Main disconnect question

Main disconnect is at the exterior meter box and labeled as 100 amp. Panel has a disconnect labeled at 70 amp with #2 copper SEC. I guess my question is why would one want to have a smaller rated breaker at the panel? Wouldn’t it be better to have 100 amp breakers at both locations? Is this an issue? House was built in 1940, so this is an upgrade, but not sure when it was done, seller does not know either, said it existed when he bought the house.

The ’ panel’ is now a sub panel and should be wired as such since the main disconnect is at the meter location. What is the wire size coming into the sub panel. If more than what is rated for a 70 amp breaker, then you will be blowing that 70 amp breaker maybe. The panel rating is the weakest link. 70 amp max is all the sub panel can handle - even if the wire is larger and rated for 100 amps. The 70 amp breaker is the weakest link , aka a 70 amp service. Advise them if this concept and upgrade breaker to a 100 amp - if the wire is sized correctly

Opps. Just noticed you said #2 copper SEC. Breaker at sub panel is definitely undersized then

That’s not correct. The #2 copper SEC is protected by the 100 amp breaker at meter. The 70 amp breaker is protecting everything downstream.

Won’t the #2 conductor be feeding 100 amps to the 70 amp breaker? The #2 runs from the meter, where the main disconnect resides, to the 70 amp breaker in the panel. I also don’t think I have enough info since I have no access to the interior of the meter. Bond is also present in the panel; which is incorrect if tthis really is an RDP.

A few photo’s might help. :slight_smile:

One comment, the SEC’s end at the 100 main disconnect, the conductors from the 100 amp main to the 70 amp CB are feeder conductors. Before you recommend upgrading the 70 amp CB you would need to know the rating of the subpanel.

Sub is rated at 125 amp. Won’t the feeders to the 70 amp CB allow 100 amp to flow to the 70 CB? I dont have access to the 100 amp since it is in the meter box and I don’t remove those. Anyway I referred them to an electrician since I think 70 amp is not enough. I am just curious about how many amps are flowing to the 70 CB. But, it’s no different than the 15amp breakers that are supplied by the 70 CB.

Yes you are correct. Thank for correcting me and clarifying that

Theoretically you cannot have more than 70 amps flowing between the 100 and 70 amp CB’s because all of the loads are on the load side of the 70 which is the limiting factor.

The 100 amp breaker does not cause any load to flow. The actual loads are what places the load on the feeder.

What basis was used to make someone feel that 70 amps was not enough? Were issues stated that the breaker was tripping or just a nebulous feeling?

In the Chicago area, less than 100 amps is considered less than adequate and most jurisdictions don’t allow less than 100 amps.

If you didn’t have access how did you determine it’s a 100 amp breaker (disconnect)? The service (Main) disconnect should be accessible.

As Jim mentioned power does not “flow” to the breaker. Electricity doesn’t flow all by itself, it needs a load demanding electricity.

The disconnect at the meter is labeled 100 amp. But I don’t open meters

There should be no need to open a meter. They are the property of the power company and some consider opening one a criminal act.

Exactly why I didn’t have access, I can only read what the breaker is rated.