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Why does the main circuit breaker trip but not the smaller branch circuit breakers?
Wiki User
∙ 8y ago
If the main breaker has ground fault detection, and the fault is a ground fault, then only the main may trip.
Also if the fault is a direct short, the fault current may be several thousand amps, much greater than the trip point of both breakers. Breakers have an I^2T curve (current squared-time), which is an indication of how fast the breaker will trip at a given overload. When both breakers are overloaded, the breaker with the faster I^2T rating at that current level will trip first. This would be an indication that the breakers are improperly specified or adjusted.
Wiki User
∙ 13y ago
Wiki User
∙ 8y agoWhat is happening is that the total branch circuits are drawing a total greater than the main breaker rating. For an example when you look at a distribution panel you will see at a minimum of 20 breakers on a 100 amp rated panel. Maybe more or maybe less it doesn't matter. Total the branch circuit breakers and add up their total amperage. On a 20 amp panel full of 15 amp breakers there could be a possibility of 300 amps. Because the chances of all breakers being on at once is very slim this is why that many breakers are allowed in a distribution panel. Usually a fully loaded 100 amp panel at any given time will be drawing in and about 50 to 60 amps. This gives you about 40 amps spare before the main breaker will trip. In your case you have loaded the panel to the maximum allowed amperage and the main breaker trips to protect the distribution panel from overloading. Turn off some of the loads and see if the main breaker trips. If it doesn't then this is why the main breaker is tripping. If you need a high amount of current draw from this service then it is time to upgrade to a larger service.
Wiki User
∙ 8y ago.
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What type of circuit breaker is required for a 240 v branch circuit?
the circuit breaker used will be miniature circuit breaker(MCB) maily used in homes.Answer for USA, Canada and countries running a 60 Hertz supply service.A two pole circuit breaker is used for a load of 240 volts. It is sized, according to the load amps of the device, to protect the wires that supply the load current.
What is the main function of an electric circuit?
The purpose of an electrical panel board or electrical distribution panel is to supply individual circuits from the main distribution board. As the board is supplied with one circuit of high capacity , it needs to be broken down into smaller branch circuits. Breakers accomplish this obligation by plugging into the panels main bus-bars. The load side of the breaker then goes to the specific load. The size of the breaker is dependant upon the size of the load of that circuit. The conductor that feeds the load is dependant upon the size of the breaker feeding that load.
Where is main breaker switch?
a circuit breaker trips on overload,if this breaker has tripped many times it may be worn out,if there is a overload happening the breaker is doing it s job keeping you safe.Main breaker needs to be replaced when your meter has been pulled(removed from metersocket)Have a electrician look at it and verify problem, you should not attempt to change out yourself it will be live.......
What is a arc fault breaker?
All circuit breakers are designed to extinguish the arc created when the circuit breaker interrupts an electrical fault current. High-voltage circuits breakers use various techniques such as stretching and cooling the arc, and replacing the arc's path with a dielectric to prevent it from restriking.
What formula do you use to tell if you'll overload a breaker?
Use the Watts = Amps x Volts formula. Most appliances will have the wattage on the nameplate. Nameplates that have the amperage on them will be the size of the breaker that should protect that device. There is an exception for motor loads, breaker size is 250% of full load amps. Divide the watts by the voltage and you will get the amperage of the device. This amperage will govern the size of the breaker to use. Breakers start at 15A, then 20A,30A,and 40A for most branch circuits in a house.
What circuit breaker is used in a load center?
Don't Understand your question, all of your circuit breakers start at the load center and then branch out to your recepticles(plugs) ETC.
Can you run an extra set of wires off a 20 amp breaker?
No, this is stated very clearly in the electrical code. Only one branch circuit is to be allowed connected to each individual circuit breaker no matter what the amperage is. If a new branch circuit is installed and there are no spare breakers then most distribution panels have the ability to let tandem breaker be installed in it. Tandem breakers have two terminals and two handles and have the ability to fit into a single slot in the distribution panel.
What is the maximum number of branch circuit breakers allowed in a 100 amp panel?
I just spoke with an inspector here in NJ today and according to him pending on what panel(squareD)in this case, it is 24 space but can be 48+. Stating that the breakers allow you to place two branch circuits on one breaker. Didn't make sense to me, being that while in school at my union it was 1 circuit for each breaker. Unless, some tandem breakers are used. Check the breaker and see what its rated for. Hope this helps.
Is a circuit breaker required on every branch circuit?
yes
What causes the main breaker to trip from a fault current from a twenty amp branch circuit?
If the fault was on the 20 amp branch circuit, the branch circuit breaker should have tripped, not the main breaker. Call a qualified electrician to check out your wiring.
How are Branch circuit protected?
Branch circuits are protected by the circuit breaker found in the electrical panel. Each circuit should have its one breaker. The breaker should be rated to protect the insulation of the wire, so you can determine the breaker size based on the circuit conductor size Example #14-2 should be protected by a 15 amp breaker
How can you tell if a home fuse is open?
Usually there will be lights or equipment in the house that will not operate. If all of the branch circuit breakers or fuses have not tripped or blown the only conclusion left is that the main breaker or fuse has tripped or blown.
What is the difference between a run and a circuit?
run in a electrical system means a wiring & conduit runs coming from Panel Board Circuit Breaker to its branch circuit loads in a circuit. while circuit is a designated number of branch breaker in a panel board where power load was individual connected.
What is a ark fault circuit breaker?
install breaker in panel and put the hot wire on the breaker and also there should be a place for the neutral on the breaker also both wires will be landed on the breaker in different spots and then take the white wire that is coiled on breaker and land it on the neutral bar
What is a branching circuit?
Each of the circuit breakers in the service panel controls electricity on a branch circuit. A branch circuit is typically a loop of wire that runs from the service panel, out to receptacles, light fixtures, appliances, etc. and back again.
What is the purpose of a branch circuit?
To supply power to all electrical devices in a house, apartment, condominium, etc. A branch circuit is connected to the circuit breaker panel which is usually found in a closet or a cupboard
Does the code permit the ampacity of switch legs to be less than the ampere rating of the branch circuit?
No, and here's why: the rating of the branch, determined by the overcurrent protection, is designed for the ampacity of the branch conductors so that they breaker trips before the conductors heat up enough to start a fire. If you put in smaller wires on the same branch, they will get MUCH hotter before the circuit breaker trips, if it ever does. For example, a 20A branch, protecting 12AWG wiring; add some 14 AWG rated for 15A. Something faults the switched leg at 18A; enough to burn out the wiring but not enough to trip the breaker. House burns down, insurance doesn't pay because of "faulty wiring" installed negligently by a person without proper training and credentials.
