Converting commercial building from Delta to 3-phase

I've been put in charge of gathering some info and of course my research always starts here.

Theater currently has delta-hi leg power. That is kind of pointless for a theater. We rarely need the voltages you can get with delta, but what we really could use is more amperage at 120v and 240v for lighting and sound. I would assume the power company basically just takes the delta leg and puts it on a different transformer, right?

But what I need to find out is how this voltage/phase change will affect things inside the building. There isn't a lot of big stuff except three rooftop HVAC/heat units, one electric dryer (240v currently). Will I have to change things in the main breaker panel? Will I have to do a whole new panel? I have a fair amount of experience with residential 240v, but once you leave the realm of black, red, white, and green, I get hazy. Adding blue is confusing to me, especially with how blue plays with black, red, and white. I mean, I understand the way the electricity works, but I don't know how its physically wired in the building and how it might change things.

You've got an incoming three-phase supply at 277V. High-leg delta is how you get 240 and 120V. There's 240V single-phase if you connect one wire to one phase and another to the second phase. A small (<1/8 of total available power) amount of 120V is available by dividing another phase-to-phase connection at a center tap.

If you're looking for more power out of the system you'll have to learn more about three-phase power and shift some of your 240V or 120V single-phase load to 277V three-phase.

But we don't ever use 208 or 277v for anything in the building.

Right now, I only have two 120v lines trying to supply my entire lighting grid. If I can get another 120v line to it, that's 50% more available amperage. A high leg is useless for getting additional 120v edisons.

The problem is, nothing for theater uses the delta leg, so I'm limited to two lines. Distro boxes, fader racks, audio, everything is all set up for three phase. Right now when I hook up a dimmer rack, I can only use half of the dimmers. If I hook up an Audio distro I can only use 2/3 of the outlets.

You don't use 208 for anything? Odd. We use 208 for some of our moving lights and all of our projectors, because there's no true 240 anywhere in the building. Then again, moving lights don't really care if they get 208 or 240.

Curtis, I've been an entertainment electrician for 30+ years and I've never run into this. But if I did, this is what I'd do...

I'd find a Commercial Electrical Contractor and tell them I wanted a walk-through and a bid. I don't generally like to take advantage of people, but those services are free and you may actually wind up engaging their paid services. OTOH, you may find out it is prohibitively expensive. But I'll bet you learn a thing or two along the way.

I am surprised you do not use delta for anything. Right below me (I am in the catwalks right now) I have 5 400 amp panels that use exactly what you say you don't.

I'm gonna be "That Guy" for a minute...

This is REALLY a job for a commercial electrician.

You are dealing with Assembly Space. One of the highest risk classifications in the code (because of its potential impact on large numbers of people, life safety, etc).

EVERYONE can make a mistake. That's why electricians have insurance.

If there was ever a mishap in work done without a license or permit, someone (Board if Directors ?) could be held personally liable.

Please hire an electrician for this one.

I do agree with SVreX here. get a professional on it. THat kind of power is nothing to play with.

What I would do, is have some camlock connectors put in and use modular step down boxes and strips from Lex or something

EvanR wrote: You don't use 208 for anything? Odd. We use 208 for some of our moving lights and all of our projectors, because there's no true 240 anywhere in the building. Then again, moving lights don't really care if they get 208 or 240.

I could run darn near any voltage into the lights we rent, but no one around here rents LED fixtures set up for 208 or 240. So it makes no sense to wire a grid with all possible voltages just so I can change to twist-locks on all the fixtures and swap out fuses in each unit. They all come wired and fused for 120v, so I use 120v.

I'll elaborate. My "grid" is a conglomeration of trusses and 1-1/2" sched 40 hanging from the ceiling. There is a 200A/240v panel which has 20 breakers in it. Now... try to follow this BS that I inherited from the previous guy. From each breaker, there was a mass of THHN that went to a table that had 18 residential sliding dimmer switches in it. Then another mass of THHN went back to the panel to some bus bars connected to SJOOW (a bunch of orange extension cords) up to the grid. I took one look at it and disconnected the whole panel, threw the table away, and installed cam locks instead for distros. Any LEDs that I put up there get powered by extension cords from the four corners.

So, the plan is to repower that subpanel and run proper conductors up to the grid, terminated with edisons so that each pipe or truss has two circuits - each circuit with three duplex outlets so that no more than 6 instruments can be put on one circuit. That takes care of any power needs for LEDs. My problem is, if I need to run old-school lamps, I only have 200A to play with. If I had a third 120v leg that I could pull to the grid, then I would have two dedicated 120v legs to power some 4-pack dimmers in the grid.

My main problem is, if I want decent lights in this space, I either HAVE to rent LEDs, or rent a dimmer rack. If I rent a dimmer rack and put 18 lamps up there, I'm at the edge of my load capacity and can't switch on the amps for sound.

As it is, I am renting, hanging, and circuiting every show individually. I don't want to ADD to my work by converting instruments to 208 or 277 every time I do a show, then converting them back.

This is a relatively small black box (50 x 60), and like I said I'm not the best with this, but it doesn't seem to make sense to add labor for a small increase in current when I could not add labor and get 50% more current.

SVreX wrote: I'm gonna be "That Guy" for a minute... This is REALLY a job for a commercial electrician.

No problem being "that guy"

This WILL be a job for a commercial electrician. As I said, I'm just starting the research and I thought I would pick your brains first.

In reply to curtis73:

I was hoping you'd say that.

Carry on.