Undersized service wire

[Sean Fogarty]

I looked at a home today that was 15 years old. 200 amp service with 2/0 alum from the meter to the panel. I know it is not allowed now, but was it then? I wrote it up as not being up to currant standards, but an electrician should be consulted for proper application.

[rmaday]

It's 150 amp service.

Take the lowest of Meter, SEC, Panel rating, main disco.

What is not allowed now?
What was it that you wrote up as to not being to current standards?

[Sean Fogarty]

I thought the possibility of using an udersized wire in between the meter and the panel. If it had 150 amp service why the 200 amp box? I understand the whole principle of the lowest, but if everything was 200 then wouldnt the smaller wire be incorrect? Or if the sec was 150 why would you use a 200 amp panel?

[wsiegel]

Because that is what they bought. See that all the time. Also allows them to increase service later if the want to.

[rmaday]

Was the main disco 200?

[Mark E. Northrup]

Sean your a little confusing. Is the main disconnect 200 amp and the wire 2/0 Alum.
The panel can be bigger but not smaller.
If the wire is rated for a 150 amp breaker and a 200 amp is installed this is incorrect.
Hope this helps

[Sean Fogarty]

Yes The main panel and the breaker were 200 amps. It was an outside panel. The meter base was directly above it and the wire that connected both was rated for 150 amps. Hope this clairifies things.

[psullivan]

Since the disconnect is larger (200A) than the safe carrying capacity of the service entrance cable (i.e., 2/0 AL = 150A), then this is (and always has been) a problem. If the home's electrical components draw more than 150A of current, then the main disconnect breaker will allow it (until it reaches 200A), and the service entrance cable will heat up because it is undersized. Here's how I would write it up:

The service entrance cable is composed of AWG 2/0 Aluminum, and is capable of safely carrying 150 Amps of current. However, the main disconnect circuit breaker is rated at 200 Amps, and is not therefore not compatible with the service entrance cable. Recommend a qualified electrician evaluate and determine a course of corrective action for electrical safety.

Hope this helps ... Good Luck ...

Peter Sullivan
National Property Inspections
Round Rock, TX

[Ed Padilla]

Excellent info Peter. Thanks for sharing.

[rmaday]

Ask yourself these two questions...

What is the overcurrent protection for the ciurrent coming into the panel?

What is the overcurrent protection for the SEC?

[Sean Fogarty]

Here is what I wonder. Almost every house I look at, the sec from the transformer is always smaller until it gets to where it is clamped together in front of the weaterhead. The wire from the clamps to the meter are usualy the right size but not the sec. Is that not the power companies responsibility? Some of the older home I know the copper wire coming in is solid. Would solid copper be thinner than stranded with the same gauge?
Also why is the neutral wire sometimes smaller than the two hot feeds? Should it not be the same size.

[James E. Braun, CMI]

Originally Posted by sfogarty

Here is what I wonder. Almost every house I look at, the sec from the transformer is always smaller until it gets to where it is clamped together in front of the weaterhead. The wire from the clamps to the meter are usually the right size but not the sec. Is that not the power companies responsibility? Some of the older home I know the copper wire coming in is solid. Would solid copper be thinner than stranded with the same gauge?
Also why is the neutral wire sometimes smaller than the two hot feeds? Should it not be the same size.

If all your questions deal with the wire coming from the pole. Then the wires can be smaller because they claim these wires get more air movement around these wires thus keeping them from over heating. Kinda makes sense when you think about it. Also the SEC wire should have a smaller feed back to the transformer than wires feeding to the house thus that is why it is smaller.