Elevator Control Switch Fuses

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PE (always learning)

PE (always learning)

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Saint Louis
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Professional Engineer
I'm working on a project where we are using Kone elevators and the Kone submittals call for Class RK1 fuses, but the upstream elevator control switches that have already been ordered can only accommodate Class J fuses.

Is there a reason why this elevator can only be protected by class RK1 fuses?

I created some time current curves and tested the motor inrush against the fuse and saw no issue with class J fuses.

See attached for elevator submittal.
 

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Kind of pointless that they stipulate RK1 fuses, but not their equipment's SCCR. It could well be that your particular installation doesn't exceed the SCCR and current-limiting fuses aren't required.
 
It was probably tested for short circuit current using RK1 fuses. The labeling is based on RK1, so without re-testing, I doubt they are going to agree you can use Class J. Different fuse classes have somewhat different current-limiting characteristics. I would inquire with Kone, but not get my hopes up.

I have seen installations of package systems where a fused disconnect was installed directly adjacent to a MCCB because that it was their UL label was based on.
 
JoeStillman said:
Kind of pointless that they stipulate RK1 fuses, but not their equipment's SCCR. It could well be that your particular installation doesn't exceed the SCCR and current-limiting fuses aren't required.
Click to expand...
Yea this is an odd submittal as they don't even list the short circuit current rating based on those fuses. Seems kind of pointless
 
David Castor said:
It was probably tested for short circuit current using RK1 fuses. The labeling is based on RK1, so without re-testing, I doubt they are going to agree you can use Class J. Different fuse classes have somewhat different current-limiting characteristics. I would inquire with Kone, but not get my hopes up.

I have seen installations of package systems where a fused disconnect was installed directly adjacent to a MCCB because that it was their UL label was based on.
Click to expand...
This stuff drives me crazy, why should I be limited to only using one specific fuse type in this scenario. Class J fuses are used in quite a few applications and it annoys me when manufacturers do crap like this...

The available fault currents at my elevators are all well below 10,000 amps so I don't need to achieve that high of a rating, but I guess if Class J fuses aren't tested with this equipment then that equals no rating?
 
I used to deal with this issue dealing with HVAC air handlers and other equipment. We just installed exactly what the manufacturer called for as a local disconnect regardless of the situation. It just wasn't worth the time to fight it. Your local AHJ could always approve the Class J fuses, but again, it was rarely worth our time to argue it out. Elevator equipment seems to be in its own world most of the time.
 
God forbid if something should happen with the elevator but if it ever did a whole bunch of folks will be looking for a scapegoat.
I would not want tyo put myself in a position of altering any thing they specified.
 
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