U.L.

[Btrox]

I live in a state where everything must be U.L. listed.


I have received some OEM control panels that are marked U.L. listed, but the 3 phase feeds to these panels are to be connected from the bottom side of the main fuses. Also, some contactors are fed from the bottom instead of the top.
Has anyone else seen this?, I'm not sure if anything is wrong with that setup or just odd looking. Again, the panels are marked U.L. listed but am questioning the connections.
thx,

 

[augie47]

Are you sure the marking is akin to "Listed Industrial Control Panel" and not just a UL "Enclosure" ?
Also, IM me and I can give you a good UL contact that seems to get things done.

 

[cadpoint]

What is the wiring method? It'll come down to what type of service is presented on the circuits .

 

[augie47]

There are folks here far better equipped to address this than I, but, in the past I have encountered the same situation and found the items he mentioned to be contrary to U.L., I believe, 509. U.L had it corrected.

 

[don_resqcapt19]

Are these just fuse blocks, or are they disconnect switches with fuses. As far as I know there is no rule that say the supply has to be connected to the top of a fuse block.

 

[petersonra]

Are these just fuse blocks, or are they disconnect switches with fuses. As far as I know there is no rule that say the supply has to be connected to the top of a fuse block.

I agree. Unless the fuse block is marked line/load which a few are.

I don't recall off hand if UL508a requires feed from the top or not on a fuse block. I don't think so but I would have to look to be sure.

 

[kwired]

Top or bottom feed of many devices is often not much of an issue, fused disconnects are required to de-energize the fuseholders when the switch is opened by NEC and also likely by UL. Line side lugs do not necessarily have to be on top, but commonly are.

 

[Aleman]

That would bug me too. I don't know if the UL has a spec on the fuses or contactors. The book is around $800 so I haven't seen one. Even though fuses are traditionally fed from the top, and contactors...both would work ok backwards. But they could present a safety issue to someone trouble shooting a hot panel if they made an assumption that the bottom lugs were not live. In my opinion what you have is not right. I can't say if the UL would support my opinion.

 

[chris kennedy]

contactors...both would work ok backwards.

Many contactors are marked L1, L2, L3 and T1, T2, T3 so the could be issues there.

But they could present a safety issue to someone trouble shooting a hot panel if they made an assumption that the bottom lugs were not live.

That individual would not meet the Art 100 def of Qualified Person and probably shouldn't be working on that equipment.

 

[jim dungar]

I can't say if the UL would support my opinion.

UL would not support it.
UL requires you to follow the device if it says "line and load", other than that bottom feed is absolutely allowed. Markings like L1 and T1 are not sufficient, the device must clearly identify the Line terminals.

 

[petersonra]

Many contactors are marked L1, L2, L3 and T1, T2, T3 so the could be issues there.

I am not sure that those terminal labels qualify as line/load markings. They are just terminal identifiers like 11, 12, and 13.

That individual would not meet the Art 100 def of Qualified Person and probably shouldn't be working on that equipment.

I agree. You can't rely on the contactor contacts being open to protect you from electrical hazards. What is one of them failed stuck closed?

 

[S'mise]

I agree, feeding the line on the bottom is probably contrary to the device manufactures instructions (I have seen some German controls designed like this)

Other than that I think the NEC is mute on the matter. If this was machinery controls it would fall under nfpa79 where I believe it's not allowed.

 

[kwired]

I am not sure that those terminal labels qualify as line/load markings. They are just terminal identifiers like 11, 12, and 13.




I agree. You can't rely on the contactor contacts being open to protect you from electrical hazards. What is one of them failed stuck closed?

Sometimes a contactor doesn't open all poles of the circuit by design either, just enough to stop current flow in the controlled load.

 

[Aleman]

Many contactors are marked L1, L2, L3 and T1, T2, T3 so the could be issues there.



That individual would not meet the Art 100 def of Qualified Person and probably shouldn't be working on that equipment.

But even the most qualified people occasionally fail to grasp the concept

 

[S'mise]

Sometimes a contactor doesn't open all poles of the circuit by design either, just enough to stop current flow in the controlled load.

Exactly, there can be connections intended for a capacitor or resistor banks.