Disconnect Switches with 5 ungrounded conductors- Separate Disconnects? 1

[Eng8492]

We have a piece of equipment with 480V 3phase (no neutral) and 240 L1/L2 running into it for a total of 5 wires. Isn't there some rule that you have to break all 5 ungrounded conductors with one disconnection switch, instead of having one switch for the 240V and another switch for the 480V? Seems to me it should be common sense....

 

[controlsdude]

So the 480vac feeds a step down transformer 480/240 this then goes to the machine with the 480. So really you have a disconnect before the transformer that breaks 480 also to the machine. So your saying your breaking 480v only?

Usually see this as the case 480vac disconnect, not a disconnect with 5 wires which is special.

 

[Eng8492]

No step down transformer. There is 240VAC going into our machinery for one thing and 3 phase 380-480VAC for something else. They are provided from the infrastructure so 5 ungrounded conductors go into the machinery.

 

[DRWeig]

I don't see a need for a single switch.

When we build UL panels, we're just required to label them thus:

55.4 An industrial control panel intended to be provided with more than one supply source such that more
than one disconnect switch is required to disconnect all power within the control panel shall be marked
with the word ²CAUTION² and the following or equivalent: ²Risk of Electric Shock – More than one
disconnect switch may be required to de-energize the equipment before servicing.²


Best to you,

Goober Dave

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[itsmoked]

Nice info Dave.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jraef]

That's the simplest solution, however you can easily get a 6 pole disconnect switch and only use 5 of the poles, they are used typically for 2 speed 2 winding motor disconnects.

"Will work for (the memory of) salami"

 

[Eng8492]

Thanks for the info Dave. We'll consider using a sticker.

I found another solution while I was away--- alot of companies make linkages that can join two 2pole or 3pole switches. 5p and 5p switches exist but are rare.

 

[DRWeig]

Look into the 6-pole that jraef mentioned. They're more common than 5-poles, would be easier too find and less expensive.

Here's an example: Eaton 6-Pole Safety Switch


I agree that a single switch makes a safer product, but it's not a requirement.



Best to you,

Goober Dave

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