Elevator Controller SCCR

[charlie b]

We are encountering a problem more and more these days, and all of the solutions we know about are bad ideas. The issue is the short circuit current rating of elevator controllers, and several local jurisdictions are making an issue out of it. Most often it is shown as 5,000 amps, and occasionally is shown as 10,000 amps. The available fault current is often above 20,000 amps, and the elevator manufacturers are not willing to get their equipment tested and listed for higher fault currents. The solutions I have seen used include 1:1 transformers, increasing the length of the feeders, and installing current-limiting fuses. That last item is not viable, if the elevator controller has circuit breakers that serve the motor loads. A coworker just suggested feeding the elevators from a 208 volt bus, and using a 208-480V step up transformer to insert some impedance into the circuit.

Anyone have any better ideas?

 

[don_resqcapt19]

This is happening with other equipment such as HVAC equipment. Not sure what the solution should be.

It is really a problem for the equipment manufacturer's to fix, but they don't seem to be willing to do that.

I would like to suggest that the required SCCR be in the equipment bid specs, and that the owners and engineers stand firm in rejecting bids from manufacturers who do not comply with the specs. I know that is not likely to happen, especially where there are no manufacturers offering a compliant product.

Maybe, if the equipment manufacturer has not not taken exception the the SCCR spec in his proposal, the costs of making the electrical system suitable to supply the non-compliant equipment should be deducted from the payment for that equipment.

That being said, the only other option that you haven't listed would be adding impedance to the supply circuit using a reactor.

 

[petersonra]

few suppliers are going to put themselves at a competitive disadvantage by quoting something that costs more than what the customer asked for.

having said that, in many cases it is not especially hard these days to do better than 5 or 10 kA without adding cost. It does require some redesign though and I can understand why a supplier would not want to spend the money to do it unless it was justified.

 

[Jraef]

What kind of elevator controllers are you looking at? Most of them are just standard starters and such, so the issue most likely is just that the OEMs are too lazy to check into it very deeply, preferring to kick the can down the road. Were they to check, they might find it's not that difficult to get a higher rating, but it will involve using common products, i.e. the breaker and starter from the same mfr so they are tested together by them.

The problem is, and I have experienced this first hand in the elevator biz, that this interferes with the OEM's purchasing dept. who wants to play every supplier against each other for each component as a stand-alone commodity, meaning they'll get 6 suppliers to kill each other on pricing for starters today, then circuit breakers tomorrow with no thought on whether a Sq. D breaker will allow a higher SCCR when used with a Siemens contactor. It will not of course, which is why they end up just putting on the 5kA "courtesy" listing for SCCR. It's not just the elevator industry that does this of course, it happens a lot with high volume OEMs all over, partly because the buyers are trained to maintain profits by keeping costs down on every individual component.

I think the long term solution is an education process that needs to take place. Engineering needs to dictate to Purchasing that they need to bundle components to get higher SCCR capabilities. But Engineering will not bother themselves with that unless Sales and Marketing tells them that customers insist on HAVING a reasonable SCCR, and customers unfortunately only find out AFTER they have already purchased the equipment and tried to install it, at which point it's too late for them.

So to that end, I wholeheartedly agree that it must be driven by the Specification process; INSIST that equipment electrical controls have an SCCR of greater than or equal to the AFC. Sales will have to investigate it, their Engineers will have to come up with a plan, then force their buyers to stop piecemeal pricing of important components.