110.26 & 110.34

[m sleem]

I have utility building including many 13.8kv transformers, the existing arrangement like the 13.8kv side of transformer-a opposite to the 400v side of transformer-b then i have to follow 110.34 accordingly maintain min 2.8m distance between transformer a&b, if i rearrange the transformers so that the 13.8kv side of transformer-a opposite to the 13.8kv side of transformer-b & the 400v side of transformer-b opposite to the 400v side of transformer-c, can i follow 110.26 accordingly maintain min 1.2m??

 

[Carultch]

I have utility building including many 13.8kv transformers, the existing arrangement like the 13.8kv side of transformer-a opposite to the 400v side of transformer-b then i have to follow 110.34 accordingly maintain min 2.8m distance between transformer a&b, if i rearrange the transformers so that the 13.8kv side of transformer-a opposite to the 13.8kv side of transformer-b & the 400v side of transformer-b opposite to the 400v side of transformer-c, can i follow 110.26 accordingly maintain min 1.2m??

When multiple voltage categories are present in the "common aisle" situation, you have to follow the spacing for the higher voltage.

I see it as a real stretch of the rules to spin a transformer 180 degrees, and stagger them so that only the secondary cabinets are 4 ft apart with empty space opposite the primary cabinet. It is my understanding that workspace has to be 30" or the width of the equipment. So once a workspace applies to the primary cabinet, it applies to the full transformer width.

 

[m sleem]

Thanks


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[infinity]

Does the 400 volt transformer require any work space or is it just treated as a grounded surface when measuring the work space from the 13.8 trans?

 

[petersonra]

I have utility building including many 13.8kv transformers, the existing arrangement like the 13.8kv side of transformer-a opposite to the 400v side of transformer-b then i have to follow 110.34 accordingly maintain min 2.8m distance between transformer a&b, if i rearrange the transformers so that the 13.8kv side of transformer-a opposite to the 13.8kv side of transformer-b & the 400v side of transformer-b opposite to the 400v side of transformer-c, can i follow 110.26 accordingly maintain min 1.2m??

I would say that as long as the primary and secondary are completely separate the answer is yes if you want a code answer.. My guess though is that a lot of people would not like it.

Take a look at what table 110.26(A)(i1) actually says.

It refers to exposed live parts. So I don't see how if the only exposed live parts are less than 600V that 110.34 would apply.

Table 110.34(A) has similar wording. It refers to exposed live parts over 600V. I don't see how it could apply if there were no exposed live parts that exceeded 600V.

 

[Carultch]

Does the 400 volt transformer require any work space or is it just treated as a grounded surface when measuring the work space from the 13.8 trans?

It is my understanding that you can properly label your equipment, and take credit for a dead front closed piece of equipment to be a grounded metal surface, provided that it is marked to indicate not to service both pieces of equipment simultaneously, and there is no reason to service both simultaneously. So if the door on one unit remains closed while working on the piece across the aisle, and it is sufficiently labeled to indicate so, then you can have the condition 2 workspace.

 

[m sleem]

I would say that as long as the primary and secondary are completely separate the answer is yes if you want a code answer.. My guess though is that a lot of people would not like it.

Take a look at what table 110.26(A)(i1) actually says.

It refers to exposed live parts. So I don't see how if the only exposed live parts are less than 600V that 110.34 would apply.

Table 110.34(A) has similar wording. It refers to exposed live parts over 600V. I don't see how it could apply if there were no exposed live parts that exceeded 600V.

Petersorna,
it's the same case as panels, all live parts are enclosed in panel housing.

 

[m sleem]

Does the 400 volt transformer require any work space or is it just treated as a grounded surface when measuring the work space from the 13.8 trans?

Boss, i meant by 400v the transformer side, but it's still 13.8/0.4kv.