Temporary power for outside use

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dneveaux

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I am looking to have some distribution panles built for temporary electric use outside. The Panels are a Nema 3R and have flush mounted Cam-lok connections as an input. These are rated at 405 amps. The output will be either L21-30 or L21-20 twist-locks put on a 30 or 20 amp 3-pole breaker. There will be 6 of the twist lock outputs. My questions is a 400 amp disconnect ok to use as the means of disconnect. I will be coming of a 225 kw generator (800 amp main) with a 10-15ft set of 4/0 tails. Then feeding the panel with 4/0 Type W. My biggest question is does the distro panel need a main disconnect? The distro panel will have the 30 amp breakers protecting the number 10 and the 400 amp protecting the flush mounts. Can I go from the flush mounts to the line side of a 30 amp breakerwith # 10? I hope this makes sense. Thanks for your time. If you could let me know where in the code you are basing an answers on.

Dave
 
Your 4/0s running from the genset are tap conductors and need protection per 240.21(B). You need a main at the panel that has an OCPD rated 360 amps or less to protect the 4/0s. Note this assumes that the termination points for the 4/0 are listed for use with 75?C conductors.
 
I will be using a 400 amp switch at the Genset. Then feeding each panel with 4/0. Do I need anything else to protect the distro panel?
 
In that case you are good to go, assuming that the panel is rated at 400 amps and the acutal load is 360 amps or less.
 
This is another one of those occasions where you need to do the right installation, whilst ensuring that it happens to be NEC compliant.

Yes, the distro should have a disconnect, 'cos someone may want to turn stuff off in a hurry.

Yes, you need to protect the camloc cables at the genset end, as your genset can deliver far more current than they are rated for.
 
Seems like it would be easier to buy a preassembled (and tested/listed) unit. I'm a fan of Lex Products & Kolher, but there are others. (I haven't built a box like that in ages, I either buy/rent/borrow that sort of stuff.) You're kind of look at a Kohler DB200A-XO16369.

Oh, and it you're starting with a >400a3p feed and breaking down into L21's, you might want consider subpanals....
 
The Lex products, or similar, are what I am talking about. I believe Lex builds Kohler panels. My question is why is a panel, The DB200a-xo16369, rated at 200 amps? If the Cams are rated at 400 amps and the twist locks are protected at 30 or 20 amps can I use the 400 amp switch at the Genset as a legal overcurrent means? I spoke with Lex and what I am looking for is something out of the code that will allow me to use these panels without a 200 amp disconnect or main. (other than the 400 at the genset) To summarize: why can or can't this panel be protected by a 400 amp disconnect? And where is that backed up in the code? Specifically please. I am looking to purchase several of these and I want it done right but a 200 amp main on each panel is a pretty significant expense. Thanks.
 
dneveaux said:
The Lex products, or similar, are what I am talking about. I believe Lex builds Kohler panels.
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Lex does build for Kohler, but Lex has changed some of the designs, and I prefer some of the older ones. BTW, there are a fair number of companies building temporary power distro. Google for 'temporary power systems'

dneveaux said:
My question is why is a panel, The DB200a-xo16369, rated at 200 amps? If the Cams are rated at 400 amps and the twist locks are protected at 30 or 20 amps can I use the 400 amp switch at the Genset as a legal overcurrent means?
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Two different questions- The panel is rated at 200a because that's were Lex rated it. I'll assume that it's based on the internal wiring from the input to the breaker bus. Second answer- No, the panel is rated at 200a so it should be protected at 200a.

dneveaux said:
To summarize: why can or can't this panel be protected by a 400 amp disconnect? And where is that backed up in the code?
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...because it's rated at 200a. Look in the sections on panels for the exact citation. (Do you mean 'disconnect' or breaker/OverCurrent Protection? A disconnect might not have OCP.)

dneveaux said:
I am looking to purchase several of these and I want it done right but a 200 amp main on each panel is a pretty significant expense.
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You need the 200a OCP somewhere. The usual practice, at least the practice that I'm familiar with, is to take the generator output into a large distro panel, then from there run properly protected feeders to smaller branch-circuit panels. You can combine these, but as you've found, it costs more. IMHO it also limits flexibility. BTW, I've been able to purchase rental stock for much less than new/retail prices.

Remember that the purpose of a breaker is to protect everything downstream of it. A 400a breaker can't protect a 200a-rated device.
 
The information says it is a 200 amp panel. You would have to check the UL Listing information, but I am not sure that it is really a listed product and the online information only talks about it being listed as a "3R" enclosure. It is my opinion that based on the manufacturer's information this panel is to be used on circuit rated 200 amps or less. I would like to say that it is a panelboard and 408.36 applies, but I am not sure that it is a panelboard.
 
Thanks again for taking the time to help me out. Still don't get why Lex, or whoever, is rating these at 200 amps. What is their basis for it. In the reply it was assumed because of internal wiring to the breaker bus. These panels don't have a main bus. They go from the 400 amp cam input, (an internal lug) to the line side of the 30 amp breaker with a #10 wire. I spoke with Lex and was told I did not need a 200 amp disconnect or main on the panel but they could not give me the reason why, as per code. That is what I need to satisfy any inspectors. Lex is telling me on thing and they build it and others are saying something else.
 
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