ss electric1
Member
- Location
- nc
house panel. how do you add up number of circuit breaker (amps) 100% cont. duty. 80% main breaker rating. I have noticed when you add up amps it exceeds panel rating. thanks
panel load
- Thread starter ss electric1
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Load calculation, power company demand (good only for a service panel), or 30-day monitoring per Article 220 are the only compliant methods.
Summed up breaker ratings will typically be greater than the panel's rating even when everything is up to snuff code-wise.
BTW, welcome!
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
You do not calculate service or feeder load based on adding the circuit breaker amps together. Not all these breakers are necessarily loaded to 100%, not all of them are necessarily loaded simultaneously. Use art 220 calculations to determine what minimum size is necessarily to feed the loads you have. 220 does apply demand factors to certain items.
Consider the fact that a heating system and a cooling system are not to be intended to run at same time, so therfore you can disregard the smaller of the two to some extent to get a real loading situation. Appliances with heating elements typically do not draw full amps continuously, they cycle on and off as heat is needed. All the 220 calculations and demand factors take this into consideration, and just to be on the safe side, it often (but not always) still results in larger supply than what one may be realistically be able to get by with.
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