Transformer Disco

[GG]

Is a disconnect required to be within sight of a transformer that is a 75KVA with a 480V primary and a 208V secondary? The primary is landed at a junction box that supplies power to the transformer. There is no disco in sight. Also the transformer sits in an open area of a commercial kitchen where it is likely to be exposed to water that could splash on it. Shouldnt it be behind a guard to prevent water from splashing on it?

I looked at section 450 and could not find any answers to my questions.

 

[don_resqcapt19]

Transformers do not require a local or within sight disconnect. I don't see water splashing on it as an issue, but if the water could splash in a way to get on the windings, then you should look as some type of protection. Maybe a "3R" kit for the transformer. Note that the secondary conductors will require protection per the rules in 240.21(C).

 

[infinity]

There is no requirement for the primary to have a disconnecting means within sight. Your second question is not as easy since Article 450 makes no real reference to dry type transformer installed in wet locations indoors. My guess is that would be covered by the listing of the transformer itself if this indeed a wet location by definition.

 

[GG]

Thanks. Do you ever see a day when the NEC might make it a requirement for a disco to be within sight of a transformer? Seems like it would be a good idea.

 

[infinity]

Thanks. Do you ever see a day when the NEC might make it a requirement for a disco to be within sight of a transformer? Seems like it would be a good idea.

Maybe the 2011?

 

[charlie b]

Do you ever see a day when the NEC might make it a requirement for a disco to be within sight of a transformer? Seems like it would be a good idea.

Installing a local disconnect: perhaps a good idea, sometimes. Requiring a local disconnect: bad idea. Is it indeed coming in 2011: I hope not.

 

[raider1]

Maybe the 2011?

Yep, I did not see anyting in the ROC that changed Proposal 9-176 that will require a disconnecting means for a transformer in the 2011 NEC. Here is the ROP.

_______________________________________________________________
9-176 Log #3821 NEC-P09 Final Action: Accept in Principle
(450.14)
_______________________________________________________________
Submitter: James J. Rogers, Bay State Inspectional Agency
Recommendation: Add new text to read as follows:
450.14 Disconnecting Means. Transformers other than listed class 2 or class
3 transformers shall have a disconnecting means located either in sight of the
transformer or remotely provided the remote disconnect is capable of being
locked in the off position. When the disconnecting means is located remote
from the transformer the locking means required shall remain in place whether
or not the locking means is installed.
Substantiation: Requiring a disconnecting means for a transformer is intended
to enhance safety for the qualified individual that is required to work on the
transformer. This is especially true in installations utilizing the requirements of
240.21(B)(3) whereby there may be several transformers in different locations
all tapped from one feeder and it may be impractical to de-energize the entire
feeder system to work on one of the transformers.
Panel Meeting Action: Accept in Principle
Revise the rule to read as follows: ?Transformers, other than Class 2 or Class
3, shall have a disconnecting means located either in sight of the transformer or
in a remote location. Where located in a remote location, the disconnecting
means shall be lockable, and the location shall be field marked on the
transformer.?
Panel Statement: CMP-9 has made editorial changes to avoid a run-on
sentence, used ?open? instead of ?off? for the disconnect position in
accordance with customary code usage, used ?where? instead of ?when?
because it is a question of place and not time, and removed the listing
limitation on the Class 2 and 3 transformers because it has no bearing on
whether a disconnecting means needs to be installed. The lockable wording
correlates with the task group results reported in Proposal 9-201.
Number Eligible to Vote: 12
Ballot Results: Affirmative: 12
Comment on Affirmative:
YOUNG, R.: The disconnecting means should be lockable in the open
position whether or not the disconnecting means is mounted either within sight
of the transformer or in a remote location.

Chris

 

[LawnGuyLandSparky]

I just don't get the substantiation. I've never known a transformer that required future "servicing" and suspect that not a single one of the hundreds I've installed ever had their covers opened again.

 

[charlie b]

I just don't get the substantiation.

Neither do I, but for a different reason. If I designed a system with several transformers coming off the same feeder (i.e., one breaker serves all), then I would consider putting in a local disconnect, to make things simpler and perhaps safer for the future maintenance person. But I don't like having that requirement imposed on all transformers, because of this one limited circumstance. For the vast majority of situations, you have one transformer fed from one breaker, and turning off that one breaker provides enough safety for the worker.

 

[infinity]

Is it me or does just about every disconnect whether within sight or not have a means to install a lock? If so this change will really accomplish nothing.:roll:

 

[charlie b]

I think not. The HVAC disconnect commonly used in single family homes is just a removable link. The maintenance person puts the link in his tool chest while work is going on, and there is no lock placed on the disconnect itself. However, most motors that have local disconnects will have disconnect switches, and those are lockable.

 

[infinity]

I think not. The HVAC disconnect commonly used in single family homes is just a removable link. The maintenance person puts the link in his tool chest while work is going on, and there is no lock placed on the disconnect itself. However, most motors that have local disconnects will have disconnect switches, and those are lockable.

You're right about those disco's, I was actually thinking about larger 3 phase transformer disconnects. I think that just about everyone of those would have a provision for a lock.

 

[LawnGuyLandSparky]

Neither do I, but for a different reason. If I designed a system with several transformers coming off the same feeder (i.e., one breaker serves all), then I would consider putting in a local disconnect, to make things simpler and perhaps safer for the future maintenance person. But I don't like having that requirement imposed on all transformers, because of this one limited circumstance. For the vast majority of situations, you have one transformer fed from one breaker, and turning off that one breaker provides enough safety for the worker.

I've never encountered that situation. Typically, I see 480v buss duct risers feeding 480/277v core switchboards with anywhere from 1 to 6 3-phase breakers feeding 480-->208v transformers in high rises. The actual transformers are usually 1 or 2 in the core electrical closets, any more and they're usually located in tenant spaces. They're o/c protected, that's all that matters. I even question the need for o/c protection on the secondary side of the SDS.

 

[Adam A]

I \f a transformer has a melt down hopefully there is some designation of where the overcurrent protection is I personally think there should be a Knife nearby

 

[Adam A]

I had to repair the leg of one xfmr at Borders and wish it did have a disconnect nearby also was suspended 10ft above floor