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Author Topic: Lamphouse wire size and type Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 01-02-2010 10:51 PM                     The Coleman brand cable we use is indeed 600V rated and is "welding" cable.  |  IP: Logged Ian Parfrey Phenomenal Film Handler Posts: 1049 From: Imbil Australia 26 deg 27' 42.66" S 152 deg 42' 23.40" E Registered: Feb 2009 posted 01-03-2010 01:10 AM                     John. quote: John Hawkinson Why do you ask? I guess we can measure it easily enough. I'm just interested in how far a high amperage DC run can be without too much drop. One cinema I worked at had Irem's on the back of Bauer U3's and 4's. The run there was around 55-60' but I can't recall the drop over that distance.  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 01-03-2010 02:27 AM                     Well, I'm not totally sure what you mean. You can go as far as you want to go and take as much drop as you want to drop. Problems you run into: #1 (obvious) if you get too much drop, then the voltage required on your rectifier to make the voltage you need at the lamphouse may be too much, and your rectifier can't support you. #2 (subtle) if you have a lot of drop, that means you have ohmic heating (I^2*R) in your conductors, and as their temperature rises, then their resistance rises, leading to greater voltage drop. And for a typical rectifier, that is essentially maintaining a fixed output voltage, that means as the resistance changes, the effective voltage seen by the lamp drops over time, and that means the current draw from the lamp drops over time. So you could see, e.g., a lamp that spikes to 90A for the first two minutes and then falls back to 70A once the wires start cooking. (Obviously this is not a great place to be.) Louis: I'm a little puzzled by your inrush concerns. What's the problem with overcurrenting the conductors for a few milliseconds? They won't heat up enough to be a problem, nor will they appreciably limit the current. At least, that's not been my experience and I don't see why it should happen fro ma theoretical standpoint. I assume you've seen a practical example of this behavior? --jhawk  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 01-03-2010 09:30 AM                        I have no idea what the cable electricians used in our park installation other than it looks to be about #04, very flexible so I am assuming fairly high count strands with the run being about 50 ft from the IREMs to the lamphouses. They use twistlocks on at the rectifiers. We are burning 4500w. Thing is, this wire does get warm to the touch and it stays that way as a kind of steady-state, never getting hot. This always worried me figuring there's more resistance than there should be, but it has never caused any problems -- voltage reads fine pulling correct amperage and it's been running that way since the installation so my assumption is that it ain't broke..... No indication anywhere along the away that there is heat deterioration at the contact points, either in the lamphouse or at the large twist pigtails (it's all portable so the lamphouse has to be able to disconnect easily for break-down). The pigtail connections get warm as well. Do you think I should be concerned? Should this cable be replaced with a larger guage?  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 01-03-2010 10:23 AM                     The cables will get warm...I would definitely get it to #2 or larger though for 4500 watts. Ask your electrician what he should use on 155A DC....likely he won't think #4. Steve  |  IP: Logged John Hawkinson Film God Posts: 2273 From: Cambridge, MA, USA Registered: Feb 2002 posted 01-03-2010 11:38 AM                     Frank: you should measure the voltage drop under load and see...measure the DC voltage at the rectifier, measure again at the lamphouse. How much do they differ? Also, measure across connection points...remember that if you have 0.1 ohms of resistance, well at 155A amps that'd be 15 volts! So a little adds up. And it's easy to get a hundredth of an ohm here or there with a loose connection... Cables should have their designation printed on the exterior. It can be tough to tell wire gauge by diameter, though. For instance, #4 THHN is .318" outside diameter. But #4 welding cable might be .380" from one manufacturer or 0.420" from another. And while you got there #2 THHN was was 0.378"... When you say pigtails, you mean the Cam-Loks in your picture? It sounds worrysome to me if those are warm, yeah... --jhawk  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 01-03-2010 03:16 PM                     quote: Gordon McLeod actually welding cable must be in free air as its insulation is not rated for in flex we buy what is CSA rated entertainment cable now days for our dc leads In nearly 35 years I've only encountered a handful of locations in the USA where open DC cables were allowed. Even the Imax and Iwerks 400 amp cables(welding type)were installed in flex or conduit. Mark  |  IP: Logged Phil Hill I love my cootie bug Posts: 7595 From: Hollywood, CA USA Registered: Mar 2000 posted 01-03-2010 03:23 PM                  Mark is correct. All 1570 15kW installs that I did with a "remote" Rectifier, code required the cables to be in metal conduit. I used 4/0 600V Carol SUPER VU-TRON WELDING CABLE cable. Ummmm, jhawk... NO THHN! HA!  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 01-03-2010 07:14 PM                     In almost every theater here on Long Island, they are NOT installed in any kind of covering.  