Control Panel SCCR & Marking

necnotevenclose

Senior Member
I'm working on a project that is adding a skid that has a control panel. I was able to physically look at the control panel and did not see the SCCR rating listed. I contacted the company and was told the SCCR marking is on the the inside cover of the control panel per UL 508A. As a side note, this control panel contains more than just control componets. I was told by the manufacture the SCCR rating is 5kA. I ran a fault study and came up with 20kA.

So it appears to me there are two issues:

1) The marking between UL 508A and 2008 NEC 409.110 does not match.
2) My calculated AFC is higher than the CP SCCR.

Per local AHJ I'm not able to provide current limiting fuses and I would rather not have to add additional conductor length to reduce AFC.

So I'm I viewing this wrong, if not are there any other options to reduce AFC?
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
1) There is no conflict between UL508A and the NEC. UL says it's OK to put the information on the inside of the door, the NEC says if it is NRTL listed it's OK. The labeling per 409.110 would apply if you were NOT using an NRTL listed assembly and determined the SCCR by another means.

2) You could add a transformer or other inductor with enough impedance to bring your AFC down to 5kA.

Such is the problem with a lot of UL508A shops that technically follow the rules, but have no concern for the installation consequences of just settling on a 5kA SCCR rating, the "no-brainer" option. Hopefully after a few gut wrenchers like this, people will start to investigate in advance what SCCR level will be necessary for an installation and insist to the panel shops that they provide a panel that meets the requirements in the field. UL would have let the panel shop do it with CL fuses, then once again, after they apply the NRTL sticker, you are good to go regardless of the AHJ's predilections.

In fact that may be another option, send the panel back to the shop and have them redesign it to put a 20kA SCCR label on it.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I get a kick out of people who blame the control panel shop for this problem. It adds cost to have a higher SCCR and people just won't pay for it. That is the reason people get the cheapest option.

I used to work for a place that did water treatment systems. We would specifically ask people to select options for available flow, pressure, and drain arrangements that the site had and include pricing for the various options. Inevitably a few customers would select the cheapest price and it would not work.

We even had a customer one time that bought a system that used chemicals he did not have access to because it was cheaper than a system that used the chemicals already there.

We had a place once that bought a system with an option for a steam heat exchanger because it was cheaper than the option for a system with an electric hot water heater. You might guess that there was no steam available anywhere near where the equipment was located and an electric hot water system had to be expeditiously added in the field.

When people look at the dollar signs, they often do not see anything else.
 
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