This is topic Booth Electrical Loads in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.


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Posted by Barry Floyd (Member # 385) on 01-03-2003, 11:38 AM:
 
I've got to submit to our electrical engineer who is designing the "Power layout" for our drive-in, a table of "electrical loads" for our building, and had a question about the booth load requirements.

I've got plenty of power available from the street, as 3 phase power is already run to the site at the edge of the road.

My current lamphouse in storage is an 4kw ORC, but have considered replacing it with either a Strong or a Xenex II. I noticed when I removed my ORC from it's former booth that it had both 3 phase running to the power supply, and a 120v circuit run to the lamphouse controls... or something like that. I've got to tell my electrical engineer what size circuits to install and I don't have a clue.

My projector is a Simplex XL with a RCA 9030 soundhead. I was figuring a 30amp 120v dedicated circuit would handle the projector, and another 20amp 120v dedicated circuit to cover the platter and MUT.

Our theatre will end up being a twin screen by the beginning of 2004, but will open in May of 2003 with one screen. I'm having the engineer size the service entrance and panel board to accomodate both screens for ease of expansion in the future, but I need to tell him what to put in there now.

Any help would be appreciated....
 
Posted by Adam Martin (Member # 641) on 01-03-2003, 12:22 PM:
 
I can't help you with your power ratings, but I can warn you that there are two kinds of three-phase power. There's three-phase where all three phases are stable voltage and there's three-phase where two are stable and the third is wild. One of these is called Delta, but I can't remember which.

If you're going to use that third phase, make sure that the power company has the line transformered accordingly or you're sure to blow up a few things when the line fluctuates from 100v to 200v! Talk about eleventh hour excitement.
 
Posted by John Pytlak (Member # 331) on 01-03-2003, 12:24 PM:
 
Provide your electrical engineer the electrical specifications of each piece of equipment you intend to have operating. Most should be in the "Manuals" section of Film-Tech. Good design will factor in additional load and additional circuits for later additions, as it's easier than ripping things out later to upgrade for unexpected additional circuits or load. Don't forget to have separate conditioned circuits for digital equipment (automation, sound system, computer). Emergency lighting and announcement capability is a good idea, even if not mandated by code in your area. And don't forget lightning protection. [Eek!]
 
Posted by Jon Bartow (Member # 241) on 01-03-2003, 12:56 PM:
 
Three phase delta is the kind you want. (all three legs are usable by single phase devices, as all three legs are stable) Not many places still have three phase wye but they are out there. If you have a three phase wye setup then you will find that every third slot for a breaker in your panel will be useless except for three phase devices.
Is your projector motor three phase? or 220v? or 110v? It makes a big difference in the amp load required.
Are you running a 70v amp for field speakers? if so big amps can be very power hungry.
Try very hard (beg and plead if you have to) to have all of your sound equipment on the same phase and don't let them put any dimmers or big motors on that phase either (projector motor, HVAC, ice machine compressors, etc). It will save many potectial problems down the road. Also you want an isolated ground for the booth, not grounded through the conduit downstairs through the concession stand, but a good ground from the panel in the booth.
20 amps is usaully enough for a 110v or 220v projector, they are usually only 1/4-1/2hp motors.
Make sure your electrician uses a breaker panel that is big enough to have several more circuits installed (if you are adding a screen later, than you will probably add another breaker panel, it simplifies things a bit. make sure your electricians plan for that too.
Also, depending on the type of breaker panel, it can sometimes be a bit of a challenge to get replacement breakers. It would be a good idea to have a spare of each type/size used. They can even put the spare breakers in an unused slot in the panel.
John is very wise to caution you about lightening protection. field speakers on poles are excellent lightening rods as is a building alone in the middle of a field. Make sure the field speaker lines are well protected.
As has been said, provide your elec. eng. with all of the equipment specs and s/he will be able to plan accordingly. My guess is that a 500-600amp three-phase (delta) will more than suffice for your current (pun very intended [Roll Eyes] ) and future needs.
Jonathan
 
Posted by Ian Price (Member # 14) on 01-03-2003, 01:05 PM:
 
I don’t know about a Drive-In but this is what I understand that each auditorium needs in an indoor multiplex.

Ask for Switchable Circuit Breakers as you may be turning these off each night.

