Electrical panel install wire question

[hoosierdoc]

I'm starting new service and have a 125a panel mounted next to the 200a meter base. I have 1/0 aluminum wire which is I think rated for 125a but am told "feeder only rated for 100amp" by the inspector.

do I need wires to handle 200a since that's the meter rating even though panel only 125a? I should add I bought a panel without a disconnect breaker so maybe that's why?

 

[Fargo]

I'm starting new service and have a 125a panel mounted next to the 200a meter base. I have 1/0 aluminum wire which is I think rated for 125a but am told "feeder only rated for 100amp" by the inspector.

do I need wires to handle 200a since that's the meter rating even though panel only 125a? I should add I bought a panel without a disconnect breaker so maybe that's why?

If you bought a main lug panel versus a main breaker panel for a new service, I don't believe it will work as a direct hookup. If memory serves, a main lug panel is only allowed as a subpanel running off a main breaker in the main panel. Your hundred amp rated wire needs to be protected by a 100 amp breaker of some sort.

 

[hoosierdoc]

If you bought a main lug panel versus a main breaker panel for a new service, I don't believe it will work as a direct hookup. If memory serves, a main lug panel is only allowed as a subpanel running off a main breaker in the main panel. Your hundred amp rated wire needs to be protected by a 100 amp breaker of some sort.

That's I wondered. REMC said they'd sign off on it. The zoning guy only commented on the feeder wire size, not lack of breaker. My contractor is fine using this as a main panel. Safety suggests a disconnect though. Reading online it says many contractors won't bother with the main breaker.

hoping to hear back tomorrow from inspector. The frustrating thing is Monday at 2:30 was inspection time. I called county at 4p and they said I passed, but I said I never saw the inspector. Then Tuesday REMC came out and signed off. Then I added a 30a double pole breaker today and saw the paper containing the deficiency dated 4/24 that was not there 4/25

 

[Fargo]

What does the deficiency paper say? I don't see there being a way that you can run a non-main breaker 125 amp panel with 100 amp service feeder and have it be code but then again I'm not an electrician.

 

[hoosierdoc]

What do you mean by a "100 amp service feeder"? I am much further from electrician than you

200a meter base, main panel can handle 125a. I have 1/0 aluminum wire running 24" between lugs. My online research says that should be kosher but apparently it's not

 

[Fargo]

What do you mean by a "100 amp service feeder"? I am much further from electrician than you

200a meter base, main panel can handle 125a. I have 1/0 aluminum wire running 24" between lugs. My online research says that should be kosher but apparently it's not

100 amp service feeder means the wire you are using to feed your main panel. I see three large problems here.

The first is that you have a panel rated to pull 125 A but apparently the wire you have feeding it is only rated for 100.

The second is that you have a 200 amp service with 100 amp rated wire and no 100 amp protection up or downstream.

Depending on what all you have in the panel, a short could pull 200A through 100 amp rated wire and a 125 amp rated box which would not end well. Even without a short, If you pulled the panels amp rating through it you would still be overloading your wires which are apparently derated by the code down to 100 A if used as service feeder.

By my calculation, you need the box to have a 100 amp main breaker in it. That will prevent you from pulling more than 100 A through that wire. That said, I would confirm that with an electrician as I am not certain that only downstream protection will meet the code.

 

[hoosierdoc]

I think the easiest fix is get a 100a panel with a main breaker and be done with it. I can then use this panel as a subpanel inside my out building when it's up.

i see your point on over amp draw overloading the feeder wires. But I'll go to my grave saying numerous online electrical utility pages state 1/0 aluminum is rated for 125a amp

 

[Fargo]

I think the easiest fix is get a 100a panel with a main breaker and be done with it. I can then use this panel as a subpanel inside my out building when it's up.

i see your point on over amp draw overloading the feeder wires. But I'll go to my grave saying numerous online electrical utility pages state 1/0 aluminum is rated for 125a amp

Oh, I'm sure it is normally rated for that. The problem is that the national electrical code has certain applications when a wire is derated down from it's standard rating. Apparently the inspector believes that yours is one of those applications.

 

[Fargo]

If memory serves, some main lug panels can be converted to main breaker panels. If yours is already installed it might be worthwhile to look into whether you can just convert it over with a 100 amp main breaker. You would need to ask someone more knowledgeable than myself though.

