Fault Current at Elevator Controller

[charlie b]

Local authorities have recently been pushing design firms to demonstrate that the calculated short circuit current available (SCCA) at the location of an elevator controller is below the controller’s short circuit current rating (SCCR). I haven’t seen them cite 110.10 as the basis for this push, but I don’t think I could win an argument if they did. The elevator manufacturers all seem to offer SCCR values no higher than 10KA. We have a current project that has a calculated SCCA of 82KA. The three solutions that come immediately to mind are all energy wasting, money hogging, and (gasp!) disgracefully inelegant.

1. Have you encountered this issue?
2. What solutions have you used (or at least tried)?

 

[dkidd]

1. Yes
2. Transformer

 

[charlie b]

Thanks. "Transformer" was one of the three to which I alluded. The other two are "inductive choke" and "long feeder." Of course, the best solution is for the elevator manufacturers to select the appropriate components for their controllers, and get them listed for higher SCCR values. But there seems to be nothing to motivate them into making that move.

 

[dkidd]

You can keep rejecting the submittal, but in the end the supplier can outwait you, and the Owner and Architect will tell you that "no one else has ever required it", and "the supplier knows what he is doing".

And a long feeder would mysteriously get shorter one day, as copper prices increase.

 

[chris kennedy]

Is 82KA a typo?
How could that be?

 

[charlie b]

I wish it were a typo, Chris. This is for a new high rise building being designed for downtown Seattle. There will be three service transformers (1,500 KVA, 480/277V) in a network configuration within the utility's vault. The utility is telling us that their SCCA value is 138KA at the collector bus. The elevator controller that is facing an 82KA fault is in the basement. Other elevators have their equipment higher up in the building, so their SCCA values are not that high. But they are all over 10KA.

 

[don_resqcapt19]

Charlie,
You just have to take the feeder conductors to the elevator penthouse and back down to the equipment room

 

[don_resqcapt19]

I am kind of surprised to see the 10k value...I though a lot was just sent out at the default value of 5k.

This is a problem with a lot of equipment now with many code rules calling attention to the SCCR requirements. A lot of large HVAC units have a 5k rating and have available fault currents well above that.

At some point the designers and ECs need to pressure the equipment manufacturers to make panels with a suitable rating.

 

[victor.cherkashi]

Is it possible to use curent limiting device? Fuse or circuit breaker?

Sent from my Nexus 5 using Tapatalk

 

[dkidd]

Only if the equipment manufacturer lists it that way.

There is a good article at http://ecmweb.com/design/sccr-liability-trap