3 Phase 30amp circuit for the Lamphouse
120v 20amp Exhaust Fan
120v 20amp Projector
120v 20amp Automation
120v 20amp Platter
120v 20amp Make-Up Area (Only one needed per complex)
120v 20amp Accessory Plugs in Booth
120v 20amp Sound Processor
120v 20amp for each 2 Amplifiers
120v 20amp for each House Dimmer
120v 20amp Isle Lights
120v 20amp Auditorium Plugs for vacuums, blowers and such (Leave on 24 Hours)
120v 20amp Emergency Lights & Exit Signs (Leave on 24 Hours)
120v 20amp Clean-Up Lights (Leave in 24 Hours)

The load on each circuit will be low, but this is a great way to isolate each circuit for service and diagnosis. This can probably be served with a 200amp panel.
 
Posted by Barry Floyd (Member # 385) on 01-03-2003, 03:48 PM:
 
Ian, you never cease to amaze me the long lists of categories you can come up with, and all very accurate. On a side note to this topic, I took the list of "operating expenses" you listed in the "Business Plan" topic a year or so ago, and incorporated them into our cash flow plan for the drive-in. I had my loan approved for the purchase and construction of the drive-in in less than a week. My banker said, "For someone who's never been in this business before, you sure have your expense categories very well detailed."

John and Jon had mentioned "lightning protection" for the booth, I'm assuming for stray random strikes in the field running in on the field speakers. We will not have any field speakers... now days they're just too costly to maintain, and also expensive to install.
I've got an FM stereo transmitter that runs at a 1/2 watt that won't broadcast the signal much further than the property boundaries.
 
Posted by John Pytlak (Member # 331) on 01-03-2003, 04:00 PM:
 
Your projection room / concession area sitting in the middle of an open field is a nice target for lightning. Protect those buildings, and also protect against the damage a lighting hit will have if it gets into your power lines (e.g., if you have field lights at the top of your screen, they are likely to get hit, with the surge knocking out some of your equipment).

My home has lightning rods, and a surge protector where the power line enters the house. My phone, cable, and antenna lines all have "lightning arresters", with a solid path to an outside ground. Four houses in our hilltop neighborhood have been hit, with varying levels of damage.

I've lived through enough lightning storms sitting in a drive-in booth to appreciate the need for lightning protection. [Eek!]
 
Posted by Adam Martin (Member # 641) on 01-03-2003, 04:08 PM:
 
I can't remember the last indoor theater project I've been involved with that didn't have lightning rods around the perimeter of the roofline and on each RTU and exhaust fan.
 
Posted by Jack Ondracek (Member # 1466) on 01-03-2003, 04:11 PM:
 
Barry, you might up that figure for the lamphouse(s) a bit. Our older X-60 supplies were rated for 50 amp circuits. You could probably downgrade that a bit if you put in switchers... but the extra capacity won't hurt.
 
Posted by Mike Fitzgerald (Member # 1304) on 01-03-2003, 04:12 PM:
 
Thanks for the information. I was looking for the very same information for my portable booth. The only difference is that I am going to be using a 3 phase generator with carbon arcs lamps. I think the lamphouse alone will use 50 amps 3 phase just by themselves and about another 8=20 amp circuits for the rest of the booth.
[thumbsup]
 
Posted by Paul G. Thompson (Member # 655) on 01-03-2003, 05:03 PM:
 
Supply your engineer with electrical demands of each and every component you intend to use.

And be advised....if any of this equipment does not have a UL certification, the electrical inspector will probably not sign it off and allow operation.

If any of your equipment does not have the UL sticker physically affixed to the equipment, be prepared to spend alot of time finding out the UL info the contractor/inspector wants.
 
Posted by Bruce Hansen (Member # 281) on 01-03-2003, 05:11 PM:
 
OK, it's been a long time since I studied this stuff, but isn't 220 Delta the system that does not have a common neutral, and therefore is only good for 3 phase 220 devices? And I believe that one leg is a little higher than the others, but does not vary. "Y" has a common neutral (the center point of the "Y"), and can be used for 115 volt devices.
 
Posted by Ron Lacheur (Member # 1126) on 01-03-2003, 05:21 PM:
 
from:
http://www.franceformer.com/foreign_current/home.htm

Delta systems: In its basic form the delta system utilizes a 3-wire scheme -- 3 line (or "hot") wires. One phase (that is, line-to-line) may be center-tapped, with the centertap becoming a neutral conductor. On such center-tapped systems the higher voltage is derived from a line-to-line connection while the lower voltage is derived from a line-to-neutral connection. So, the indicated higher voltage in the tables may be either 3-phase or single phase; however, the indicated lower voltage is always single phase. Delta systems may be recognized in the tables by the ratio of the line-to-line to line-to-derived-neutral voltage, i.e.the higher voltage is twice the lower voltage.
 
