MEP Coordination problem

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Designer69

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Hi I have run into a problem that will probably cost me some money from my salary so I was wondering if anyone here might have quick-fix solution I hadn't thought of..

5 terminal units w/ box fans and electric heating coils were supplied at 208/3ph but due to a coordination problem I had wired them on the dwgs to 480V/3ph panels.

there is not enough capacity to re-wire them to 120/208v panels since the dry-type xfmr for those would be undersized to handle the combined load of roughly 50KW.

although the fans alone can be rewired to 120/208 panels since they are minimal loads (1/3hp each), however the elec. htrs are the prob. they amount to most of the load which again is around 50kw.

the best quick fix solution we have so far is to disable the elec. htrs on the TU's, wire the fans to 208 panel and order new duct mtd elec. heaters rated at 480V and install them down stream.

I spoke to a rep from Titus and he said they would probably work at 277V.

any way to get 277V/3Ph from a 277/480V/3ph panelboard?

appreciate it.
 
If you power a 208 volt heater with 277 volts, it will be putting out 177% of its rated heat. I doubt that it would survive long, no matter what the rep said. Also, you cannot get 277/3 from a 480/3, without using a step-down transformer. But if you are going to do that, you might as well step it all the way down to 208/3.

My suggestion, and I admit it?s not all that helpful, is to install either one transformer (if the five units are close to each other), or five smaller transformers (if the units are far from each other), to give you the 208 volts you need.

Another possible solution is to replace the existing transformer with a larger one. That may be a problem, however, if you run into sizing issues with the conduits housing the primary and secondary conductors, or with the panel that the transformer serves.

p.s. If you are the "designer," then was there a PE involved in the project? If so, it should be the PE who takes the heat for lack of MEP coordination, not the designer.
 
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