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According to this logic, one could chain an infinite number or sub-panels off of a single one hundred amp feed. The second law of thermodynamics prevents this. An hundred amp service is not capable of powering another hundred amp service unless you are trying to move your panel and all of the circuits it feeds as well, without adding another hundred amp load. NEC (National Electrcial Code NFPA Book 72) states that certain loads can be derated but not to this extent.

As far as the voltage drop is concerned, you need only worry about this with runs of about two hundred and twenty five feet or more for a 200 Amp Service running 2/0 2/0 4/0 URD direct burial aluminum.

What you need is a new 200 Amp service to feed your original 100A panel and another hundred amps to feed your new load.

for USA, Canada and countries running a 60 Hertz supply service.Yes you can as long as the feeder to the other 100 amp panel is equal to the ampacity of the breaker. In this case you would need to use a #3 wire rated at 90 degrees C if the distance to the other panel is under 50 feet. If the distance is longer that this a voltage drop calculation would have to be added to increase the wire size.


My experience would lead me to believe that you could not install a breaker that was greater to or equal to the rating of the main breaker. To add a sub-panel, you will need to install a breaker that is half or lower than the main breaker.

In your case, you have a 100A service; you will need to install a 50A or smaller breaker to service the sub panel.

Consult an electrician if in doubt.

If you have any doubts about an answer that you get, check the answerer's bio by clicking on their name to check their qualifications.

Before you do any work yourself,

on electrical circuits, equipment or appliances,

always use a test meter to ensure the circuit is, in fact, de-energized




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โˆ™ 2015-07-15 18:50:11
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Q: If the service panel you have 100A service can you install a 100A circuit breaker in the original panel to feed another 100A add-on panel?
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