Main breakers in sub panels

[RICHARD R. GREEN]

Need some clarification on sub panel breakers and possible undersized wires.

The 200 amp main service supplied a sub panel from a 40 amp breaker using #8 AWG. This # 8 AWG wire was connected to a 100 amp main breaker in the sub panel. Is this a situation where you would report an undersized wire attached to the 100 amp breaker or is it redundant as the 40 amp breaker in the main panel should prevent more the 40 amps running through the #8 AWG wire? If you need clarification please ask.

Awaiting your responses. Thanks all.

[Paul W. Abernathy]

If it is within the same building then the 100A breaker at the remote distribution panel is simply a disconnect, In fact, it is not actually required but in many cases it is cheaper than a MLO panel so they install it. The conductors and panel are protected by the 40A OCPD at the source.

[Robert Meier]

There could be a possible problem is if the 100 amp CB is not listed for use with a small #8 conductor.

[RICHARD R. GREEN]

Thank you Paul, that is what I thought but needed to be sure. Thanks to you also Robert.

[Robert J. OConnor]

Originally Posted by Robert Meier

There could be a possible problem is if the 100 amp CB is not listed for use with a small #8 conductor.

Good point ... but how significant that is for an HI is another story ...

[Robert Meier]

Originally Posted by roconnor

Good point ... but how significant that is for an HI is another story ...

I'm not one so I cannot answer that. But given all that I've read on this forum about HI's doing IR scans I would think that the use of the proper termination that matches the conductor size is somewhat important.

[Christopher Currins]

Originally Posted by Robert Meier

I'm not one so I cannot answer that. But given all that I've read on this forum about HI's doing IR scans I would think that the use of the proper termination that matches the conductor size is somewhat important.

It is.

[Robert J. OConnor]

The only thing I can see as being an issue is if the smaller wire is completely on one side of a large lug where a somewhat poor connection is possible.

I would make a note of the condition and check that it looks like a solid connection, but I just don't see it a being a significant issue unless it was poorly installed.

JMO & 2-Nickels ...

[Robert Meier]

So if the 100 amp CB is clearly labeled as suitable for use with #6-#1/0 conductors you don't see a problem with connecting a #8?

[Robert J. OConnor]

Originally Posted by Robert Meier

So if the 100 amp CB is clearly labeled as suitable for use with #6-#1/0 conductors you don't see a problem with connecting a #8?

Things are not always that black or white for home inspectors ... there are different shades of grey.

I indicated I would make a note of that as an issue. But if there is a solid connection, why would you consider that a significant issue or safety hazard (which for an HI would mean an immediate correction recommendation)?

[Robert Meier]

Originally Posted by roconnor

Things are not always that black or white for home inspectors ... there are different shades of grey.

I indicated I would make a note of that as an issue. But if there is a solid connection, why would you consider that a significant issue or safety hazard (which for an HI would mean an immediate correction recommendation)?

Well there's right and wrong according to the listing of the equipment. I've seen double taps that have been in panels for 20 years without any problems. Should a HI not report those either because they look good or have been there for a long time? Where do you draw the line?

[Robert J. OConnor]

Originally Posted by Robert Meier

Well there's right and wrong according to the listing of the equipment.

Thats the black and white for electricians and AHJ's ... HI's often have to make judgment calls as to how significant an issue is. I agree a small wire on a large breaker is likely an issue with the listing. I just don't agree it's a significant issue if there's a solid connection.

Originally Posted by Robert Meier

I've seen double taps that have been in panels for 20 years without any problems. Should a HI not report those either because they look good or have been there for a long time?

How about a smaller wire on a larger breaker with a poor connection (say to one side of the lug) thats been there for 20 years without a problem. I would consider that a significant issue, because loads on circuits can change, and just like double lugs with wire-to-wire contact, there is a potential for a poor connection.

Originally Posted by Robert Meier

Where do you draw the line?

Thats a difficult call for HI's on some issues.

[Paul W. Abernathy]

Originally Posted by Robert Meier

So if the 100 amp CB is clearly labeled as suitable for use with #6-#1/0 conductors you don't see a problem with connecting a #8?

Would be a listing violation. Being that I can't see the breaker....I will leave that to the origional poster.

[Robert Meier]

Originally Posted by pabernathy

Would be a listing violation. Being that I can't see the breaker....I will leave that to the original poster.

Yup, that was my point it could be. I'm assuming that an HI should note that in his report, yes or no?

[Chiun D. Ng]

Do you have pictures for the panel you inspected?