olsondavidj
Member
- Location
- Raleigh-Durham, NC
So I recently started a new job in a new city, and while they're waiting for some big orders to hit they've asked me to overhaul the control panel for a mobile test skid out in the shop (they're adding some motors and a touchscreen).
Anyhow, while I was working on it, I noticed the plug hanging from the overhead bus was a 3p4w twist-lock rated for 125/250VAC. The problem here is the overhead bus is a 480Y/277V supply. I promptly locked out the CB feeding the bus.
So the setup is it's a 600A overhead bus protected by an 800A breaker. There are 4 drops: 2 of them are unused, 1 is cord connected to a machine, and the one I'm working on has a plug dangling from the end of an 8/4 cable and is protected by a 30A fused disconnect switch up top.
So, I'm trying to find a replacement for this and I'm having some issues. The new test skid panel will be 26 FLA with 15HP worth of motor load (10 + 2 + 3). Unfortunately, the motor loads can all run simultaneously. What I've found is that 30A plugs only have 5hp ratings attached to them. Hubbell has a 50A plug, but it isn't HP rated. The only options I've found so far are a 100A pin-and-sleeve plug and connector, totaling $700, or I can get a reverse service interlocking plug/receptacle set for $2500+.
Either of these will be tough sell for our shop manager, since they're a far cry from the $50 that our machinist bought the old [wrong] plug for at Lowe's.
So I guess my question is: Do I need a HP rated plug/receptacle for this application? Or will an amp rated plug suffice?
In case it matters, the skid panel in question has a UL98 fused disconnect switch.
As a background note, I'm used to dealing with UL508A, and while that has a little bit to say about plugs/cords used for loads or interconnects, it doesn't really say anything about the plugs used to feed the panel. NFPA79 doesn't say anything either that I could find.
So the only thing I can find that would save me so far is that I could mark the receptacle with, "For disconnecting use only, not for current rupturing" per UL508A 59.4. But in this case, does the plug need to be mounted through the enclosure wall, or can it be cord connected (on say a 3ft cord)? I can't really find anything in UL508A that deals with this situation.
As an aside, am I even allowed to put a 100A plug on a 30A circuit? I don't know any specific rule against it, but I know it's generally bad form to do that since someone might actually plug a 100A load in to it.
Anyhow, while I was working on it, I noticed the plug hanging from the overhead bus was a 3p4w twist-lock rated for 125/250VAC. The problem here is the overhead bus is a 480Y/277V supply. I promptly locked out the CB feeding the bus.
So the setup is it's a 600A overhead bus protected by an 800A breaker. There are 4 drops: 2 of them are unused, 1 is cord connected to a machine, and the one I'm working on has a plug dangling from the end of an 8/4 cable and is protected by a 30A fused disconnect switch up top.
So, I'm trying to find a replacement for this and I'm having some issues. The new test skid panel will be 26 FLA with 15HP worth of motor load (10 + 2 + 3). Unfortunately, the motor loads can all run simultaneously. What I've found is that 30A plugs only have 5hp ratings attached to them. Hubbell has a 50A plug, but it isn't HP rated. The only options I've found so far are a 100A pin-and-sleeve plug and connector, totaling $700, or I can get a reverse service interlocking plug/receptacle set for $2500+.
Either of these will be tough sell for our shop manager, since they're a far cry from the $50 that our machinist bought the old [wrong] plug for at Lowe's.
So I guess my question is: Do I need a HP rated plug/receptacle for this application? Or will an amp rated plug suffice?
In case it matters, the skid panel in question has a UL98 fused disconnect switch.
As a background note, I'm used to dealing with UL508A, and while that has a little bit to say about plugs/cords used for loads or interconnects, it doesn't really say anything about the plugs used to feed the panel. NFPA79 doesn't say anything either that I could find.
So the only thing I can find that would save me so far is that I could mark the receptacle with, "For disconnecting use only, not for current rupturing" per UL508A 59.4. But in this case, does the plug need to be mounted through the enclosure wall, or can it be cord connected (on say a 3ft cord)? I can't really find anything in UL508A that deals with this situation.
As an aside, am I even allowed to put a 100A plug on a 30A circuit? I don't know any specific rule against it, but I know it's generally bad form to do that since someone might actually plug a 100A load in to it.