KVA req's

[jnsane84]

I'm sure I already know the answer as it has been confirmed by several L.E.C. already but I really trust you guys and respect you highly so I want to present the issue to you. Recently my company purchased a large bridge mill machine from another company. Upon going to their facility to assess the project I noticed that the machine called for 112KVA. After tracing everything back I found that they had wired this machine through 4 disco's through a sub panel out to a 112KVA Xformer. Inside this subpanel are an additional 8 20A breakers. Now that the machine has been shipped to our facility one of our maint. guys has convinced our super. that we needed this crazy setup so that we can run several items from this subpanel. Am I correct in my understanding that if the machine calls for 112KVA feed and the transformer is 112KVA this is all that can be run or am I missing something?

 

[bob]

Since you are completely rewiring the machine at you location, connect it to a feeder directly from the transformer. Tell these guys to get their power from some where else.

 

[mivey]

Sounds like you might need a bigger transformer.

Not sure why there are 4 discos. The subpanel may or may not be big enough, depending on the loads in it. You did not specify the voltage, the panel size, or the existing load.

 

[charlie b]

I also do not understand the "4 discos" bit. Please don't tell me that from the subpanel, in addition to the other breakers, you have four independent disconnect switches, one per phase and one for the neutral, feeding the bridge mill machine.

As to the legality of using a 112 kVA transformer (I am betting it is actually 112.5!) to serve a machine that calls for 112 kVA plus a host of other loads, it is probably not legal. No component can be called upon to serve a greater load than its "calculated load." In your case, the calculated load would include the bridge mill machine at 112 kVA, and 180 VA for every receptacle powered by the other 20 amp circuits. It could be close, but I am guessing that a 112.5 kVA transformer will not be enough.

 

[iMuse97]

I'm sure I already know the answer as it has been confirmed by several L.E.C. already but I really trust you guys and respect you highly so I want to present the issue to you. Recently my company purchased a large bridge mill machine from another company. Upon going to their facility to assess the project I noticed that the machine called for 112KVA. After tracing everything back I found that they had wired this machine through 4 disco's through a sub panel out to a 112KVA Xformer. Inside this subpanel are an additional 8 20A breakers. Now that the machine has been shipped to our facility one of our maint. guys has convinced our super. that we needed this crazy setup so that we can run several items from this subpanel. Am I correct in my understanding that if the machine calls for 112KVA feed and the transformer is 112KVA this is all that can be run or am I missing something?

1. you do already know the answer.
2. it is being confirmed by even more people, now.
3. don't compromise a large piece of expensive equipment so that someone can avoid a little extra work.
4. don't compromise the life and safety of the people working on and near the large piece of expensive equipment.
5. don't compromise your transformer.
6. get a bigger transformer or do a load calculation to prove you don't need one... but nameplate type of info. should say something, to someone.
7. you're correct, not missing something, and not confused.
8. these are just some random thoughts but since they all point in the same direction, I'd be thinking they might mean something....
9. yeah, and what's with those discos anyway?? aye?

 

[jnsane84]

Thanks for all the responses guys. I appreciate your input and help. The 4 Disco's....I have no idea.....it was that way in the Georgia facility. I questioned it but got a bunch of "I dont know"'s. I was totally and completely baffled as to why they had such overkill. Charlie it is indeed a 112.5...my bad. Here at our facility we brought in the 112.5 KVA transformer, subpanel and extra (un-needed in my opinion) disco's. The feed is 480/3 and out to the machine is 208/220. When this machine was purchased I recommended getting the transformer to adequately support the machine minus all of the craziness we ended up with. The senior guy in our department raised so much of a fuss and convinced everyone that we needed this "MESS". I did find out this morning that there has been a change to the original plan and now the welding equipment is going to be fed from a totally different feed now, unlike the original plan to feed it all from that one transformer.