Automated Fixtures Step up transformers for arc movers.

TheTheaterGeek

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In a space with nothing but 110, and like an idiot I assumed the 220 plugged circuit was 220(it isn't). Is a 3000w step up transformer enough for something like a VL3500? Is this even something I should consider?


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In a space with nothing but 110, and like an idiot I assumed the 220 plugged circuit was 220(it isn't). Is a 3000w step up transformer enough for something like a VL3500? Is this even something I should consider?


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You wrote:"I assumed the 220 plugged circuit was 220(it isn't)." But you've yet to mention what it measured. If it measured 208, as in two legs of a 120/208 system, you'd have better options. Please do tell more. Having only 120 volts available, though possible would be quite unusual. I'm suspecting digging a little deeper will reveal the existence of either single phase 120/240 or three phase 120/208 somewhere nearby and, optimistically not too far away. I'd explore looking a little further unless this is a total one-off for you, as in there's no way you'll ever be in this space again, and you're definitely only looking to pull something out of your hat for ONLY this one fixture.
Toodleoo!
Ron Hebbard
 
It is metering at 117. And I know there is three phase in the adjacent room, but no breakout. Just straight into a single smart pack.


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It is coming from the feed to the dimmer room. Into a breaker panel, into smart pack. No breakout or tie in though.


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That combiner is NOT allowed per NEC (the two circuits you would plug into don't have handle ties on the breakers) and if not made correctly, can be lethal. It needs more than just two cables and a receptacle; you need relays to safely isolate one plug from the other to avoid issues with live male pins or shorts when plugged into miswired outlets. There are only two ways to do this correctly - have an electrician install a 208V circuit if the unit will run on 208V, or use a transformer.
 
According to the specs, a VL3500 requires ~10 Amps at 208-240 Volts. We know that a transformer follows the rule: Power In = Power Out / Efficiency Transformers are roughly 95-98% efficient. Because of the lack of accuracy of the spec sheet, we have to figure that the primary of a step up transformer could draw very close to, or more than, 20 Amps. Since most 120 V wall receptacles are on a 20 Amp circuit, it may not work reliably. Inrush current at startup would likely trip the breaker. I wouldn't gamble the cost of a transformer on it.
 
I just tested a 2kva transformer on one. It seems to work fine, thermocoupled the plugs cable and box and everything seems kosher. Breaker is fine. I will ameter the line just to be sure. Is there any risk of damaging the fixture?


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That combiner is NOT allowed per NEC (the two circuits you would plug into don't have handle ties on the breakers) and if not made correctly, can be lethal. It needs more than just two cables and a receptacle; you need relays to safely isolate one plug from the other to avoid issues with live male pins or shorts when plugged into miswired outlets. There are only two ways to do this correctly - have an electrician install a 208V circuit if the unit will run on 208V, or use a transformer.

What would be a round about price for an electrician to do this?
 
The cost will have a lot to do with where you are. In rural areas, non-uniform, no permit, not much other work - maybe $100 or less. In an urban area, prevailing wage/Union, permit and inspection - maybe $500 or more. Find out what electricians have worked on the building and call and ask. A lot better answer than you'll get here.
 
you need relays to safely isolate one plug from the other to avoid issues with live male pins or shorts when plugged into miswired outlets.
The device I cited HAS those relays, and is listed, by NRTL. Not saying it's a panacea, but might be useful in certain situations.
 
