Hello all. Just did my second mock inspection at a manufactured home. The main exterior service panel is rated at 150 amps with breakers adding up to 110 amps. It’s correctly fed with 2/0 aluminum wires. Neutrals and grounds are bonded at this panel. The breakers amperage total is 110 amps.
The interior sub panel is rated at 200 amps with a 200 amp breaker. It’s correctly fed from the main service panel with 4/0 aluminum wires. The neutrals and grounds are correctly not bonded in this sub panel. Adding up all the breakers in the sub panel is 440 amps.
As far as what I’ve learned in their pre-licensing courses this is a no- no.
Am I missing something?? Help would be much appreciated.
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Yes, don’t add up the amp ratings of each breaker in the panel.
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No, adding up the amperage ratings of individual breakers in a panel does not indicate the panel’s total capacity. The panel’s capacity is determined by its main breaker or the upstream electrical service, and it’s designed to handle a certain maximum load, not the sum of all individual circuits.
Here’s why:
- Panel Capacity:
The panel’s capacity is determined by its main breaker (or the service entrance breaker), which limits the total amount of current that can flow into the panel according to a home improvement forum.
- Individual Breakers:
Individual breakers are sized to protect the wiring of specific circuits. They trip if the current draw on that circuit exceeds their rating.
- Load Calculation:
The total amperage of all individual breakers can easily exceed the panel’s capacity because it’s assumed that not all circuits will be running at maximum capacity simultaneously.
- Example:
A 200-amp panel may have individual breakers that add up to 300 or even 400 amps, but the panel is still limited to 200 amps by the main breaker, according to a Reddit thread.
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As Kevin said, don’t add up the breakers. Would you mind sharing the section or text in their pre-licensing course that advises you to add up the breakers? Let’s take a look at what it says. BTW, who is their?
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This 
You need to look at what the panel is rated for, the info will be on the label inside the panel somewhere, and if the feeders & disconnect for that panel is in line with the manufacturer’s rating..
if the breaker/disconnect at the service panel is rated less than the sub panel’s main breaker/disconnect, the sub would have plenty of over current protection anyway so it shouldn’t be an issue.
Maybe @rmeier2 can explain it better…
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The total of all of the amp ratings of all of the circuit breakers is basically meaningless and cannot be used to determine if the service is properly sized. A load calculation is required to determine the minimum size of a service which is beyond the scope of a home inspection.
Is there a circuit breaker in the service for the sub-panel feeder?
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The main service panel has 150 amp main breaker. The sub panel has a 200 amp main breaker.
Thanks Kevin,
I’m at the end of the internachi training and my brain is overloaded. As soon as I read your response I remember learning about that. That’s what mocked inspections are about to get some of the kinks out.
Thanks a million!
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Their …was a typo. As I stated in another response my brain is in overload from all the training. I’m not sure where adding up all the breakers came from but it’s been deleted from the gray matter.
It’s encouraging to know there’s help when needed. Thanks to all!
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Hey Robert,
The forum has helped me realize my goof. Thanks for the reply!
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Just realize regardless of the #4/0 feeder conductor size or the 200 amp OCPD in that sub-panel that the sub-panel has a capacity no larger than the 150 amp service disconnect.
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Hi Thomas
Adding the total of all breaker ratings is totally wrong. Service mains are sized using a calculation set forth by the NEC. Most of the circuits are derated due to the fact that all circuits in the home will not be on at the same time at 100% rating. I would encourage you to review appendix D of the NEC (Calculation examples for single family homes).
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