Design 3 Phase for Sound Stage

[Design Time]

Hello All,

We are building a new sound stage and post facility in upstate NY and need to decide if it is worth the money to upgrade to 3 phase power. This is a gut renovation and the existing power is 200 amp single phase which we know is not sufficient. We can get 400 amp single phase or roughly 96,000 watts of available power at no additional cost or pay about 10k for 600 amp 3 phase which per my electrician yields more like 72,000 watts of power. We look at that 10k and think perhaps we should use the money for a back up generator instead.

The building is about 9,000 sf feet total which includes a set shop, grip storage, 2,000 sf shooting stage with 3 sided cyc, screening room, editing suites and room to sleep up to 12 crew members for extended periods. With the increasing use of LED light sources and less need for heavy draw lighting; we think the single phase should suffice.
That said, we wouldn't want to lose potential clients who aren't comfortable without the availability of 3 phase.

We are torn between these two options and almost every opinion I get is either adamantly for or adamantly against the necessity of 3 phase. Would love to hear any comments!

Thanks!

 

[BobHealey]

Assuming all the legs are being used as 120V legs, 400A singlephase yields (2 legs x 120V leg to neutral * 400 amps) = 96,000 watts. 600A three phase yields (3 legs * 120V leg to neutral * 600 amps) = 216,000 watts. Not sure how you derived the 72KW total for 3 phase, but double check the numbers. You're going to have enough high current 208/240V devices, I'd go for the 3 phase. Your set shop will thank you when they add in large saws, welders, big compressors, etc. Note that my wattage numbers do not account for any required derating.

 

[robartsd]

600 amp 3 phase which per my electrician yields more like 72,000 watts of power.

72,000 watts sounds more like 200 amp 3 phase (3 phases x 200 amps x 120 volts).

 

[Design Time]

Assuming all the legs are being used as 120V legs, 400A singlephase yields (2 legs x 120V leg to neutral * 400 amps) = 96,000 watts. 600A three phase yields (3 legs * 120V leg to neutral * 600 amps) = 216,000 watts. Not sure how you derived the 72KW total for 3 phase, but double check the numbers. You're going to have enough high current 208/240V devices, I'd go for the 3 phase. Your set shop will thank you when they add in large saws, welders, big compressors, etc. Note that my wattage numbers do not account for any required derating.

Assuming all the legs are being used as 120V legs, 400A singlephase yields (2 legs x 120V leg to neutral * 400 amps) = 96,000 watts. 600A three phase yields (3 legs * 120V leg to neutral * 600 amps) = 216,000 watts. Not sure how you derived the 72KW total for 3 phase, but double check the numbers. You're going to have enough high current 208/240V devices, I'd go for the 3 phase. Your set shop will thank you when they add in large saws, welders, big compressors, etc. Note that my wattage numbers do not account for any required derating.

Thanks Bob. It was actually 3 phase 200 amp that was being proposed, not 600 amp. My mistake.

 

[Design Time]

Assuming all the legs are being used as 120V legs, 400A singlephase yields (2 legs x 120V leg to neutral * 400 amps) = 96,000 watts. 600A three phase yields (3 legs * 120V leg to neutral * 600 amps) = 216,000 watts. Not sure how you derived the 72KW total for 3 phase, but double check the numbers. You're going to have enough high current 208/240V devices, I'd go for the 3 phase. Your set shop will thank you when they add in large saws, welders, big compressors, etc. Note that my wattage numbers do not account for any required derating.

72,000 watts sounds more like 200 amp 3 phase (3 phases x 200 amps x 120 volts).

Yes. Thanks. Any other thoughts on reliability of delivery; overall efficiency, usage rates or advantages of 3 phase vs. single? Besides saw, welder and AC units (four 5 ton units) I don't expect a lot of other high current 208 /240 devices. Also, for 3 phase; the 120/208 wye system seems to be the correct choice versus 120/240 delta which is also available; correct?

 

[BillConnerFASTC]

Decisions like this are about balance and needs. Should you give up some toilets or a quiet enough space for this - no. My guess if $10k is a big decision on his project, try to get along without it. For a 3 phase table saw, you can get a small converter for much less. Fans - HVAC - is usually the kicker. Single phase is available but when does higher maintenance cost catch up?

 

[robartsd]

Also, for 3 phase; the 120/208 wye system seems to be the correct choice versus 120/240 delta which is also available; correct?

Yes, you would want wye not delta. With delta, you'd only get 2 120V legs--the third leg is 208 from neutral. Delta is used in industrial settings where most of the load requires the higher voltage but limited 120V service is also needed.

 

[Footer]

The only other issue is how shops set up gear. Most gear rolling into a space from a rental shop will be configured for 3 phase operation. Anything you pull from the major shops will be like this. Do you have any need for truss and motor rigging or automation? I know you might not need it now, but down the line it might come up.

I would say rip the band aid off now and get it put in. I would much rather have this then a back up generator. You don't want to be that place that loses bids because every piece of gear needs to be reconfigured before you hit the dock.

 

[porkchop]

If I where renting your space and I would expect to tie into 3 phase Wye power. If fact, if you told me you had a 400A single phase tie-in available I'd probably assume I was talking to a front office person that didn't know what they where talking about and prep for 3 phase anyway. Single phase may be more prevalent in the NY film world than it is anywhere I've worked, but that's what I'd expect. This of course is a completely irrelevant discussion if you have the distribution gear on hand so I can just plug in whatever I like and it "just works" (say for the sake of argument an array of 110v and 220v 20A single phase outlets and a 50A outlet or two for those huge lights that film guys seem to love).

 

[FMEng]

For decisions of that magnitude, you should have counsel from a design team. You need to speak with your mechanical engineer, your electrical engineer, and possible your acoustician, and let them make this decision. What will drive this are the HVAC systems. For big spaces like that, where you need very quiet heating and cooling (high volume, low velocity), it may be more practical to use three-phase power, and it might be cheaper over the long haul. Three phase motors are more efficient, run more smoothly and quietly, and tend to be more reliable.

 

[teqniqal]

building a new sound stage and post facility . . . which includes a set shop, grip storage, shooting stage, screening room, editing suites and room to sleep.

Different parts of this facility need different types of power. It is typical that your HVAC, shop tools, and motorized hoists will need 3-phase for the motors, but as a SOUND [and video] stage with technical equipment and a real concern for a quiet electrical system, single phase power is the quieter electrical solution (see: http://www.middleatlantic.com/~/media/MiddleAtlantic/Documents/WhitePapers/PowerPaper.ashx). There is no reason that you can't have both. Just keep them labelled clearly and make sure you use NEMA standard receptacles for everything so someone doesn't plug into the wrong power source.

Your existing single-phase power is derived from two of the three legs of a 208/120V (or higher) 3-phase service coming into the building via a transformer that steps it to a 240/120V single-phase. Adding a 3- phase service to power your HVAC, shop tools, and motorized hoists would only require a new transformer and service disconnects for that portion of your electrical system. Shifting the present HVAC, shop tools, and motorized hoists loads to the new 3-phase system would 'free-up' available power for your LED lighting and technical equipment (albeit you may need new motors - you didn't say how much existing stuff was to remain in the remodel). Having two transformers between the HVAC, shop tools, and motorized hoists will provide a lot of noise filtering for your technical equipment, and any noise generated by the non-linear power supplies in all of the electronics on the technical side will be largely self-cancelling due to the single-phase power configuration.