Electrical Eye-Wash/Shower / Panel Sizing

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PSU Electrical

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Project I am involved with is installing (5) combination Eye-Wash/Shower stations. They are electric, on-demand for tempered water and cut sheet states they are 126kW and 152A at 480V, 3-phase. They are all located in an area about 250' by 200', not all in straight line of each other (you'll understand why I present this area). Client requested putting these (5) units on a separate panel so we don't use up pole space off the main gear which I think is a good idea. Question is - what size panel do I need to go with and is there an exception is the code I can reference to avoid sizing the panel to the full demand if all (5) were running? The likelihood of having to use (5) of these at the same time is probably impossible, but I felt like if I sized the panel for worst case running (2) of these units, a 400Amp panel would suffice. Can I reference 220.60 as an exception to not sizing the panel for all (5) units running? Thougths?
Thanks.
 
My thought (not as an expert) is that you would need to substantiate that these would be non-coincident loads.

Your gut feeling is that the showers will rarely be used, and that 2 at once is a worst case. Sounds pretty reasonable to me. (I did my undergrad in a chem lab. The only time the showers were used was for testing.) But have you actually looked at any data supporting your gut feeling? Perhaps in lab accidents you either have no people involved or a bunch, and it is likely that the showers will never be used...but if they are needed then _all_ of them will be needed.

I would suggest having the designer who specified the showers and their location review the requirements to see if there is a standard for simultaneous operation of safety showers. All of the easy references that I could find specify things such as '20 gallons per minute of tepid water', but don't provide for diversity factors in the water supply. There probably are diversity factors buried somewhere in the code for the showers, and the designer should be able to pull that information out.

IMHO The diversity factor for the water flow to the showers provides a reasonable basis for the electrical power requirements.

-Jon
 
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