House power: amps and fuses

[John Sprung]

It turns out the wiring was 16 Kilovolt

<{POST_SNAPBACK}>

That's interesting. 16kV is an oddball. Most HV around town is 34.5 kV, with 13.8 in older areas. I googled around and found a used utility transformer web site, they had hundreds for sale, but nothing at 16 kV. Did you look around for transformers and positects? They're a pretty good indication that you're looking at some high voltages. Another clue is that a proximity tester -- the ones about the size of a large sharpie -- will go off at a significantly larger distance from HV. They'll even beep in your shirt pocket. It's really strange to find that kind of voltage in a box in a warehouse, especially without any transformers nearby.

 

(Oh, BTW, another thing: Never never never backfeed any building electrical system from a generator. Quiz: Why?)

 

 

 

-- J.S.

Edited April 1, 2005 by John Sprung

[Paul Bruening]

Hello David,

 

I'm getting fine use out of my putt putts. I build blimps out of square tube steel and double box them out with ordinary, duct grade, galvanized sheet metal. I scrounge foam from the cushions of discarded furniture on the streets then place it between outer and inner walls. Then I route the exhaust through a car muffler and into a chamber made of expanded steel and glass wool baffles. I mount two baffled, high temp, high volume service fans to pull air through the unit. I get 5,200 watts out of each unit. They run steady and deliver dependable volts. Most of all, they are by far the quietest units I've ever encountered.

 

Just a thought.

[Phil Rhodes]

Hi,

 

Just for the record, the majority of local mains distribution in the UK is at 11KV, which is the voltage it's generated at. National distribution (another thing made possible by the small geographical size of the place) may be at up to 132 or 500KV.

 

Needless to say any of these will cause you to explode like an overloaded fuse.

 

Phil

[Luke Prendergast]

like this guy ---->

[Michael Morlan]

Ive often wondered about this practice. The problem is 220v stove outlets are fed by 10/3 that means 10 gauge wire(rated @30amps) 3wire (red,black & white). the red and the black each 'hot' at 110v and the white is common. So if you split up the red and black to give you two legs each 110v then you are still running both circuits off a single common wire. Given that the breaker only protects the hot wires you have a great potential for damaging that common wire.

<{POST_SNAPBACK}>

 

Remember that, with a dryer hookup as described in this thread, were you to run an even load on the red and black 110v lines, there would be NO load on the common since the red and black lines are 180degress out of phase and cancel each other out as they drain on the common.

 

I have an article coming up in the April issue of DV Magazine that addresses powering sets from household systems. It addresses everything short of a distro tie-in. In the interim, the precursor article is still on my website until the print version is released:

 

http://michael-morlan.net/pages/learning/l..._management.htm

 

Michael

[John Sprung]

National distribution (another thing made possible by the small geographical size of the place) may be at up to 132 or 500KV.

<{POST_SNAPBACK}>

In the U.S. we have a lot of 138 kV, and 500 kV even on old lines built in the 1930's. (WPA, I'd guess.) The highest voltage I've heard of is the 750kV DC line from the Dalles in Oregon down here to Sylmar. SMPTE had a tour of the Sylmar station a few years back, unfortunately I didn't get to go.

 

 

 

-- J.S.

[Chris Keth]

Just to give you an idea how dangerous inexperienced people doing tie-ins is, the people at my school joke that it's a 2 person job: 1 to do the tie-in and the other standing by with a 2x4 to beat you off of the wires when you can't let go.

 

 

 

It's a joke put that way but it's a damn dangerous thing to do when you don't know what you're doing.

[Michael Morlan]

I have a healthy dose of timidity when it comes to any form of electricity.

 

As a young audio engineer, I got caught in a 220v differential between legs of a household breaker box. It started innocently enough - playing bass guitar and reaching for the mic. Little did I know the bass amp was ground-lifted on one half of the building and the mic mixer on the other. Once I was caught, there was no letting go. I thought I said "Oh $#@%, get this thing off me!" Nope. I thought I opened my hand from the mic. Nope. As I began to tip backwards and the snow started to fill my vision from the edges, I realized I was going to die. My breathing was arrested, my heart was in danger of arrest with the current passing right through my chest. I was a goner...except the band was still in the room and recognized what was going on. Several attempts to yank the bass out of my hand failed. Finally, one of them got the bright idea to simply pull plug from the bass and I was released.