Posted by Gordon Bachlund (Member # 124) on 01-03-2003, 05:40 PM:
 
Today the most common three-phase electrical services are “wye” connected, usually 120/208V and 277/480V in the US. Thus, electrical panels will have three “hot” buses (phases A, B and C) and a neutral bus, plus a separate ground bus. Any phase to neutral connection will afford the lower voltage (120V or 277V), while any phase to phase connection will afford the higher voltage (208V or 480V single phase), and while any connection to all three phases will afford actual three-phase power (208V or 480V 3-phase).

Some utilities still employ an older scheme that was derived from a delta connection of three single-phase transformers, one larger than the other two, to afford both 120/240V single phase (from the larger transformer which has a center tap for the neutral), or 240V three-phase from all three. This enabled a single bank of pole-mounted transformers to serve a building’s lighting load at 120/240V through one meter, and a building’s three-phase “power” load through another meter. Usually the rate was a bit lower for the “power” load. I have seen this in countless neighborhood theatres in the Los Angeles area in the 50s and 60s. One house in which I worked was served 125VDC by the local utility, and the DC service was used for the projection lamps. When I asked why the utility was still selling DC, I was told that some older downtown office buildings had DC services for their elevators, obviously pre-dating the more modern Ward-Leonard style motor-generator drives.

Barry, those who have advised that you provide the electrical engineer with a complete list of known (and future) loads are correct. He will especially appreciate seeing copies of specifications and manuals. He will then perform such calculations as will ensure that your installation is proper and safe, to say nothing of meeting code. And, yes, most inspectors will look for UL labels, dedicated “green” grounding conductors, transient voltage surge suppressors, proper lightning protection where required, and other safety related practices.
 
Posted by Steve Guttag (Member # 268) on 01-03-2003, 08:57 PM:
 
Be wary of supplying a list like the Ian mentioned...whilst you will want "circuits" like that...that isn't your load persay. The actual draw on a typical single-projector multiplex type load panel is typically from 40-50amps 3-phase. That is...with your show running and if you were to measure the feeder lines with a ammeter that is about all you would be using.

Obviously, your lamp size, number of amplifiers and various lighting circuits can affect this.

A circuit breaker that is 20 amps protects the wire connected to it. Just because you have some 30 20-amp circuits in the panel doesn't mean you need a 200-amp panel and service.

Your Electrical Engineer (with his/her PE) will want to know what your actual load will be and how many branch circuits (you don't want to get a small panel and then run short of circuits).

You then will want to provide your best estimate of the actual load on each circuit (projector motor, dimmers...etc)...that way they can balance out the panel so that each leg will have a similar load. A motor may draw 20 amps or so to turn on but run on less than 5-amps. So for most of the time, 5-amps is the load on that circuit (phase) but you will want a 20-amp circuit to handle the turn on surge.

If you spec willy-nilly all these 20-amp circuits (as if they are all 20-amps all the time) you will be paying for that much service whether you use it or not in some areas. If it is a renovation you may have to pay for a "heavy-up) if it is new, you may be given 277/480 lines and will have to pay for the step-down transformers...the larger the KVA (kilovolt-amps) the more you pay.

Steve
 
Posted by Paul G. Thompson (Member # 655) on 01-03-2003, 09:13 PM:
 
I doubt that you will find any closed delta power being used in new construction these days. It is all open delta as some have pointed out.

I think you will also find the reason for the electrical contractor's request is to make sure the load is balanced, and that you have adequate ampacity in the facility's wiring.
 
Posted by John Walsh (Member # 168) on 01-03-2003, 10:52 PM:
 
At our recently-opened theater in Minneapolis, we specified all audio equipment be on the same phase, and lighting be on the same phase. This was documented in the drawings, and the architect just made every breaker panel the same for every auditorium.

The electrical inspector noted this, and insisted we "break up" the load arrangement because (he said, giving an example) if all the lights are on the same phase at all panels, the phases may be unbalanced.

So, we had to change which phase things went on at each auditorium. Luckly, this theater had 15 auditoriums, so five panels had one arrangment, (lights on phase A for example) the next five a different arrangement (phase B) and the last five on phase C.

I wanted to simply switch around the three power leads inside the breaker box, so the breakers would be in the same location for every auditorium, but on differnt phases. (I really like making all equipment the same since it's easier to train people.) The electrical inspector could not think of anything in the code that would'nt allow this, but "just didn't like the idea" so would not allow it.

Since we use projectors with freq converters, the issue of phase matching for interlocking projector motors wasn't a concern.

Does anyone think this is a bad idea?
 
