Jeff_M_PA
Cast Iron
- Joined
- Oct 31, 2008
- Location
- San Diego, CA
In a moment of stupidity, I bought on eBay what I thought was a used 500A molded case circuit breaker for 480v 3-phase service (should have known it was too good of a deal). When it arrived today, my maintenance guy said, "hey dummy, why'd you buy a DC breaker?"
It's a (really nice) Square D Cat #MHL3650032DC Series 2. So, I did a little Googling, and I found out, in caveman terms, that DC breakers have to be much more "King Kong" to break x amount of DC current than an equivalent AC breaker. Lots of references online say "no, you can't use that AC breaker on your DC system", but no references I found address the opposite situation of using a DC breaker on AC.
Yes, I know the right answer (given that this is obviously a safety issue) is probably to buy the correct breaker, and just re-sell this one, and that's probably what we'll do, because I would imagine no inspector is going to pass it anyway. But, I'm curious; it looks like it should work.
If it matters, this will be a 400A 480V 3-ph main service, and was intended to replace our last remaining fused disconnect. We have two other 400A services and one 800A now.
Jeff
It's a (really nice) Square D Cat #MHL3650032DC Series 2. So, I did a little Googling, and I found out, in caveman terms, that DC breakers have to be much more "King Kong" to break x amount of DC current than an equivalent AC breaker. Lots of references online say "no, you can't use that AC breaker on your DC system", but no references I found address the opposite situation of using a DC breaker on AC.
Yes, I know the right answer (given that this is obviously a safety issue) is probably to buy the correct breaker, and just re-sell this one, and that's probably what we'll do, because I would imagine no inspector is going to pass it anyway. But, I'm curious; it looks like it should work.
If it matters, this will be a 400A 480V 3-ph main service, and was intended to replace our last remaining fused disconnect. We have two other 400A services and one 800A now.
Jeff