 

And THAT was from a relatively light current between a bass amp and mic mixer. Imagine what would happen if you got hold of a 100amp hot leg in a household breaker...or worse!

 

Ironic that I'm making a partial living as a gaffer now! :blink:

 

When it comes to hot tie-ins, I am considered a "qualified person" according to the National Electrical Code. I am trained by a certified engineer to perform specific tie-ins. I can legally perform tie-ins with absolutely familiar situations. If I encounter a breaker box I've not seen before, I go straight for the phone and hire my mentor to do the patch.

 

I don't want to die, 'cause I've already used up my chance.

 

Michael

Edited April 3, 2005 by mmorlan62

[Paul Bruening]

Hello Michael,

 

Well done on the power article on your site. Do you have a feature in mind in the near future? We're gearing up to shoot a love story this summer. I snagged a Mitchell BNC 2 perf. I could use a DP. All of the budget is going into gear or down the throat of the camera. However, we can bunk, feed, and cover your gas. Would you be willing to entertain the notion? We're also putting together a 50 x 200Gig SATA array and 4 x 3800+ render farm. Is this interesting to you? My contact info is below. Please let me know either way.

 

Thanks,

Paul :)

[John Sprung]

And THAT was from a relatively light current between a bass amp and mic mixer.  Imagine what would happen if you got hold of a 100amp hot leg in a household breaker...or worse!

<{POST_SNAPBACK}>

The results would be pretty much the same. Unless a breaker trips, it doesn't matter at all whether it's rated for 15 Amps or 400 Amps. It's the voltage and the impedance of the load -- in this case your body -- that determines how much current actually flows. You can dip a teaspoon into a soup bowl or a swimming pool, and you'll still only get one teaspoon of liquid.

 

In the situation you describe, the equipment ground was lifted on both devices, and hot was shorted to the chassis on both devices. Lifting ground on everything all over the place is a bad and dangerous practice. The right way to go is to plug everything in, check it, and only put in a ground lifter if you have a loop problem. Both sides of the lifter should still be grounded, it's only the loop that you want to break. Metal that's left floating is not only dangerous because it won't trip a breaker if it gets shorted to hot, it's also a path to spread noise around rather than grounding it out.

 

If an audio setup is small enough to all run off of one plug strip, that's the best way to go. It frees you from being part of the path for other crap in the building's electrical system.

 

 

 

-- J.S.

[Phil Rhodes]

Hi,

 

I carry several somewhat-illicit ungrounded mains patch leads, all of which have been useful at some point to take hum bars out of various bits of video equipment. Generally created on the spot with a bit of judicious screwdrivering, but all clearly labelled and used as a last resort.

 

Phil

[Michael Morlan]

The results would be pretty much the same.  Unless a breaker trips, it doesn't matter at all whether it's rated for 15 Amps or 400 Amps.  It's the voltage and the impedance of the load...

<{POST_SNAPBACK}>

 

Right you are, sir. I'm still not sure whether I was getting the full 220v or something after a step-down transformer. I never went back to check. :D Sure felt similar to a couple of other brief 110v shocks I've taken.

 

I'm all for appropriate use of ground-lifters. Got saved the other day by a properly grounded Mole Baby in an Austin home. A hanging practical was apparently shorting to frame and, while moving a light, I touched the frame of the practical with the Baby. POP goes a breaker. Didn't feel a thing.

Edited April 4, 2005 by mmorlan62

[Rolfe Klement]

bringing this thread back to life...

 

I have a healthly respect for the "evils of electricity" and have had some serious shocks - once I was unscrewing a power point from the wall when I was electrocuted because the screw holding the power point in the wall was live - the live had come undone had slipped off and got caught up on the screw!

 

What is the max load per circut in the uk for a normal 13A power point? The reason I ask is I was doing a shoot (I was not the gaffer )and I realised we had a 2.5kw HMI, a 1.2 HMI and some other stuff all running off one plug. I asked the gaffer to move the load around and we wound up running a cable to another flat and using their power for half of the load.

 

But everything seemed OK when we were running so much power off one plug. I was once told by one of the "old grey gaffers" that the max load per plug in the UK was about 3500W - but if you check the circuts from the mainsboard you can run 3500W per circut - so if you have one circut upstairs and one downstairs you can run 7kw total but not exceed 3.5kw on one circut

 

Assuming the circut breakers were working what are the negative effects of overloading - i.e. plugging a 5kw into a wall socket - are the cable runs heating up in the wall? or will it trip out before that happens etc?