What would be a round about price for an electrician to do this?
In addition to what's been posted, consider the following and be an educated consumer:
If there's space in the existing panel to accommodate your new 2 pole breaker, installation will cost less.
If the existing panel requires upgrading to a larger size, or the addition of a sub panel, you'll pay more.
If additional wiring requires the installation of rigid conduit, you'll pay more.
If EMT meets code compliancy, you'll save money.
Here in Canada we still have BX while on your side of the border I believe you have a close to equivalent product referred to as "metal clad" which ought to be even less expensive. Pipe can be cheaper to install over all as you're often installing fewer clamps. If your dealing with poured concrete walls, every hole you drill takes time and costs more money.
If your facility is wired in conduit, and if there's sufficient space within existing conduit to install additional wiring without exceeding conduit fill restrictions AND if the installation of said wiring can be accomplished at at time savings, you could pay less.
If the new receptacle you require can physically be accommodated within the existing receptacle's box, you could realize a savings.
In my experience, labor is always the larger share of the costs. Oftentimes it's better to pay a little extra for materials if they gain a more then they cost savings in installation time.
Non union labor MAY be less costly, although as a retiree with 47 years in the IBEW, I can sense a lightning bolt about to strike me down for having typed that.
Time is ALWAYS money. If you're considering adding a few more similar receptacles in the foreseeable future, you ought to consider having this quoted as an alternative add-on to your original quote as you may find it more affordable to do this in one step or your contractor may elect to install a larger diameter home run conduit to the panel initially to have the extra pipe capacity already in place for your future plans.
If your venue is part of a much larger facility, a college or university for example, they'll likely have electricians on staff who may be able to fit your needs into their regular hours given sufficient lead time.
Bottom line: ALWAYS get at least three quotes, study them meticulously to ensure they're 'apples to apples' competitive. Have them read over by other informed folks if you've any doubts in your abilities to adequately evaluate them. Depending upon who you're dealing with, some forms of barter are possibly negotiable. If a contractor has three kids he or she is hoping to get into a summer theatre program for kids that's operating in your space you may be in a position to negotiate. Possibly the contractor may be trying to purchase tickets to a sold out production in your venue and you may be able to accommodate his or her needs within your booth. You never know. Explore ALL your options.
Please forgive the ramblings of a geezer.
Toodleoo!
Ron Hebbard
 
Whats embarrassing was that using two 120 volt receptacles was SOP when I was in college and we did a children's tour in rural upstate NY. A 6 X 1K auto transformer box with 2 - 500 watt Fresnels each typically - wired however. Looked for a 220 outlet first, two outlets on separate circuits second, and then just took the cover off the nearest panel and >carefully< connected pigtails to what seemed like lightly loaded breakers. Worst case I just attached directly to hot bus bars.

While the neutrals were tied together in the dimmer pack, it was essentially two groups of 3 120 vac devices, so not really the same.

I am unclear how the convert works without, as far as I can see, a 220 receptacle with ground and neutral. I realize that a lot of 220 devices don't need a neutral - just 2 hots and a ground - but obviously my 6 X 1000 did.

(Don't get picky - I knew I couldn't bring all 6 dimmers to full at one time on 2-20 amp circuits - diversity is a wonderful thing.)
 
Whats embarrassing was that using two 120 volt receptacles was SOP when I was in college and we did a children's tour in rural upstate NY. A 6 X 1K auto transformer box with 2 - 500 watt Fresnels each typically - wired however. Looked for a 220 outlet first, two outlets on separate circuits second, and then just took the cover off the nearest panel and >carefully< connected pigtails to what seemed like lightly loaded breakers. Worst case I just attached directly to hot bus bars.

While the neutrals were tied together in the dimmer pack, it was essentially two groups of 3 120 vac devices, so not really the same.

I am unclear how the convert works without, as far as I can see, a 220 receptacle with ground and neutral. I realize that a lot of 220 devices don't need a neutral - just 2 hots and a ground - but obviously my 6 X 1000 did.

(Don't get picky - I knew I couldn't bring all 6 dimmers to full at one time on 2-20 amp circuits - diversity is a wonderful thing.)
They had electricity when you were in college?? DC or AC?
In a moment you're going to admit to using Trico clips and modified Trico fuse extractors to connect tails to live panels.
Just raggin' you Mr. Conner Sir! (One geezer to another.)
Toodleoo!
Ron Hebbard.
 
Have you found the breaker for this receptacle and opened the panel? Did someone substitute a single pole where a double pole breaker was installed? Or did someone take one of the wires off the two breaker and connect it to the neutral buss? You might have a simpler/cheaper solution.

I have to say, I can't quite tell and the facilities guy is hesitant to let a stage electrician go exploring.

As an update I have installed two step up transformers. They seem to be working fine. Keeping a close eye on them though.

Clay
 
I have to say, I can't quite tell and the facilities guy is hesitant to let a stage electrician go exploring.

As an update I have installed two step up transformers. They seem to be working fine. Keeping a close eye on them though.

Clay
I'm in agreement with your "facilities guy", if you're not licensed and comfortable inside a live breaker panel, leave the cover on.
All the best with your transformers and thank you for getting back to us. So many posters rape us for info and never follow up.
Toodleoo!
Ron Hebbard.
 

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