Questions concerning my first transformer and the service feeding it

[mark32]

Hey! Aside from him mentioning the inrush current upon startup, it seemed like he was reading from tables, perhaps, that they have at their disposable during these calls. Like, he knew up front that the primary ocpd for the 30kva transformer in question is suppose to be 110 amp. He didn't say, "Well, if we look at article 450 and add 125% to the primary current of 83 amps, that brings us to103 amps and then blah blah blah". He didn't go into any theory as to why he didn't like me going with the 15kva transformer either, but he was confident in his answers

 

[hillbilly1]

Just an update, I called tech support for Acme transformer (That's who my supply house deals with) and their guy favored the 30kva transformer over the 15kva for my application, and he also recommended a 110 amp breaker for the primary as opposed to a 100 amp breaker that I had intended on using. While online, I came across Maddox transformers, and their price was much better than the Acme. Anyone familiar with Maddox?

I’ve used Maddox before, so far, I haven’t had any issues, and they are pretty quick at getting it to you.

 

[MD Automation]

I’ve used Maddox before, so far, I haven’t had any issues, and they are pretty quick at getting it to you.

Agreed - have certainly heard of Maddox.

Can also look at Hammond transformers (HPS).

Obviously Eaton and Square D as well.

 

[hillbilly1]

I’ve got two 45 kva single phase units in service for over two years now, very quiet, and idle current is about a half amp.

 

[mark32]

Thanks guys, my buddy just placed the order for the Maddox

 

[mark32]

Hey bros,

The transformer arrived and I have a question. There are two single hole lugs on H0 (Again, this is 208v delta to 480/277 Y) So, one lug for the grounded conductor, and one for the gec, but don't I need a third lug so as I can bond the enclosure to H0? I noticed the supplied ground bar only has two openings, however, there is a copper strap that this ground bar sanwhiches to the enclosure. This strap in turn, is bonded to the base the windings sit on. Perhaps H0 is bonded to the enclosure via this strap? Also, there are no ko's that appear to be made to enter the enclosure for the gec. I don't have a problem making my own ko, but what do most installers do for the gec, just run it through the grate on the bottom? I will consider the gec to be subject to physical damage in this location, therefore, I would like to sleeve it in some sort of raceway.

 

[mark32]

I'd like to run the gec to this beam

 

[ActionDave]

The iron core for the transformer windings sits on some rubber pads to make the transformer quieter, the strap bonds that to the transformer case.

I would change the lugs on the HO to a three holer. You could also run your system bonding jumper from the HO to a two or three hole lug and bond that to the transformer case and run your GEC from there to the building steel. I wouldn't worry about sleeving it but if you must non metalic flex is a common method, although it's just window dressing no matter what the sleeve is composed of. Make KOs as needed. There is usually a sticker inside telling you not to make any holes above it.

 

[mark32]

Thank you Dave, I appreciate it!

 

[Strathead]

I'd like to run the gec to this beam View attachment 2564625

As long as the beam is tied to the rebar under the slab, it will be perfect.