Jeff Coggins
Member
Using a 225 Amp panel with a 225 amp 80 % rated main breaker, can a 200 amp non fused disconnect be used and still be within code. Since the max on the breaker is 180 Amps."
NON FUSED DISCONNECTS
- Thread starter Jeff Coggins
- Start date
- Status
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: NON FUSED DISCONNECTS
The disconnect has to be "rated for" (i.e., capable of withstanding) the highest current that will pass through it. It can be rated higher, but not lower.
The 225 amp breaker might be limited by some code sections to serving a load no higher than 180 amps. But it will not trip if the load were to reach 220 amps. That load could damage the disconnect. So you need to look at the connected load, not just the rating of the overcurrent device. If the load is, in fact, lower that 180 amps, then yes, you can use a 200 amp disconnect.
The disconnect has to be "rated for" (i.e., capable of withstanding) the highest current that will pass through it. It can be rated higher, but not lower.
The 225 amp breaker might be limited by some code sections to serving a load no higher than 180 amps. But it will not trip if the load were to reach 220 amps. That load could damage the disconnect. So you need to look at the connected load, not just the rating of the overcurrent device. If the load is, in fact, lower that 180 amps, then yes, you can use a 200 amp disconnect.
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
Re: NON FUSED DISCONNECTS
My guess would be, either the parts house fell through, or we're looking at the spare parts shelf.
Not around here.
My guess would be, either the parts house fell through, or we're looking at the spare parts shelf.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: NON FUSED DISCONNECTS
In an exchange of private messages, I have learned that I had interpreted the question incorrectly. I am told that from some (unnamed and undescribed) upstream panel, conductors lead first to the disconnect, and then to this 225 amp panel that has a 225 amp main breaker. I am still not certain why the disconnect exists.
So the question becomes this: Can you have a 200 amp rated disconnect in series with that panel? The question is being asked because of the expectation that the load will not exceed 80% of that 225 amp breaker (i.e., 180 amps).
In view of my new understanding of the question, I will have to change my answer. No this is not acceptable. The breaker is permitted to carry 100% of it rated current, so long as it is not a "continuous load." But you can pass 224 amps through that 200 amp disconnect for 179 minutes, without violating the rule about breaker sizing. This would, however, violate the rule about operating a component (i.e., the disconnect) beyond its rating.
In an exchange of private messages, I have learned that I had interpreted the question incorrectly. I am told that from some (unnamed and undescribed) upstream panel, conductors lead first to the disconnect, and then to this 225 amp panel that has a 225 amp main breaker. I am still not certain why the disconnect exists.
So the question becomes this: Can you have a 200 amp rated disconnect in series with that panel? The question is being asked because of the expectation that the load will not exceed 80% of that 225 amp breaker (i.e., 180 amps).
In view of my new understanding of the question, I will have to change my answer. No this is not acceptable. The breaker is permitted to carry 100% of it rated current, so long as it is not a "continuous load." But you can pass 224 amps through that 200 amp disconnect for 179 minutes, without violating the rule about breaker sizing. This would, however, violate the rule about operating a component (i.e., the disconnect) beyond its rating.
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