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 01-04-2010 11:49 PM                        Yah, John, the cam-locs in the pic -- they do get warm, but as I said, nothing seems unusual, such as any discoloration you might find if there were excessive heat at the contact points either in the lamphouse or at the cable connection clamps in the rectifiers. Although, you might recall we did have that relay in one of the IREMs blow up on us a few summers ago. After that little fun evening, now when we pull everything out of storage in June, I routinely check the all the contacts there and in the lamphouse for any oxidation and corrosion -- everything lives in storage all year round except for the summer festival. No idea about the voltage drop -- it will have to wait until next summer for me to test it.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 01-05-2010 08:22 AM                     quote: Richard May In almost every theater here on Long Island, they are NOT installed in any kind of covering. I think codes were more a little more liberal with allowing that not even too long ago. It was also common in the Chicago area on locally installed rectifiers. Codes regarding arc and xenon have tightened up a bit in the last 5 to ten years or so. It is also highly likely the inspector had no clue as to what he was looking at... Frank, They will get warm... that is ok... hot is not ok!  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 01-05-2010 12:10 PM                        Never had an inspection at that site, Mark, it's all "portable" and that seems to allow for great leeway. Plus, it's city owned & operated. The city, unfortunately, doesn't inspect itself, or when it does, it might write up a violation, but it go nowhere; it simply vanishes. In our theatre we had a major fire that gutted our entire office complex of 10 offices and a work islands and conference rooms. This suite has exits directly into one of the theatre's lobby and directly on top of another theatre. In a building housing four theatres which had a major fire, you would think there would be even a modicum of attention paid to the building's fire alarm system. Not so -- The announciator system has every trouble light lit and the alarm siren and strobe were going off routinely two and three times a week giving false alarms. The solution that they came up with? They disabled the system....in a building that had already had a fire. The system has been disabled for at least two years now. And the Fire Department KNOWS about it because I personally went out to a fire truck that was parked outside our theatre one day and ask one of the firemen who was standing outside the truck, who do I speak to about a serious violation, pointing to the building that still had smoke marred bricks above each of the windows. The captain stuck his head out of the truck and said, "You talk to me. Dave and Tommy, you go with this guy." I took them to the fire control panels, showed then all those pretty red LEDs lit up and the key switch set on DISABLE. They wrote it up and seemed very concerned, but that was the last I heard of it. My solution? -- I just keep a fire extinguisher next to my desk at all times & know exactly what exit door closest to me I'll be running out of the minute I smell the slightest wiff of smoke. clear the place in 5 minutes.  |  IP: Logged Richard Hamilton Phenomenal Film Handler Posts: 1341 From: Evansville, Indiana Registered: Jan 2000 posted 01-05-2010 01:47 PM                     quote: Frank Angel I'll be running out of the minute I smell the slightest wiff of smoke pussy!  |  IP: Logged Phil Hill I love my cootie bug Posts: 7595 From: Hollywood, CA USA Registered: Mar 2000 posted 01-05-2010 03:58 PM                  Rick, you're terrible! HA!  |  IP: Logged Ian Parfrey Phenomenal Film Handler Posts: 1049 From: Imbil Australia 26 deg 27' 42.66" S 152 deg 42' 23.40" E Registered: Feb 2009 posted 01-05-2010 04:54 PM                     Now, a REAL TECH would smell the smoke, empty the corporate drinks cabinet, consume contents of said cabinet, personally extinguish the conflagration using expended contents of cabinet contents, ensure the safe evacuation of all the cute co-workers and bask in the glory and physical adoration from the womenfolk in the building. But hey, we can't all be Angels. Seriously, Frank has done all that is possible and within his power to bring his concerns to the appropriate authorities, and it is no reflection on Frank that his concern for safety is overwritten by the dumb-ass inanity of governmental institutions...these same institutions, co-incidently, that would come down like a ton-of-bricks should any of us even think of doing the same thing that they allow themselves to do (and get away with). If I was Frank, his own actions would be safely diarised and stored offsite for possible future use when the going gets nasty. So, on to my movie review for this all-action crash bang wallop 3D spectacular.... CINEMA: Frank's Theatre AUDITORIUM: 1, if still standing. PRESENTATION: 35mm (Yay- real sprockety-type perforated plastic type stuff) Dobly Digital audio - "Does that sound like flames!?" PRESENTATION PROBLEMS: None, except some smoke haze in the projection beam. MANAGERIAL PROBLEMS: Now, where do we start! RATING: Technician's concern for safety aspect - 8 stars out of 4 RATING: Management's concern for safety aspect - 0.1 stars out of 8 Comments: What can one say about the progress 3D has made to the Disaster genre of movie making? The visual effects of the flames licking the ceiling, the density of the smoke in the office alcoves, the charred remnants of co-workers all meld to produce an extremely powerful experience that makes one want to leap into the screen and grab those moronic, brain-dead beaurocratic dum-asses and throttle them. One can only hope that this plot will remain the imagination of a creative filmmaker and never cross that third wall into the realm of reality.  |  IP: Logged

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