrals and ground seperated.
What about the size of the GEC. If they were useing #2 AL they were probably set up for a 100 AMP service.
When it comes to cost you can get pretty close to a service change. Find out what you will need to do before giving a price.
If they are looking for cheap it may be faster & cheaper to install a 100 AMP panel.
John120/240
Senior Member
- Location
- Olathe, Kansas
A QO 2 pole 100 A would be listed for use in your QO panel. Be sure you use a hold down kit. To the SQ D gurus:
Is performance comprised or are there any objections to using a QO 2 pole 100 A vs a QO 100 A main ?
K8MHZ
Senior Member
- Occupation
- Electrician
But will it be listed for use as a service disconnect?
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Do circuit breakers have a separate listing requirement when used in a panelboard as a service disconnect?
GerryB
Senior Member
- Location
- woodbridge, ct. USA
Don't get it. Is it a 200 amp meter socket? If not you have to change it. The riser is 2" and 4/0? Like growler said what about the grounding.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
It is acceptable.
The part number for a direct replacement Square D 200A frame breaker with a 100A trip is QOM2100VH.
And of course the back-fed breaker method would also work.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Does the back fed breaker need to meet any special properties other than high enough AIC to be used as the service disconnect?
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