Question about disconnects for Transformers

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JJWalecka

JJWalecka

Senior Member
Location
New England
I wanted to know if the disconnecting means for a Dry-type Transformer less than 600V nominal had to readily accessible. I read in 450.13 that all Transformers and Transformer vaults shall be readily accessible to qualified personnel for inspection and maintence or shall meet the requirements of 450.13 a or b. 450.13a states that Dry-Type transformers 600V nominal or less located in the open on walls, columns, or structures, shall not be required to be readily accessible. Where does it state in the NEC the requirements for the accessibility of the disconnecting means. Thank you for your time and effort.
 
Re: Question about disconnects for Transformers

Do you need a disconnect if so why??

Maybe you could provide some additional information.

there are a number of locations that will require location and height restrictions for a disconnect.

110.26 404.8, I am not aware of a requirement in article 450 that a transformer must have a disconnect with in a certain location or height. 240.21 (B) 3 and section (C)1-6 may cause a fused disconnect to be installed if so the articles I mentioned will impact the location of such a disconnect.

If the disconnect contains fuses article 240 may have some requirements for their locations.


Hope this helps

Charlie
 
Re: Question about disconnects for Transformers

The reason I'm asking is the Dry-Type Transformer less than 600V nominal is mounted on the structure decking at about thirty feet. The cutout box is located at about twenty feet. There is a disconnect pole to close the circuit feeding the Transformer. I questioned the hieght because I thought that it would have to be readily accessible.
 
Re: Question about disconnects for Transformers

OK so your asking about an existing installation, I still think you are all set.

Here is the general requirement for switches.

2002 NEC
404.8 Accessibility and Grouping.
(A) Location. All switches and circuit breakers used as switches shall be located so that they may be operated from a readily accessible place. They shall be installed so that the center of the grip of the operating handle of the switch or circuit breaker, when in its highest position, is not more than 2.0 m (6 ft 7 in.) above the floor or working platform.
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But there are exceptions and this one should fit your installation.

Exception No. 2: Switches and circuit breakers installed adjacent to motors, appliances, or other equipment that they supply shall be permitted to be located higher than specified in the foregoing and to be accessible by portable means.
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Re: Question about disconnects for Transformers

IWire has quoted good applications for switching locations a third exception to 404 will allow hook sticks.

Also if the installations is existing and has not been cited as a violation (NEC or LOCAL whatever)
then there would seem to be little urgency to ,modify the installation.

But!

I have a question regarding the cutout box

From Art. 100 Def. Cutout Box. An enclosure designed for surface mounting that has swinging doors or covers secured directly to and telescoping with the walls of the box proper.

If there are OCPD in this enclosure a 20' height above the work platform may not comply with current Code requirements.

It's just an interesting Code issue.

Charlie
 
Re: Question about disconnects for Transformers

Originally posted by cpal:
If there are OCPD in this enclosure a 20' height above the work platform may not comply with current Code requirements.
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Charlie, Which requirement would that be? :confused:

Bob
 
Re: Question about disconnects for Transformers

Bob
I was thinking outloud, but if the cutout box is installed to provide OCP for the secondary tap conductors, 240.24 may apply for accessibility.

Granted I don't have a picture. Whats your thinking??

Charlie
 
Re: Question about disconnects for Transformers

Your right we don't have a picture and I find when an installation is described we all have a very different image in our minds of what it looks like.

Usually I think that image relates to a job we have done ourselves.

I know that is the case with me so I may be off track here. :)

I was thinking 240.24 also.

2002 NEC
(4)For overcurrent devices adjacent to utilization equipment that they supply, access shall be permitted to be by portable means.
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[ February 13, 2005, 09:46 AM: Message edited by: iwire ]
 
Re: Question about disconnects for Transformers

Bob.

The OP stated
There is a disconnect pole to close the circuit feeding the Transformer.
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Although where these conductors appear to be out side they can travel for distance w/o OCP per 240.21 (C) (4).

If the cutout box contains OCPD, is it your opinion that OCPDs protecting transformer secondary tap conductors (presumed) and 20' above a work platform complies with 240.24 (A) (4)??

Charlie
 
Re: Question about disconnects for Transformers

I am assuming that the cut out was on the primary side of the transformer.

There is a disconnect pole to close the circuit feeding the Transformer.
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If that is the case I believe 240.24(4) is applicable.

If the cut out is on the secondary side of the transformer that is a sticky issue. :(

But we do that a lot, if your in line at an Home Depot you will probably see a transformer hung from the ceiling along with a fused disconnect protecting the secondary conductors as the drop down to the wall mounted panel is to far to run without OCP.
 
Re: Question about disconnects for Transformers

iwire it is funny that you mentioned Home Depot. I am remodeling a Home Depot and thats where I saw the discrepancy. We are not scheduled to change it. I was just wondering if it was appropriate to have the cutoff box at that hieght. I'm sorry that I didn't describe it better. The cut off box is for the secondary also, I believe. I appreciate everyones input.

Thank you,
Justin J. Walecka
 
Re: Question about disconnects for Transformers

Originally posted by justinjwalecka:
iwire it is funny that you mentioned Home Depot. I am remodeling a Home Depot and thats where I saw the discrepancy.
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Shoot we may have done the installation. :roll:
 
Re: Question about disconnects for Transformers

iwire, I know that it was on the print spec. to install it that way. When I first saw it I thought that the cutout bow should have been readily accessible. I couldn't find a specific article that stated that it was wrong. Maybe I'm wrong in thinking it is too hieght. It would definitely keep only qualified individuals from maintaining it. I just thought in the case of an emergency that it should be readily accessible. I appreciate your input. Thank you for your time and effort.

Justin J. Walecka
 
Re: Question about disconnects for Transformers

Justin I think you and Charlie are correct and the fact it is designed, installed and passed that way does not make it right.

I can find nothing in the code that allows it.

240.24 Location in or on Premises.
(A) Accessibility. Overcurrent devices shall be readily accessible unless one of the following applies:
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None of the 'following' applies. :(

The OCP is not supplying the transformer so it must be readily accessible.

Accessible, Readily (Readily Accessible). Capable of being reached quickly for operation, renewal, or inspections without requiring those to whom ready access is requisite to climb over or remove obstacles or to resort to portable ladders, and so forth.
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Looks like something to bring up next time I see it on the prints. :eek:
 
Re: Question about disconnects for Transformers

iwire, I feel a little better now that I know I'm not the only one who couldn't find it. Thanks

Justin J. Walecka
 
Re: Question about disconnects for Transformers

I've been away for a while Valentines Day Tomorrow, don't forget!!!


Well I see we all see the same issue with the OCP, I'm not very fond of HD

Charlie
 
Re: Question about disconnects for Transformers

You cannot blame HD, but the installers and the inspector(s).
I inspected a National Chain Store a couple of weeks ago and violated the final inspection due to a wiring method they used. A long story short, the engineer told me they wired 200 stores that way this past year - my response was I only inspected the one ;) , they changed the wiring.
 
Re: Question about disconnects for Transformers

Sorry Pierre

I was just thinking out loud, I'd rather small hardware stores I'm not fond of the one size does all.But that would be an issue for another forum! No??


Charlie
 
Re: Question about disconnects for Transformers

Charlie there is no reason to be sorry, as this forum allows us all to voice our opinions :cool:

I am also like you, as I like the small town Hardware store that gives good advice and knows who I am when I come in the store. Big Box stores do have the advantage of being open alot more hours, especially when you are short a washer for that leaky sink on saturday afternoon, 5 minutes after the local hardware store just closed.
 
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