Thread: 100 amp service wires used for a 200 amp panel ?

I know this is wrong, but just want to hear from you guys. The service panel is rated for 200 amp, but the service wires were small. I think the service wires were rated for 100 amp 2 AWG, I took a picture of the round meter base, but forgot to actually look at the meter for the 100 amp label.

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Originally Posted by Sam Morris

I know this is wrong, but just want to hear from you guys. The service panel is rated for 200 amp, but the service wires were small. I think the service wires were rated for 100 amp 2 AWG, I took a picture of the round meter base, but forgot to actually look at the meter for the 100 amp label.

Sam, are you sure the wires are not tinned copper?

Originally Posted by Vern Heiler

Sam, are you sure the wires are not tinned copper?

Aluminum clad copper, not the same think ? Aluminum

Originally Posted by Sam Morris

Aluminum clad copper, not the same think ? Aluminum

Tinned or clad, copper is copper!

Originally Posted by Vern Heiler

Sam, are you sure the wires are not tinned copper?

May have been, the wires where small 2/0 I think. Not thick enough for 200 amp

Originally Posted by Sam Morris

May have been, the wires where small 2/0 I think. Not thick enough for 200 amp

2/0 copper service is good for 200amp

Originally Posted by Vern Heiler

2/0 copper service is good for 200amp

Minimum conductor size for 200 amp service is 3/0 Awg CU and 4/0 for AL ?

Originally Posted by Sam Morris

Minimum conductor size for 200 amp service is 3/0 Awg CU and 4/0 for AL ?

Just checked my "Code Check" to make sure. 2/0 copper is listed for 200 amps

Originally Posted by Vern Heiler

Just checked my "Code Check" to make sure. 2/0 copper is listed for 200 amps

Stand corrected, looking at the wrong side THANK YOU

The rating of a panel is the maximum ampacity it can be used with. Using a 200 amp panel and feeding it with 100 amps is perfectly acceptable as long as the OCP is properly rated.

Originally Posted by Jim Port

The rating of a panel is the maximum ampacity it can be used with. Using a 200 amp panel and feeding it with 100 amps is perfectly acceptable as long as the OCP is properly rated.

Yes, but ... the photo shows a 200 amp disconnect - however, the tinned copper conductors are probably 200 amp rated.

That said, though, tinned copper indicates (and it looks like) rubber insulation, and the rubber insulation is quite likely dried out and deteriorated, which can lead to ground-fault leakage and worse.

So what you're saying is I can have 100 amp rated service wires connected to a 200 amp rated panel and that would be acceptable?

Originally Posted by Sam Morris

So what you're saying is I can have 100 amp rated service wires connected to a 200 amp rated panel and that would be acceptable?

IF ... if the disconnect in the panel was 100 amp rated.

The disconnect rating *must not be rated higher than* the rating of the panel mains or the rating of the service entrance conductors.

If someone comes along later and replaces the disconnect with one which has a rating higher than the panel rating or the rating of the conductors ... well ... that person just created a problem which did not exist before.

Originally Posted by Jerry Peck

IF ... if the disconnect in the panel was 100 amp rated.

The disconnect rating *must not be rated higher than* the rating of the panel mains or the rating of the service entrance conductors.

If someone comes along later and replaces the disconnect with one which has a rating higher than the panel rating or the rating of the conductors ... well ... that person just created a problem which did not exist before.

Doesn't the meter base look like its rated for 100 amp, I will be going back tomorrow to check the rating on it, wouldn't that also matter ?. The service wires to the electrical where small 2/0 , they look big in the pictures.

Why do you think a 100 amp feed cannot supply a panel rated for a higher ampacity? You could feed 60 amps into a 200 amp panel if the loads were below the feeder rating.

Originally Posted by Sam Morris

Doesn't the meter base look like its rated for 100 amp, I will be going back tomorrow to check the rating on it, wouldn't that also matter ?. The service wires to the electrical where small 2/0 , they look big in the pictures.

Yes, the meter base rating does matter; for two reasons. They are rated for maximum amperage capacity along with space for the conductors. The meter base should be upgraded to match the service.

The use of 2/0 CU, & 4/0 AL, for a 200A residential service has to meet certain criteria to be allowed to undersize the conductors & the table allowing it was removed in the 2014 NEC, now (where the 2014 NEC has been adopted) it has to be done a little bit differently.

Originally Posted by Rollie Meyers

The use of 2/0 CU, & 4/0 AL, for a 200A residential service has to meet certain criteria to be allowed to undersize the conductors & the table allowing it was removed in the 2014 NEC, now (where the 2014 NEC has been adopted) it has to be done a little bit differently.

Many electrical contractors/electricians tried to apply that table to other-than-dwelling units and had to resize the conductors they had pulled in, which meant resizing the raceway as well.

With that table gone in the 2014 NEC ... all those conductor sizes everyone has remembered for years and years will no longer be applicable - they will need calculations done to justify any reduction from Table 310.16.

It will throw a wrench in the works for home inspectors with that table gone.

Originally Posted by Jerry Peck

Many electrical contractors/electricians tried to apply that table to other-than-dwelling units and had to resize the conductors they had pulled in, which meant resizing the raceway as well.

With that table gone in the 2014 NEC ... all those conductor sizes everyone has remembered for years and years will no longer be applicable - they will need calculations done to justify any reduction from Table 310.16.

It will throw a wrench in the works for home inspectors with that table gone.

You can still use the reduced size conductors in a residence under the 2014 NEC, just going to have to do calculations to prove it.

Originally Posted by Rollie Meyers

You can still use the reduced size conductors in a residence under the 2014 NEC, just going to have to do calculations to prove it.

"have to do calculations to prove it"

That is what I was referring to - many contractors (most, if not all), and most (if not all) home inspectors, went by the table ... which will not be there.

That means that there is not 'quick and easy' 'looksee' to determine the rating of the service based on conductor size.

Now it will be the main service disconnect rating, and then checking to see if the conductors match that rating and ... oops - the table is gone ... what is the rating of those smaller conductors now?

Will not be as easy as it was looking at the table.

Originally Posted by Kevin Wood

It is a 200 amp Main Breaker. So the service must match. #2/0 is fine here too.

Here, with that table no longer in the code, and without calculations, might need 3/0 copper.