Location Wisconsin. Pilot Super Grip said:. Click to expand It is mentioned in Marking and Application Guide Moulded Case Circuit Breakers : Percent Continuous Rated - Unless otherwise marked for continuous use at percent of its current rating, a circuit breaker is intended for use at no more than 80 percent of its rated current where in normal operation the load will continue for three hours or more. Location Massachusetts.
Location Litchfield, CT. Why any number? Like why is it four or more conductors requires derating? Why is it not bundling at 23" but it is bundling at 25"?
The standard rating is subject to the NEC sizing rules we've just discussed. SteveR Member. Isn't a load considered continuous if it will carry its maximum current for 3hrs or more? Basically continuous loads are defined as any load where the maximum current is expected for 3 or more hours.
Mainly, but not exclusively Lighting. See the definitions Article This is my first time too but from all the examples I've seen Lighting would be the continuous.
That gives you your min size for the conductor. Apply and derating factor like more than 3 conductors. Overcurrent protection varies. Again generally the calculated number you got above, if it doesn't match a standard size, the next higher may be used.
For Motors depending on the device ie non-time delay fuse they call for, the percentage varies see Table For Motor Overloads use motor nameplate or given ampacity and Service factor. See Section Last edited by a moderator: Oct 25, That's perfect and I'm satisfied. Thanks for the reply!!! Post reply. Similar threads A. PPI Exam 1 Question Where a branch circuit supplies continuous loads, the minimum branch-circuit conductor size, before the application of any adjustment or correction factors, shall have an allowable ampacity not less than percent of the continuous load [ In other than dwellings, lighting loads are usually considered continuous.
For example, a branch circuit will supply power to high-intensity discharge HID luminaires in a warehouse. These luminaires will be energized for at least 10 hours per day. The luminaires will have a current draw of Because the load will continue for three hours or more, this branch circuit is considered a continuous load.
Therefore, multiply the load by percent The conductors must have an ampacity of at least 17A see Figure 1. If a branch circuit supplies both continuous and noncontinuous loads, the minimum branch-circuit conductor size, before the application of any adjustment or correction factors, shall have an allowable ampacity not less than the noncontinuous load plus percent of the continuous load [ Continuous loads are also a factor when sizing feeder conductors.
The minimum feeder-circuit conductor size, before the application of any adjustment or correction factors, shall have an allowable ampacity not less than the noncontinuous load plus percent of the continuous load [ After performing a load calculation in accordance with Article , divide the loads into two categories: continuous and noncontinuous. Multiply the continuous loads by percent, and add to that number the noncontinuous loads. For example, Article was used to calculate the loads for a feeder in a commercial building.
While the calculation results for the continuous loads were 92A, the results for the noncontinuous loads were 74A.
Start by multiplying the continuous loads by percent. The minimum ampacity for these feeder conductors is A see Figure 2. After continuous loads and noncontinuous loads have been added back together, the panelboard and conductors can be selected.
The feeder in Figure 2 must have a rating of at least A. Standard ampere ratings for fuses and inverse-time circuit breakers can be found in Since the result of the calculation in the last example was A, the minimum size breaker that can be installed for this feeder is A.
In accordance with Table
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