malachi constant
Senior Member
- Location
- Minneapolis
We are engineers redesigning a distribution system to a large school facility. Long story short there is an existing 208V service that steps up to 600V in order to distribute around the building. We had assumed this was 480V but fortunately caught it a couple months before we finalize the design. Questions:
1. I would love to reuse the 600V feeders to distribute from a new 480V board. The feeders are sized in such a way I am not concerned about load size or voltage drop. Conduit reuse would likely not be an issue. However the feeders are aluminum, and at least 40 years old. I assume I should be recommending conductor replacement to the Owner? There are a lot of cons to reusing, with the only pro I can think of being "you save money".
2. I would love to retap the step-down transformers to 480V:208V. But looking at nameplate, taps bottom out at 540V. So I assume reuse of these on a 480V system is not an option - am I correct?
3. I've been doing this 20 years and had never heard of a 600V system installed in the US. I assume this is not unheard of, but I'm correct that it's pretty weird, right?
We have the option to keep it, but it would mean that all our ~new~ distribution and mechanical equipment would have to be 208V, which would add quite a bit of cost to the project. Also we are adding a generator and creating an emergency distribution system - that was planned to be at 480V. Most all lighting is being replaced, so we were assuming new 277V lighting throughout. Wouldn't be the worst thing to keep lighting systems at 120V (could reuse all their home runs & branch circuitry) but would make all new em lighting be stepped down to 120V.
If anyone has answers to the conductors and transformers question, or general thoughts on 600V distrubution, I'd appreciate hearing them. Thanks!
1. I would love to reuse the 600V feeders to distribute from a new 480V board. The feeders are sized in such a way I am not concerned about load size or voltage drop. Conduit reuse would likely not be an issue. However the feeders are aluminum, and at least 40 years old. I assume I should be recommending conductor replacement to the Owner? There are a lot of cons to reusing, with the only pro I can think of being "you save money".
2. I would love to retap the step-down transformers to 480V:208V. But looking at nameplate, taps bottom out at 540V. So I assume reuse of these on a 480V system is not an option - am I correct?
3. I've been doing this 20 years and had never heard of a 600V system installed in the US. I assume this is not unheard of, but I'm correct that it's pretty weird, right?
We have the option to keep it, but it would mean that all our ~new~ distribution and mechanical equipment would have to be 208V, which would add quite a bit of cost to the project. Also we are adding a generator and creating an emergency distribution system - that was planned to be at 480V. Most all lighting is being replaced, so we were assuming new 277V lighting throughout. Wouldn't be the worst thing to keep lighting systems at 120V (could reuse all their home runs & branch circuitry) but would make all new em lighting be stepped down to 120V.
If anyone has answers to the conductors and transformers question, or general thoughts on 600V distrubution, I'd appreciate hearing them. Thanks!