transformers disconect req?.

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velezl

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Hi.we are installing a 30kva dry type transformer 480 to 208/120 .it is going to be located about 45f from the mdp and its going to be at a height of 12f from the floor.this transformer is require to have a disconect for sevice purpose?
 
Welcome!

No.
The primary disconnecting means can be located anywhere (in the same building).
240.21 addresses the secondary disconnect.
 
As Augie stated there is no requirement for a service disconnect on the primary of this transformer within sight. The primary condcutors will be protected by an OCPD ahead of the primary feeder wherever it originates. A local disconnect switch adjacent to the XFMR is only a design issue.

Welcome to the Forum. :)
 
Although not required, I wish they were.
Especially when cleaning out,Tightening lugs or Maintaining in any way.
Its always nice to be able to look over and see a disconnect turned off and no one around it. Generally when working with a transformer you are dealing with some fairly serious primary voltages. I never did understand why a disconnect was not required to be within sight of a transformer.
 
jap said:
Although not required, I wish they were.
Especially when cleaning out,Tightening lugs or Maintaining in any way.
Its always nice to be able to look over and see a disconnect turned off and no one around it. Generally when working with a transformer you are dealing with some fairly serious primary voltages. I never did understand why a disconnect was not required to be within sight of a transformer.
Click to expand...

Your wish may be granted.:D

There is a code proposal that has passed the proposal stage for the 2011 code cycle that would require a disconnecting means for a transformer. See ROP 9-176.

Chris
 
Here is what the ROP says:

_______________________________________________________________
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.
Click to expand...

Chris
 
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