Posted by Gordon McLeod (Member # 33) on 01-03-2003, 11:03 PM:
 
In a building in canada all panels are supposed to have the phases in the panel the same
I usually buld the audio racks for a 60amp single phase feeder with a breaker on each outlet down the strip inside the rack this ensures the rack is treated as a single device (they also get approved in my shop as such)
 
Posted by Paul G. Thompson (Member # 655) on 01-03-2003, 11:06 PM:
 
The only thing I can see that would be an issue is phase rotation. But, since there are no phase sensitive equipment present, who cares?

However, if you have a 3 phase motor or a HVAC 3 phase system, I can see why the electrical inspector would not allow it.

It could be he didn't allow it because of the "standardization issue".
 
Posted by Jack Ondracek (Member # 1466) on 01-04-2003, 11:46 AM:
 
quote:
from Paul T:
And be advised....if any of this equipment does not have a UL certification... be prepared to spend alot of time finding out the UL info the contractor/inspector wants.
You still whining about that relay, Paul? [Big Grin]
 
Posted by Paul G. Thompson (Member # 655) on 01-04-2003, 02:28 PM:
 
Jack, you darn tootin! [Big Grin]

But actually, I thought that would be a good thing to post, as there are many others who fall into that trap. [Smile]
 
Posted by Bruce Hansen (Member # 281) on 01-04-2003, 06:57 PM:
 
The three phases should be balanced, that is, have the same amount of current draw. If the phases are not balanced you will have a high neutral current. This will result in a voltage on the neutral, and this is one of the causes of hum in audio, and video. I recently received a phone call from a friend who had just had a video facilty wired all on the same phase, because that is how he was told to advoid hum. He had terrible hum problems. I told him to forget what he had been told, and rewire things to balance the phases. The hum went away.
 
Posted by Gordon McLeod (Member # 33) on 01-04-2003, 07:12 PM:
 
In a properly grounded sound system the influence of neutral current is a non issue. Also proper sizing of the neutral conductor is criticle
Several new studios actualy use a balanced neutral where neutral is actually 60v out of phase with the hot legs
 
Posted by Adam Fraser (Member # 1074) on 01-04-2003, 10:34 PM:
 
We have the 480v 3 phase and there are three or so transformers outside the building for us. And to put things into perspective we have a 12 ft by 12 ft room in the basement completely dedicated to power boxes and knife switches. Altough this might be overkill for a 1 screen, it sure makes it easy to troubleshoot when we have power problems. I second the lightning rods though, we got hit by lightning a couple years back and it somehow knocked out our 3 phase power, left our single phase alone, and finally grounded out through our well pump.
 
Posted by Bruce Hansen (Member # 281) on 01-05-2003, 05:50 PM:
 
With all due respect, Gordon, you may have something confused. If a conductor has 60 volts on it, it is not a neutral; the three phases are out of phase with each other, so how would you phase the neutral you are talking about? I can't see how that would ever work, and it would NEVER NEVER NEVER pass electrical code here in the states. What you may be thinking about is: sending the three phases to a group of outlets, but only one neutral, and connecting all the neutrals on the outlets to this one neutral. If the current flows of the three phases are balanced (the same) there will not be any neutral currnet traveling back to the bracker box, and no voltage drop across the neutral run back back to the bracker box. This concept has been used here for a long time to keep hum down, especialy for long power runs.
 
Posted by Gordon McLeod (Member # 33) on 01-05-2003, 06:36 PM:
 
Sorry but that is what I ment it is gaing popularity in some US westcoast studios and has gained alot of popularity up here in broadcast studios
 
Posted by Steve Guttag (Member # 268) on 01-05-2003, 09:21 PM:
 
What it is termed here in the states is "Balanced Power" There are special restrictions on its use and installation with proper notifications.

All legs are "hot" and its chief purpose is noise immunity.

You'd be surprised what will fly here in the states. I don't recall any of the conductors being termed "Neutral" though. Neutral carries a specific meaning and MUST always be coded White for 120VAC service or Grey in 277 (in the US).

Steve
 
Posted by Richard Fowler (Member # 893) on 01-05-2003, 09:58 PM:
 
Hmmm......grounding to the rebar on the roof of a building in Mexico....running to ground and neutral buss bars in different locations of a booth in Peru.....Exposed ballast resistors glowing on a wall in Brazil....40 HZ and below power in India....we need more pilots [Frown]
 
Posted by Jeffry L. Johnson (Member # 453) on 01-06-2003, 02:04 PM:
 
Balanced Power
Equi=Tech
Equi=Tech Balanced Power FAQ

How does balanced power help to solve ground loop humming
here
The Origin of Balanced Power
here
 
Posted by John Hawkinson (Member # 1135) on 01-07-2003, 01:17 PM:
 
Huh. This is all interesting and fascinatingly disturbing stuff.
Jeff's last link asserts this is referenced in Article 530(G) of the 1996 NEC. In case anyone was wondering, I decided to go dig around in the NEC to see what it says.