 

Basically another reason for my asking is I now have built my 4.8kw softlight - with 4 seperate 13A plugs - each plug connected to 1200W (6 x 200W) of parallel wired tungsten light (so 4 x 1200W = 4800W) - what would be the best way to use it in a normal UK house

 

thanks

 

Rolfe

[Stephen Williams]

bringing this thread back to life...

 

What is the max load per circut in the uk for a normal 13A power point? The reason I ask is I was doing a shoot (I was not the gaffer )and I realised we had a 2.5kw HMI, a 1.2 HMI and some other stuff all running off one plug. I asked the gaffer to move the load around and we wound up running a cable to another flat and using their power for half of the load.

 

 

Hi,

 

In the Uk the 13 amp sockets are connected as a ring main, rather than a spur. This means the wall sockets join togther and are connected to the fuse box at both ends.

 

Mark Roberts Motion control make use of this with their Flair System that drives a Milo. At peak acceleration with model movers etc the system can easily draw 25 amps. By plugging in 2 x 13 amp plugs next to each on the same phase. The system can therefore easily be connected in household locations. Ring mains are usually fused at 30 amps!

 

Stephen

[Michael Collier]

how many circuts does the house have? I have run 2k off one circut, then brought a long 10g extension cord up the stairs from another room and put another 2k. I have actually been using 3 circuts at once. I just check the master breaker and see what the house is rated at, and make sure I dont overload that or overload each individual circut (120v[measured] 20A circut usually)

 

I have never had a need for larger than 2k inside, but theoretically--and you electricians can tell me for sure--couldnt you take power from two circuts, run that into a distro box that puts the electricity to the lights in parralell, essentially giving the electricity two paths to go from the breaker box. My assumption is that half would go one way the other half the other (assuming line resistance is equal) and when reconected each circut would bear half the load of the light, allowing for a 4k light to be used.

 

This is assuming the electricity is in phase from one circut to another, but I cant imagine one house having different phases between two circuts. [my grandpa, an engeneer, told me a story once about when he was in school learning how to do basicly this, but with two industrial generators, and some kid messed up a setting putting the phases off 180degrees, with big gennys he said it was quite a light show after they flipped the switch]

[Brian Drysdale]

Hi,

 

In the Uk the 13 amp sockets are connected as a ring main, rather than a spur. This means the wall sockets join togther and are connected to the fuse box at both ends.

 

Mark Roberts Motion control make use of this with their Flair System that drives a Milo. At peak acceleration with model movers etc the system can easily draw 25 amps. By plugging in 2 x 13 amp plugs next to each on the same phase. The system can therefore easily be connected in household locations. Ring mains are usually fused at 30 amps!

 

Stephen

 

You can find a rough lay out for the UK here. http://www.diydata.com/planning/ring_main/ring_main.htm

 

The 13 amp cooker socket is often used because it's on a separate circuit. The BBC's old basic standard lighting kit that the lighting electricians used to bring was 2 x 2k blondes and 4 x 800 watt Redheads and there was never any problems in a modern house. You can plug a 2.5k HMI straight into the wall. Just check that you're not overloading each socket (the 13 Amp fuse will blow).

 

With a domestic mains tie in the biggest light is a 4k HMI or 5k tungsten. Health and safety will require an electrician for this and they'll keep an eye on the load.

[Stephen Williams]

You can find a rough lay out for the UK here. http://www.diydata.com/planning/ring_main/ring_main.htm

 

Hi,

 

Thank you for the link.

 

Stephen

[Rolfe Klement]

great link - thanks

 

I spoke to a gaffer and he said you must be very careful using multiple circuts because you can get a 440V difference and by law live wires from 2 seperate phases of an electrical supply cannot come within 6ft of each other.

 

Because I would be using a different ring circuts (one upstairs and one downstairs) does that mean I an using different phases (most UK houses have a 3 phase supply) and therefore could run into double voltage problems

 

thanks

 

Rolfe

[Stephen Williams]

great link - thanks

 

I spoke to a gaffer and he said you must be very careful using multiple circuts because you can get a 440V difference and by law live wires from 2 seperate phases of an electrical supply cannot come within 6ft of each other.