 

[Cameramonkey]

Also remember aluminum wire does not handle the same amps as equal gauge copper.

Thats it for my expertise. I'm spent.

 

[hoosierdoc]

Also remember aluminum wire does not handle the same amps as equal gauge copper.

Thats it for my expertise. I'm spent.

i could have done smaller copper, but $$$

 

[Cameramonkey]

i could have done smaller copper, but $$$

I hear ya. I had to make that same call when I was replacing my panel. old copper was 2" too short for the new main. And the cost was nearly double to do copper.

 

[sljccj]

I think hed going by 80% load rating.
you ran wire that can handle 125amps 80% is 100amps
he didnt derate the wire. He is saying its approved usage is 100 amps based on 80% load.

When I pull #12 wire fot a 120v circuit, I install a 20 amp breaker. I need to be sure that the equipment being plugged in will not continuously exceed 16 amps or 80%


im not a certified electrician. I am an industrial maintenance tech.
I do a lot of electrical work Set panels. Run conduit pull wires etc. we always plan circuits using the 80% load factor.

this explains it better than I can

http://m.ecmweb.com/basics/sizing-circuit-breaker

 

[nra4ever]

Pull all new copper. Don't go cheap on your electrical. Dump that aluminum.

 

[hoosierdoc]

That makes sense, thanks.

I think hed going by 80% load rating.
you ran wire that can handle 125amps 80% is 100amps
he didnt derate the wire. He is saying its approved usage is 100 amps based on 80% load.

When I pull #12 wire fot a 120v circuit, I install a 20 amp breaker. I need to be sure that the equipment being plugged in will not continuously exceed 16 amps or 80%


im not a certified electrician. I am an industrial maintenance tech.
I do a lot of electrical work Set panels. Run conduit pull wires etc. we always plan circuits using the 80% load factor.

this explains it better than I can

Sizing a Circuit Breaker

 

[hoosierdoc]

Pull all new copper. Don't go cheap on your electrical. Dump that aluminum.

No thanks

 

[CountryBoy19]

There are 2 things at work and they don't always align. NEC & local code/ordnance/inspector preference.

IIRC, NEC allows for service entrance (your 24" long 1/0 wires) to be sized according to the expected load no matter what the panel size is. IE, you could install a 400 Amp panel on 200 amp service where you expect total load for the panel to be 50 amps and you would be kosher to use a 50 amp cable (as long as you account for derating etc) in accordance with NEC. That being said, you will NEVER find an inspector that actually understands that part of NEC, will perform the calculations, and give you a thumbs up, they will want to see 200 amp cable to cover their butt.

I have no idea how main lug vs main-breaker plays a role in the above. Considering that IAW NEC you size the wire to the load not the panel rating I'm not sure you would actually need over-current protection for a service entrance cable.

 

[sljccj]

Pull all new copper. Don't go cheap on your electrical. Dump that aluminum.

Aluminum wire is ok. Rule of thumb is use double the size of what the recommended copper wire is.

 

[Fargo]

I think hed going by 80% load rating.
you ran wire that can handle 125amps 80% is 100amps
he didnt derate the wire. He is saying its approved usage is 100 amps based on 80% load.

When I pull #12 wire fot a 120v circuit, I install a 20 amp breaker. I need to be sure that the equipment being plugged in will not continuously exceed 16 amps or 80%


im not a certified electrician. I am an industrial maintenance tech.
I do a lot of electrical work Set panels. Run conduit pull wires etc. we always plan circuits using the 80% load factor.

this explains it better than I can

Sizing a Circuit Breaker

From what I've read, since it is non-dwelling and going in to a 14 to 1 AWG box you have to use the 60 degrees C rating which is 100A for 1/0 aluminum. The 125 rating is for dwelling install.

http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheetOEM46

 

[nate77]

A 200 amp meter base can handle up to a 200 amp main panel, your 125 amp panel wont even make it break a sweat.

As for the main disconnect, it is nice, but not mandatory; I don't have a main on my barn service, and Duke Energy didn't have a problem with it.

If your inspector, and utility are good with what you have, I'd go with it.