It turns out that it's not in 530 anymore in the 2002 NEC, but there are some references elsewhere. (Article 530 is "Motion Picture and Television Studios and Similar Locations").

Instead, balanced power seems to be the subject of Article 647, "Sensitive Electronic Equipment." They seem to refer to it both as "sensitive electronic equipment" as well as "Technical Equipment," though the term "technical equipment" seems to be used elsewhere within the NEC(*).

I suppose the only terribly interesting comments in the NEC are in Section 647.7 Receptacles, (A) General:
code:
(1) All 15- and 20-ampere receptacles shall be GFCI pro-
tected.
(2) All outlet strips, adapters, receptacle covers, and face-
plates shall be marked with the following words or
equivalent:
       WARNING--TECNICAL POWER
  Do not connect to lighting equipment.
    For electronic equipment use only.
        60/120 V. 1{phi}ac
          GFCI protected
(3) A 125-volt, single-phase, 15- or 20-ampere-reated recep-
tacle outlet having one of its current-carrying poles
 connected to a grounded circuit conductor shall be lo-
cated within 1.8m (6 ft) of all permanently installed
 15- or 20-ampere-rated 60/120-volt technical power-
system receptacles.
(4) All 125-volt receptacles used for 60/120-volt technical
power shall have a unique configuration and be identi-
fied for use with this class of system. All 125-volt,
 single-phase, 15- aor 20-ampere-rated receptacle outlets
and attachment plugs that are identified for use with
grounded circuit conductors shall be permitted in ma-
chine rooms, control rooms, equipment rooms, equip-
ment racks, and other similar locations that are re-
stricted to use by qualified personnel
(*) For what it's worth, the only way I see to get to Article 647 from Article 530 is a reference in 530.11 "Permanent Wiring" permitting "communication circuits; audio signal processing, amplicfications, and reproduction circuits; Class 1, Class 2, and Class 3 remote-control or signaling circuits and power-limited fire alarm circuits shall be premitted to be wired in accordance with Articles 640, 725, 760, 800." Why is this relevent/interesting? Well, mostly it's not, but Article 640 ("Audio Signal Processing, Amlification, and Reproduction Equipment" defines "Technical Power System" as "An electrical distribution system with grounding in accordance with 250.146(D), where the equipment grounding conductor is isolated from the premises grounded conductor except at a single grounded termination point within a branch-circuit panelboard, at the originaging (main breaker) branch-circuit panelboard, or at the premises grounding electrode." Maybe I'm reading that wrong, but that seems to imply to be incompatible with the idea of "technical power" meaning 60V/120V balanced power. (250.146(D) permits isolated receptacle grounds not tied to the closest panelboard but instead terminating at some central grounding location)

In an additional bit of irony, other parts of Article 640 refer to balanced power as "a seperately derived system with 60 volts to ground" (640.7(B) and 640.9(A)(2)).

Bleh. These NEC/NFPA people could really use a decent techwriter and copy editor. [Mad]

--jhawk
 
Posted by Gordon McLeod (Member # 33) on 01-07-2003, 08:07 PM:
 
On our balanced hookups i use a connector speced by our local huble rep that is a non standard twistlock
 
Posted by Ray Derrick (Member # 1001) on 01-09-2003, 06:15 AM:
 
All that current! I've often wondered why the US chose 120V for local mains distribution when most of the rest of the world chose 220 to 240V - half the current, half the loses, half the copper needed(expensive stuff). You can get electrocuted just as fatally at 120V as you can at 220V so anyone know why the US chose 120V?
 
Posted by Steve Kraus (Member # 476) on 01-09-2003, 07:08 AM:
 
Can be electrocuted. Sure. But far less likely to be.
 
Posted by Richard Fowler (Member # 893) on 01-09-2003, 08:28 AM:
 
With that logic the Jaspanese with 100VAC with no ground should have the longest life [Wink] I have been shocked by 70 V lines....
 
Posted by John Pytlak (Member # 331) on 01-09-2003, 09:40 AM:
 
It's the current that kills, not the voltage (but higher voltages
allow higher currents to penetrate the skin):

Princeton Hazard Communication Guide

OSHA Guideline

Electrocution in Western Australia

India Guide

Ontario Canada Guide
 




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