Clearance Requirements for Dry type transformer for 150 kVA

[Cherwin Baga]

I’m trying to find out the required code clearances for dry type transformer. I have a 150kVA dry type transformer. The transformer is ultra efficient type and class 220 C. The nameplate of the transformer indicates ventilated surfaces must have at least 2 in clearance. I looked at 450.21Band determined that the transformer falls under exception 2, but the required clearance is not clear to me. The room that I plan to install the transformer has a dimension of D=37 in, W= 60 in, L = 164 in. The transformer dimensions are D = 23 in, W = 33 in, L= 38 in. Can someone please point me to the specific NEC code clearance requirement?

 

[Buck Parrish]

I’m trying to find out the required code clearances for dry type transformer. I have a 150kVA dry type transformer. The transformer is ultra efficient type and class 220 C. The nameplate of the transformer indicates ventilated surfaces must have at least 2 in clearance. I looked at 450.21Band determined that the transformer falls under exception 2, but the required clearance is not clear to me. The room that I plan to install the transformer has a dimension of D=37 in, W= 60 in, L = 164 in. The transformer dimensions are D = 23 in, W = 33 in, L= 38 in. Can someone please point me to the specific NEC code clearance requirement?

The engineers tend to make the rooms to small

 

[Cherwin Baga]

it's an old building built in the 70s.

 

[ron]

110.26 shows the working space that is needed in front of the energized access panels. Place that so the door to the closet makes up the needed working clearance.

 

[Cherwin Baga]

so in addition to the background, there is an existing transformer in this closet and I plan to replace it with the ultra efficient unit. the dimensions of the existing transformer are D = 16 in, W = 34 in, L= 47 in. and currently it's mounted about 9' above finish floor. as for 110.26, does the working space apply in this case? We do not plan to access this equipment energized. And the primary disconnect is accessible meeting 110.26.

 

[ron]

so in addition to the background, there is an existing transformer in this closet and I plan to replace it with the ultra efficient unit. the dimensions of the existing transformer are D = 16 in, W = 34 in, L= 47 in. and currently it's mounted about 9' above finish floor. as for 110.26, does the working space apply in this case? We do not plan to access this equipment energized. And the primary disconnect is accessible meeting 110.26.

When PM is done, IR scanning gets done while energized. Most AHJ's consider the front accessible side of the XFMR to require working clearance per 110.26

 

[augie47]

When PM is done, IR scanning gets done while energized. Most AHJ's consider the front accessible side of the XFMR to require working clearance per 110.26

That's interesting. None of the inspectors in this area address 110.26 on transformers as they don't see them as being worked on while energized. The IR scan requirement sheds new light on that thinking although I can't imagine removing the cover while energized on most transformers I've worked on

 

[ron]

That's interesting. None of the inspectors in this area address 110.26 on transformers as they don't see them as being worked on while energized. The IR scan requirement sheds new light on that thinking although I can't imagine removing the cover while energized on most transformers I've worked on

If you remove the cover energized or de-energized, how does that impact whether you are in front of energized parts while IR scanning which is done energized?

 

[augie47]

If you remove the cover energized or de-energized, how does that impact whether you are in front of energized parts while IR scanning which is done energized?

I understand...... the EI here haven't taken that into consideration as of yet