Needs additional disconnect(s) or not?

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Brinkmann

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We have a customer who is starting to build self contained environmental remendiation trailers for use in Florida. These trailers are similar to the ones you see the lawn maintenance guys use. Inside the trailer will be a compressor, vacuum pump and a couple of liquid pumps. Most of the time they are in a hazardous zone.

The control panel we manufacturer goes on the trailer front(outside) and is a NEMA 4 enclosure (outside the zone). On our panel we have a main dis-connect with a thru door operator made by ABB. This dis-connect is lockable in the off position (padlock). Is our customer required to have dis-connects at each unit inside the trailer ? Most of the time he passes inspection without them. But he has a couple of times in which he had to put dis-connects at the units. Are the additional dis-connects really required the code?

Thanks in advance
 
Re: Needs additional disconnect(s) or not?

What I am asking are you using rubber cord with plug and an outlet at the power pole?

Or are these units hardwired?

If the trailers are are hardwired with a feeder you need to follow the rules in 225

225.31 Disconnecting Means.
Means shall be provided for disconnecting all ungrounded conductors that supply or pass through the building or structure.
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and you will need a ground rod at the trailer.

250.32 Two or More Buildings or Structures Supplied from a Common Service.
(A) Grounding Electrode. Where two or more buildings or structures are supplied from a common ac service by a feeder(s) or branch circuit(s), the grounding electrode(s) required in Part III of this article at each building or structure shall be connected in the manner specified in 250.32(B) or (C). Where there are no existing grounding electrodes, the grounding electrode(s) required in Part III of this article shall be installed.
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If the units are fed with rubber cord the cords must plug in at the power pole. 400.7(B)

That plug may serve as the disconnecting means.

What you are doing really IMO skirts the edge of the NEC.

You are wiring a structure in one location and bringing it to another location. Most times this means the the unit should be listed as a whole by an NTL. Otherwise wherever it is installed the local inspector has a right to inspect it.
 
Re: Needs additional disconnect(s) or not?

Look at 430.102(B). Unless your customer meets the exceptions, a disconnect will be required at each motor.
Don
 
Re: Needs additional disconnect(s) or not?

So.....from 430-102 (b) Exception..."A disconnecting means, in addition to the controller disconnecting means as required in accordance with Section 430-102 (a), shall not be required for the motor where the disconnecting means for the controller is individually capable of being locked in the open position"

IF
A)The controller has a lockable disconnecting means (ABB disconnect switch) within sight of itself. (it's on/in the main control panel)

Then
B)An individual disconnect is not required at each motor.

Sound right? and thanks to all that helped
 
Re: Needs additional disconnect(s) or not?

Actually a very good argument can be made that mobile equipment is not covered under the NEC. One of our customers has made this argument a number of times quite sucessfully after presenting his argument to those arguing otherwise.

Think about it this way - is a trailer with a compressor mounted on it covered by the NEC?

On the other hand, I think your own sense of preservation in this litigious world, and good practice would make you want to follow the "normal" conventions. Plus a lot of times it is convenient to have a way to lock out a single piece of equipment without having to get all of them.

And especially in a hazardous area, one would be inclined to be cautious about making the installation as safe as possible.

I am curious about one thing though - if the area is classified, how do you get by with NEMA 4 equipment?

<added>
I see it is only classified inside the trailer.

The other argument you can make is that it's a temporary installation. This makes a lot of sense if it really is, but if it is going to sit there for 5 years, it's pretty hard to claim temporary.

It's also hard to claim temporary if you sink a ground rod and hard wire it to the pole.

[ April 18, 2005, 04:20 PM: Message edited by: petersonra ]
 
Re: Needs additional disconnect(s) or not?

Originally posted by petersonra:
Actually a very good argument can be made that mobile equipment is not covered under the NEC.
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That is what I was trying to point out.

Although I also agree following the 'normal' procedures can only benefit the installer if the stuff hits the fan.
 
Re: Needs additional disconnect(s) or not?

Bob hit on my same concerns. Remediation systems are virtually always Class I, Group D and with the enclosed system, most likely Division 1.

With regard to Bob's client; I'd sure love to hear the argument. The compressor may not be under the NEC, but any electrical auxiliaries are. See 90.2(A)(3).

Edit Add: "Mobile" does not equal automobile.

[ April 18, 2005, 04:26 PM: Message edited by: rbalex ]
 
Re: Needs additional disconnect(s) or not?

Bob A. as I had said earlier I think this skirts on the edge of the NEC.

If we say the wiring in this trailer is covered by the NEC, permits and inspections should come from the locality that the trailer will be used at, not where the trailer is built.

This would mean it should be inspected in each locality it is moved to.

Consider that the rules where it was built may not meet the rules where it is moved to.

OR

It should be built and then 'listed' by an NTL.

I do not think this is a clear cut issue. :confused:

JMO, Bob
 
Re: Needs additional disconnect(s) or not?

Originally posted by rbalex:
Bob hit on my same concerns. Remediation systems are virtually always Class I, Group D and with the enclosed system, most likely Division 1.

With regard to Bob's client; I'd sure love to hear the argument. The compressor may not be under the NEC, but any electrical auxiliaries are. See 90.2(A)(3).

Edit Add: "Mobile" does not equal automobile.
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90.2(A)(3). Installations of conductors and equipment that connect to the supply of electricity.

Despite the seemingly wide ranging language that this subsection has, taking it in the full context of the whole section might well lead to another conclusion. For instance, quite clearly there is electricity hooked up from a semi to its trailer, yet NEC does not apply, despite that fact that such an arrangement is not specifically exempted by the paragraph.

I do agree that it is usually far easier to just go along with with the inspectors as usually the minor differences in what it costs you not to follow the "normal" rules is not worth the headaches if someone gripes about it down the road.

I have a hard time with the argument that all the equipment would have to be listed as a whole to avoid local inspection. In reality, they can hassle you to death regradless of whether it's listed and no NRTL is going to list such a piece of equpiment anyway. It's usually better to just go along with iispection to avoid the nitpicking that happens if you fight city hall.
 
Re: Needs additional disconnect(s) or not?

Brinkman,
You can use the exception to omit the disconnect within sight of the motor only if you meet one of the following conditions.
(a) Where such a location of the disconnecting means is impracticable or introduces additional or increased hazards to persons or property
(b) In industrial installations, with written safety procedures, where conditions of maintenance and supervision ensure that only qualified persons service the equipment
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Don
 
Re: Needs additional disconnect(s) or not?

Gentlemen,

As far mobile equipment or not being covered, remediation trailers are covered or built to UL PQVJ, a catch all if you will for "Mobile Units for Commerical Use." This standard directly references the NEC for guidance.

All of you are right in respect to the systems being in a hazardous zone. Our control panels are certified under UL698A, "Intrinsically Safe" and being outside the hazardous zone we can use a NEMA 4 enclosure. (with the proper sealoffs)

As far as cost and the actual reason for this thread. Explosions proof disconnects are fairly expensive when you look at 20 HP 230/3/60 motors. Generally there are 3-4 motors in the trailer.(20 HP down to 1 HP)

This industry has become extremely competitive and adding something which is not technically required can and will make the difference in the bid results.

And mostly I understand the ability of the local inspector to interpret the code as they see it.

I was hoping there was a clear cut answer to this situation but appears there is not.
 
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