Service panel undersized?

This is a two part question:

  1. There is one service panel and one sub panel. According to the labels, both panels are rated at 125 amps maximum. The service panel has one 100 amp breaker (common int trip) and one double pole 40 amp. The sum of all the breakers in the subpanel exceeds 300 amps. Am I missing something and should I call both of these out as undersized.

  2. My reporting software has a rec for service “substantially” less than 200 amps to be upgraded. What is the opinion out there for making this rec in this case? The two wires from the 100 amp breaker to the sub are 1 AWG AL; I could not read the rest but the SEC looked like 1/0 AL

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#1 Al is rated for 100 amps at 75° C. Adding up the CB’s is a waste of time and is not indicative as to the service being of adequate size.

I don’t call out 100 amp panels. Older homes have them all the time and they are more than enough unless all the equipment is electric.

  1. Never “add up” the breakers. Not only does this do nothing in determining the potential, it makes you look foolish (not saying you’re foolish, just that it looks that way) to professionals who know better.

  2. Never rely on your “reporting software” to give you proper direction for reporting an actual defect. In and of itself, a 100 amp service is not a defect.

My question;

I hear this more and more often to “add up breakers” in the panel to see if it’s overloaded. Is this something that’s actually being taught by a training course? If so, you’re getting training from the wrong place.

Sorry for sounding foolish, but for someone without an electrical background and who normally has someone else inspect the electrical system it is not immediately clear what the panel rating refers to. I’ve been through the Nachi course and I don’t remember it covering panel ratings other than saying that it is one of the limiting factors.

I would still like a explanation(and I will use layman’s terms) on why this 3 wire service which has two hot wires each large enough to supply 100amps is not more than the panel rating at 125 amps. Doesn’t 100 + 100 = 200?

If not called a defect, shouldn’t it be mentioned in the report that the 100 amp service may need to be upgraded if all electric equipment is installed? ( The furnace and hot water heater are both NG and the hot water heater needs replacing)

In order to see if the panel is to small one would do a service calculation. To do this calculation one would use the size of the appliances attached not adding the size of the breakers.

It hasn’t been to long ago (less than three years) that I wired a 2800 square foot house using a 125 amp panel. The heat, water heater and range was all gas.

Some inspectors make those statements as a courtesy but personally I think it isn’t necessary and depending on what you say it could increase your liability. IMO

Again, I wasn’t targeting you specifically. I’ve been hearing this statement quite often lately and it has me concerned that it might be included in some “training” curriculum. Sounding “foolish” here (on this board) is par for the course for many, but if you’re passing on this information to a paying client, a refund may be in order.

The panel ratings are listed to show the limits of the equipment. The service capacity is determined by the smallest rated component within the equipment. In your picture, the #1 conductors look like CU to me, not AL. In which case, I would list this as a 125A service.

You might be correct. Since there are two service disconnects (100 and 40 amp) the service rating is less clear.

The left looks like copper, the right looks like aluminum. They are sized larger than the feeds coming off the 100amp disconnect so perhaps they are Al.

It’s unfortunate that once again we have “reporting software” determining what the client is told.

I would suggest that if you do not know why a comment is the reporting software and when it applies it is best not to use it.

This has been a recurring theme of late and it is making all of us look a bit silly.

Please do not rely on the comments of your reporting software to get it right.

I see the AL now - the one’s connected to the 100A breaker. That means the CU conductors to the left are much larger than #1, in which case, I still call this a 125A service based on the panel rating.

I put this in my report if questioned about service size or if it is enough.
Load testing is beyond the scope of a general home inspection. A competent electrician spending considerable time on load calculations would be able to determine this. The home appears to be functioning well with the service provided and the appliances installed however if numerous changes or an out building were to be installed you may wish to speak with a competent electrician at that point.

You need to calculate the demand load to determine the proper service size. Don’t add the values of the individual breakers together. If you don’t know how to calculate the demand, download my free Residential Electrical Service Size Calculator. The calculator will tell you the correct service rating, conduit size and service conductor sizes for both copper and aluminum.

I suggest that you delete that comment from your inspection report software.

Doing load calculations is outside the scope of a home inspection but the calculations can be done in only a few minutes. I advise inspectors to use my Residential Electrical Service Size Calculator only for their own edification. The calculator is a scaled down version of a calculator that I had originally created for electricians.

Yes George that program I have never had to use but it does help to understand loads implied. As for the comment on the report yes removed ASAP.
The only time someone would need that kind of load is maybe with Electric Heat or they decide to add a garage with electric welding equipment ect.

Just inform them that the “estimated” amperage is 125 amps. Job done.

P.S. If it’s 100 amps, I have a statement that informs them that the house just meets today’s minimum amperage requirements and suggests that they speak with a parky about the limitations of the service.