add a phase

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mshields

mshields

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Location
Boston, MA
I have a application for a restaurant out in the boon docks. They need 208V, 3 phase power but only single phase power is available. I've been asked to evaluate the cost differential between getting the utility to bring in the three phase power OR using an add-a-phase device.

I have no experience with these. Can anyone tell me who makes them? Can anyone comment on the pro's and con's of using one. This would be for maybe a 400A service.

Thanks
 
What is the 3 phase load(s)? If you need 400A of 3 phase, I think the only thing that would work is a rotary phase convertor, which would be pretty expensive, along with the need for ongoing service, and lots of standby losses due to it running constantly.

If it's just one 3 phase load, like a garbage disposal or other motor, either use an add-a-phase just on that, or what about using a VFD w/ a single phase input. This would give you soft start, overloads, etc. See: http://www.mikeholt.com/code_forum/showthread.php?t=81283

Mike
 
Before you start remember if you really want 400A 3 phase service you'd actually need 1200A single phase to make it. The PoCo is likely to give you 3 phase service cheaper at 240V or 480V... It'll probably cost extra for 208V.

Why do they need 3 phase? If its just one or 2 items you might be better of changing a motor or 2. If you get 240V most restaurant equipment is single phase and or won't allow connections over 120V to ground especially dishwashers with electric heating elements so the 3rd phase is hardly used.
 
Voltages of the future!

Voltages of the future!

DaveTap said:
The PoCo is likely to give you 3 phase service cheaper at 240V or 480V... It'll probably cost extra for 208V.
Click to expand...


I don't charge any more for 208Y/120 service than I do for 240/120 delta, or 480Y/277. In fact, I encourage customers to use 208Y/120, or 480/277 over a 240/120 service, because my superiors believe 208/120 and 480/277 are the voltages of the future for 3 phase. And therefore, that is what I believe. :)
 
wirenut1980 said:
I don't charge any more for 208Y/120 service than I do for 240/120 delta, or 480Y/277. In fact, I encourage customers to use 208Y/120, or 480/277 over a 240/120 service, because my superiors believe 208/120 and 480/277 are the voltages of the future for 3 phase. And therefore, that is what I believe. :)
Click to expand...

how do you pull that off, being as 480V stuff is so much more expensive?
 
petersonra said:
how do you pull that off, being as 480V stuff is so much more expensive?
Click to expand...

For pad mounted transformers it depends on the kVA (at least for this utility company). For the smaller transformers 150 kVA and smaller, the 480/277 ones are more expensive, but for larger than that, the prices are very comparable and for a 500 kVA, the 208/120 is actually more expensive than the 480/277.

For this application, you are probably correct.
 
wirenut1980 said:
For pad mounted transformers it depends on the kVA (at least for this utility company). For the smaller transformers 150 kVA and smaller, the 480/277 ones are more expensive, but for larger than that, the prices are very comparable and for a 500 kVA, the 208/120 is actually more expensive than the 480/277.

For this application, you are probably correct.
Click to expand...

I was thinking more about the panelboards.
 
Dave,
remember if you really want 400A 3 phase service you'd actually need 1200A single phase to make it.
Click to expand...
Are you sure? I think that it would 692 divided by the percentage efficiency of the converter.
Don
 
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