dedicated space above transformers

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cbennettmegco

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An installation has four enclosed dry type transformers in an electric room. the transformers are 480 volt and the distance between the front of one unit and the rear of the next is 35 1/2 inches. The enclosures have sprinklers and ducts located within six feet of the tops of the units. The transformer doors are labeled with arc flash warning stickers which I would assume mean that the manufacturer thinks that they may be opened while energized. should these transformers have work space as required (NEC 110.26), and dedicated space above them (NEC 110.34) , or are they compliant as they are installed?
 

roger

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dcspector said:
no, no and yes to what?:-?

  1. should these transformers have work space as required (NEC 110.26)
  2. and dedicated space above them (NEC 110.34)
  3. or are they compliant as they are installed?

Roger
 

coulter

Senior Member
What is in an xfm that requires examination ... while energized.

The transformer doors are labeled with arc flash warning stickers which I would assume mean that the manufacturer thinks that they may be opened while energized.
Unless there is something really odd about that xfm, that sticker has nothing to do with the mfg thinking the working clearances of 110.26.A are required.

Charley's answer is right on target.

carl
 

coulter

Senior Member
iwire said:
IR scans are routinely done on energized transformers.
True, on some. Can't say I done any, nor been around any companies that wanted any done, on dry type less than 500kva, in the last 40 years.

Are you suggesting that one should install all equipment for what might be a future maintenance practice?

carl
 

iwire

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coulter said:
Are you suggesting that one should install all equipment for what might be a future maintenance practice?

Mostly just throwing it out there for discussion.

IR scans of building electrical systems are becoming quite common they will often be looking at 30 through 300 kVA transformers.
 

charlie b

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Much may turn on the notion of "examination," but I would say that taking IR images is not an activity for which 110.26 would require working clearance. In general, if you open a door and look inside, without putting your hand or any tool past the plane of the door's opening, you are not doing an activity addressed by 110.26. I will acknowledge, however, that I don't do any of those activities, and would therefore not be at personal risk. So I predict that one or more of you who do do such activities might disagree.
 

dcspector

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Burke, Virginia
iwire said:
Mostly just throwing it out there for discussion.

IR scans of building electrical systems are becoming quite common they will often be looking at 30 through 300 kVA transformers.

Bob, and I am sure Brian John will agree as well. When I was an EC I had to check readings, and visual maintenance while the transformer was buzzing. It is safe if all precautions are taken and very accurate readings. Proper working clearances were an issue.
 

coulter

Senior Member
dcspector said:
Bob, and I am sure Brian John will agree as well. When I was an EC I had to check readings, and visual maintenance while the transformer was buzzing. It is safe if all precautions are taken and very accurate readings. Proper working clearances were an issue.

Let me see if I translated correctly: 110.26.A applies to transformers because someone may choose to remove the covers to perform an visual inspection from a few feet away. Did I get that right?

Assuming I did get it right, Bob's nor Brian's opinion on this issue concern me. The only opinion that would concern me is the, "My way cause I said so" inspector You know, the one that makes up code cause that's the way they think it should be.

Now, what size xfm do you want 110.26.A to apply? Bob says down to 30kva. Do you have a lower limit?

carl
 

dcspector

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Location
Burke, Virginia
coulter said:
The only opinion that would concern me is the, "My way cause I said so" inspector You know, the one that makes up code cause that's the way they think it should be.



carl

I am not exactly sure how to take that........personal?:confused: I hope that was not directed at me!
 

don_resqcapt19

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coulter said:
Now, what size xfm do you want 110.26.A to apply? Bob says down to 30kva. Do you have a lower limit?
carl
As the code section is now written it prohibits the countertop receptacles that are required by 210.52(C). In other words the current wording is all inclusive. This section needs work, but the CMP refuses to acknowledge that fact.
 

iwire

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coulter said:
Now, what size xfm do you want 110.26.A to apply? Bob says down to 30kva. Do you have a lower limit?

Carl all I am saying is IR scans are something to consider and I do not have a lower limit.

One of my coworkers spends a lot of time doing IR scans of electrical systems in many types of occupancies. stores, factories, office buildings, health care buildings etc.

I think that 110.26 is very subjective and we can not really provide a national answer to what it covers and does not cover. It is my opinion that as written much is left to the inspectors discretion. As Don pointed out counter receptacles are in conflict with 110.26 and as I often point out disconnect switches above suspended ceilings are often in violation of 110.26.

It's a real word out there and inspectors do have to make judgment calls with many code sections. :smile:
 

cschmid

Senior Member
I guess that if thermal imaging is a possibility then yes 110.26 (a) say yes it applies..if the transformers have doors that open then I would assume they were installed for thermal imaging..

I will also assume the style of transformer described would be energized and never turned off unless some sort of maintenance was required such as to verify lug tightness..

so you are saying 35 1/2" is your distance and 36" is the required distance..I can see the dilemma with the 1/2"..I have been in business for almost 30 years and I can not remember ever having thermal images of a dry transformer..Yet does the manufacture state that should be a consideration in the life of the transformer..
 

coulter

Senior Member
iwire said:
...It's a real word out there and inspectors do have to make judgment calls with many code sections.
The following is strictly my personal opinion - certainly not aimed at dc personally - but is aimed at all inspectors who use "life experiences" to make technical code decisions:
And I see this as a problem. Consider this:
Electrical room is complete, inspector shows up, measures space around the transformers:
Inspector: "Clearances don't meet 110.26.A."

Contractor says, "It matches the stamped prints exactly. What in that transformer do you think needs examination ... while energized?"

Inspector: Well, when I was a contractor I was hired to do thermal scans of similar transformers. And that to me is "examination while energized".

Contractor: Nothing in the prints about future maintenance practices. And I also don’t see anything in the NEC about future maintenance tasks.

Inspector: I’m telling you my judgment is these transformers fall under 110.26A.

Contractor: Okay. We need some written criteria of which transformers fall under your judgment call. This building has transformers ranging from 1000kva to 50va. Which are in and which are out? And it would be nice if the AHJ were consistent for the next project. And if this is going to become a minimum design spec, how about the AHJ publish so we can all meet it during the design phase, not during the “job is finished inspection” phase.

bob and dc –
This above conversation is my translation of what you two are advocating. The NEC is a set of minimum design specs. After meeting those minimums, the rest are design decisions. The inspectors judgment call on installation criteria to meet unspecified maintenance practices should be of no consequence – unless the inspector falls under the, “cause I said so”

carl
 

dcspector

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Location
Burke, Virginia
Carl.....point taken and I understand what you are saying now. No I do not Inspect that way otherwise I would not be on this Forum. It's an off color area with Transformers.....yeah I enforce the working clearance and never had a problem due to the EC's in DC have the working clearance.
 
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