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Old 08-28-2011, 01:10 PM   #1
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125 amp rated breaker panel yet I have 155 amps worth of breakers???


Can someone please help me understand this.

When I purchased the house (built in 1905) it still had knob & tube & screw in fuses.

I had an electrician give me a new 200 amp drop and a new breaker panel.

My wife and I are about to upgrade our wiring and get the last of the knob and tube out of our house so I started googling and looking at numbers.

The panel is rated for 125 amps, yet the electrician put in 155 amps worth of breakers. It was permitted and I was there when it passed inspection so I'm guessing this is ok.

1. I have a feeling that the panel is rated based on total load capacity... but I was wondering if there's a formula for how much you are able to exceed the panel's rating with breakers?

2. Because the panel is located in my kitchen, I was hoping to not have to upgrade the panel for purely aesthetic reasons. ( I will if I have to) Can I run a line to another 100 amp rated sub panel from my current 125 amp panel to serve 2nd floor? Or does that require a 200 amp main?

Thanks for the advice!

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Old 08-28-2011, 02:05 PM   #2
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125 amp rated breaker panel yet I have 155 amps worth of breakers???


Adding up the breaker ratings is an incorrect way of sizing the service or seeing if it is the correct size. It does not take into affect that the 15 amp bedroom circuit only has an alarm clock that draws 50 watts on it nor does it account for any diversity and things like AC and heat that are not used at the same times. It is common for a 200 amp panel to have 4-600 amps of breakers in it.

The correct way is called a demand load calculation and is based on square footage and actual nameplate data from the installed equipment.

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Old 08-28-2011, 02:18 PM   #3
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125 amp rated breaker panel yet I have 155 amps worth of breakers???


Thank you Jim!

That is extremely helpful.

Would you be able to answer the second question I had, also:

Because the panel is located in my kitchen, I was hoping to not have to upgrade the panel for purely aesthetic reasons. ( I will if I have to) Can I run a line to another 100 amp rated sub panel from my current 125 amp panel to serve 2nd floor? Or does that require a 200 amp main?


Thanks again!
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Old 08-28-2011, 02:25 PM   #4
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125 amp rated breaker panel yet I have 155 amps worth of breakers???


That would depend on the existing load on the panel and how much reserve capacity is left over along with the proposed loads. You need to do the calculation to see.
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