UL508A FLA for Lighting Control

[RiseFromYourGrav]

Good afternoon,

I work for a electrical equipment manufacturer, and every once in a while we get a UL508A control panel. This particular one is a simple one, just a mechanically held lighting contactor (ASCO 918 with 3 wire control) and a switch for it. I need to label the FLA as per UL 508A 49.2 and...I get almost nothing. So I say it's 1A. The coil only draws when switching states, but the 3-wire control pulls 2VA I guess.

My boss, however, is of the opinion that I should include the lighting loads that are controlled by the contactor in this calculation. It's a 6P 30A contactor, so there could be (6) 30A lighting loads going through it, and we have terminal blocks in there so the contractor can easily enter and exit. What's the right thing to say on the nameplate? 1A? 30A? 180A? 5A (the fuse size)?

 

[petersonra]

You are required to show the FLC of each of the sources wired to the box.

So it could be six 30 A, and one 1 A.

Or one 181 A.

However, it might also be that they are intended to be used on a three phase wye output so maybe it is 61 A.

Sort of depends on how you show the power wiring.

 

[Jraef]

You are required to show the FLC of each of the sources wired to the box.

So it could be six 30 A, and one 1 A.

Or one 181 A.

However, it might also be that they are intended to be used on a three phase wye output so maybe it is 61 A.

Sort of depends on how you show the power wiring.

Would you add up the separate 30A circuits for this? I would interpret it as 30A, no matter how many poles the contactor has. The way UL508A states it is that you must show the maximum current of each source of supply.

49.1 The input terminals intended to be connected to each source of supply shall be rated in volts, total
full-load amperes, ampere or horsepower rating of the largest motor (when multiple loads are controlled),
number of phases when other than single phase, and the frequency.

Then:

52.1 An industrial control panel shall be provided with a nameplate marking that includes the following:
a) Manufacturer’s name or authorized designation;
b) Complete electrical rating of each source of supply as specified in 49.1;
...

You cannot bring in a 180A source of supply directly to the contactor line terminals and split it out to the 6 poles, you would need to have another device like a splitter block that is rated for 180A. So if there is no splitter block, the nameplate should say "30A at xxxV, up to 6 separate circuits."

Nobody pays any attention to control power sources on the UL nameplate, unless it's significant.

 

[petersonra]

It seems to me the word "each" suggests the marking requirement has to have all the supplies listed. I think your idea of calling it (6) 30 A supplies would be sufficient to meet this requirement if they were all separate.

As for the control circuit, the rule says this.



So if there is a control transformer it needs to be included.

 

[Jraef]

...
So if there is a control transformer it needs to be included.

Yes, but if it’s a 240V primary and a small 50VA CPT, 0.2A primary current is a rounding error.

 

[petersonra]

Yes, but if it’s a 240V primary and a small 50VA CPT, 0.2A primary current is a rounding error.

I think there is a rule that you have to round up if it is over 0.5 and down if it is under 0.5.