SCCR - Packaged Air Compressor

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Retired Electrical Engineer - Power Systems
But since the arc only holds the stage for fractions of a millisecond why is it considered a show stopper????
Partly because every major fuse manufacturer says it is a problem. For some 4 decades now, they have warned not to do, what you suggest might be okay.
 
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nhee2

Senior Member
Location
NH
The manufacturer could probably make that affirmation only if they had actually tested, not just done simple calculations. (Because of the dynamic characteristics of CL fuses.)
The panel is an assembly of components that presumably all have SCCR values based on mfr testing. Presumably some of them (like the distribution block) have one rating if protected by a specific OCPD, and another if not. I am only talking about trying to get the compressor vendor to evaluate whether CL fuses would allow an alternate SCCR based on the component ratings in their assembly. No testing or similar is intended.

In my original post I had suggested replacing a couple components ourselves to achieve a new rating with CL fuses, but petersonra's first response provided some guidance that this would not really achieve what I wanted to achieve.
 

charlie b

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Staff member
Location
Seattle, WA
Occupation
Electrical Engineer
How about putting a line reactor ahead of your equipment?
We are designing several high rise buildings in downtown Seattle, and that is the solution we are planning to use. It helps that SKM has a way to include the line reactor in the model, so I can select the size of the line reactor to get the SCCA down to where I need it.

 

nhee2

Senior Member
Location
NH
We are designing several high rise buildings in downtown Seattle, and that is the solution we are planning to use. It helps that SKM has a way to include the line reactor in the model, so I can select the size of the line reactor to get the SCCA down to where I need it.

Charlie b is that for feeders to distribution panels? Feeders/branch circuits to control panels/motor loads? Al of the above? Do you have any particular vendors you have specified?
 

charlie b

Moderator
Staff member
Location
Seattle, WA
Occupation
Electrical Engineer
Charlie b is that for feeders to distribution panels? Feeders/branch circuits to control panels/motor loads? Al of the above? Do you have any particular vendors you have specified?
At the least, it will be feeders to branch panels that serve multiple elevators. It may also be branch circuits for HVAC equipment. We haven't gotten to the stage where we would be looking at vendors of the line reactors yet.

 

kwired

Electron manager
Location
NE Nebraska
Possibly. I assume (but have not looked at pricing to confirm) that installing longer conductors will be more cost effective, although not very elegant.
The 75 hp compressor I mentioned earlier in the thread the CL fuses the vendor required were about $160 each vs about $55 for RK-5 fuses. That difference alone probably puts a good dent in the cost of a line reactor.
 
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