GFP vs 6 Main

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Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
Customer is planning on adding some refrigeration units. The changes will require an upgrade from the existing 800 MDP with 6 mains, to a 1200. 480/277.

The best layout for me is to go back in with a 6 main, 1200 amp. The gear will fit and connection to the existing equipment will be easier.

I touched on having a main breaker similar to a 1600 amp service at another location. He wants to know if one is safer than the other. 6 Main vs GFP.
Other than limiting a ground fault current to a value and time is it safer? I believe they are starting to think OSHA and Arc Flash.

Existing MDP and new are and would be fused.
 

ron

Senior Member
If the 1200A main will be in a separate enclosure, it will result in much lower calculated arc flash incident energy for the (6) distribution switches, since it is more likely to require attention. This only works if they will calculate IE as opposed to using the 70E tables (if they apply anyway).
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
If you want to detect and quickly clear the most likely fault in your system, you should have GF protection.
With proper settings the main GF can almost always be set to coordinate with ranch devices as small as 30A.

My preference is to add a second level of GF, like in hospitals, rather than eliminate it at the main.
 
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