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A #3 copper conductor with an insulation factor of 90 degrees C is rated at 115 amps. Even though the panel is rated at a higher amperage it is the main breaker that governs the wire size.

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Q: What wire size do you need for a 125 amp panel with a 100 amp main breaker?
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Do you need a main disconnect on the feeder wires running to a detached garage running from the box in the house?

Yes you do. The detached garage will either be fed with a single circuit or a sub panel. The wire feeding the garage will need to be protected and that is the purpose of the breaker (disconnect). The breaker size will be determined by the size of the wire that is used on this circuit.


Can you downgrade from a 125amp main breaker to 100 amp breaker using the same box?

You can reduce the breaker size because that limits the current that can reach the main panel. There is no safety issue other than the significant danger in an unskilled person changing out a main breaker.


What size breaker do you use for a 100 amp sub panel?

A 100-A sub-panel would be fed from a 100-A breaker.


Can you put a 60amp breaker and a 50amp breaker on a 60amp subpanel just as long as they are not being used at the same time?

You can. Using these size breakers in a 60 amp sub panel might be pushing the limit for breaking the sub panels feeder breaker. The breaker feeding the sub panel will have to be no bigger than 60 amps because of the main bus bar capacity of the sub panel. It would be better to install a 100 amp sub panel and then there would be a bit of a buffer and you will have the ability to add additional small load circuits.


How can you tell what your home amp service is?

Look on the handle end of the main breaker. There should be a number there. That is the amperage of the main breaker. That is the size of your house service.

Related questions

What is the smallest size circuit breaker found in the normal home?

The biggest circuit breaker in any home is the main breaker located in your main breaker panel that is installed where your electrical service cable comes into your home.


What is the minimum size breaker panel for a home's main service?

50 amps


What is the minimum size breaker panel required for a homes main service?

50 amps


Do you need a main disconnect on the feeder wires running to a detached garage running from the box in the house?

Yes you do. The detached garage will either be fed with a single circuit or a sub panel. The wire feeding the garage will need to be protected and that is the purpose of the breaker (disconnect). The breaker size will be determined by the size of the wire that is used on this circuit.


How do you read breaker box amps?

The main breaker will have marking indicating size of electrical service, or if it is a fuse system....the fuses will have current ratings. If it is a subpanel, it might not have a main breaker. In this case you would have to look in the panel that the feed is coming from and find the size of the breaker that is feeding it. In either case you must look for the manufacturer's label that will have the maximum current the panel can handle, make sure the breaker feeding the panel doesn't exceed this rating.


What is the minimum size breaker panel for a home?

In North America the smallest size breaker found in a home distribution panel is rated at 15 amps


Is the main circuit breaker is a sum of the sub circuit breaker?

Typically yes because that is what makes sense. However, the subpanel could have the same size breaker as long as the panel were rated for that amperage and the wire sizes were appropriate.


Can you downgrade from a 125amp main breaker to 100 amp breaker using the same box?

You can reduce the breaker size because that limits the current that can reach the main panel. There is no safety issue other than the significant danger in an unskilled person changing out a main breaker.


What would happen if a 200 amp breaker is used in a 100 amp sub panel?

There are two things to think about here. First of all a 200 amp breaker will not physically fit into a 100 amp panel. This is so designed because the panel buss is not designed to conduct 200 amps before the current is cut off. A 100 amp rating on the panel is the maximum amount of current that the manufacturer states, that can be handled safely. Second if the 200 amp breaker is in the main panel then everything downstream from that breaker has to be rated for 200 amp conductivity. The wire size will have to be 3/0 from the breaker to the first over current device in the sub panel which will be the sub panel's main breaker. The sub panel can not be a load center but will have to be a combination panel. I doubt that the 100 amp sub panel's main breaker lugs would be large enough to connect the 3/0 cable.


What size breaker do you use for a 100 amp sub panel?

A 100-A sub-panel would be fed from a 100-A breaker.


What size wire and breaker do you need to run a 9000max watt generator?

If it is a portable generator the breaker should be self contained within the generators panel. If the generator is a stationary standby unit a voltage has to be stated to calculate the conductor size and hence the breaker size to protect the conductor. Amps = Watts/Volts.


If an electrician have a circuit that pulls a load of 10 amps what size breaker must that circuit be protected by?

If you are talking about a breaker in a house panel then a 15 amp breaker would be used. It is the smallest amperage breaker that you will find in a house panel.