 

Because I would be using a different ring circuts (one upstairs and one downstairs) does that mean I an using different phases (most UK houses have a 3 phase supply) and therefore could run into double voltage problems

 

thanks

 

Rolfe

 

Hi,

 

In Switzerland it's 3 phase everywhere from domestic kitchens and all studios! The locals don't worry or take any special care, it amazes me. In a studio the phases are mixed even down the same wall! What I try to do is have no 2 lights near each other on the same phase so you can't touch items on different phases.

 

Most Important check that all the EARTH's are CONNECTED. It will Save Your LIFE!

 

Stephen

[Rolfe Klement]

I had a brief read of the riveting lEE Regulations, BS 7671, chapter 6.2.2 - Diversity and it agrees with what Bryan was saying - so as long as you are on a ring circut - and not a spur - you should be able to technically plug 2 x 2500 w

 

that was a fun riveting read - more here http://www.tlc-direct.co.uk/Book/6.2.1.htm

 

 

thanks

 

Rolfe

[Stephen Williams]

I had a brief read of the riveting lEE Regulations, BS 7671, chapter 6.2.2 - Diversity and it agrees with what Bryan was saying - so as long as you are on a ring circut - and not a spur - you should be able to technically plug 2 x 2500 w

 

Rolfe

 

Hi.

 

Exactly!

 

Stephen

[Brian Drysdale]

great link - thanks

 

I spoke to a gaffer and he said you must be very careful using multiple circuts because you can get a 440V difference and by law live wires from 2 seperate phases of an electrical supply cannot come within 6ft of each other.

 

Because I would be using a different ring circuts (one upstairs and one downstairs) does that mean I an using different phases (most UK houses have a 3 phase supply) and therefore could run into double voltage problems

 

thanks

 

Rolfe

 

It would be extremely rare to have a 3 phase supply in a domestic house in the UK. They're always single phase. However, you will get 3 phase supplies in industral premises, but these are usually well marked. You may find that parts of a plant are on a different phases.

 

However, this doesn't apply to other countries. Here's Germany as an example:

 

http://www.jpoc.net/countries/germany/wiringandplugs.html

Edited December 16, 2005 by Brian Drysdale

[Stephen Williams]

It would be extremely rare to have a 3 phase supply in a domestic house in the UK. They're always single phase.

http://www.jpoc.net/countries/germany/wiringandplugs.html

 

Hi,

 

Converted flats in the Uk may well be on different phases, so be careful if you plug in 'next door'

 

Electric Cookers in France & Germany can usually be connected to single or three phase power supply. It explains how graphically on the back of the appliance.

 

Stephen

[John Hall]

I thought some of you might get a kick out of this.

 

I found this box in the basement of the studio while looking for some Socapex splays.

 

 

Whats inside? The most dangerour piece of electric equipment ever!!!

 

 

As you can see, it has three jumper cable-like clamps, presumably to connect to the lines in the box.

The joy cable is very thin, not 6 gauge, maybe 8.

There was a very dodgy looking dief in the the case as well, it was the only thing on this rig that has any sort of breaker. I hope no one ever connected a 5K to this joy!

 

 

The picture didn't turn out very good, but here is an idea of how thin the wire is. And yes, it is wrapped in electrical tape.

 

It's shocking (no pun intended) to think anyone ever used this rig.

 

If you want to hear some scarry (but hilarious) stories, just talk to some old gaffers about the wildest things they've ever done. Guys tying into lamp posts, an old box in a 100 year old church basement. Even 20 year veteren trying to tie-in whilst standing on a full apple in a half-apple's deep water (he was eventually convinced to rent a genny).

The thing is, as crazy as they sound, these guys knew what they were doing. And they are a lot less likely to get fried then some young filmmaker doing a standard tie-in to a standard household service (except maybe the guy in the flooded basement).

 

I disagree, however, that a certified electrician should be required to do a tie-in. If you've been shown how to do it properly then it's a very straight forward procedure that any best boy or even electric should be qualified to do.

 

Here is a photo of a properly done tie-in to a two-phase 100amp service (similiar to a household service). The tie-in cables (double-ought wire)are connected to the first and third connections (the middle being neutral) to provide 220v power to a mobile TV-Truck.

 

 

That being said, there is NO WAY that an indie filmmaker should attempt to do this.

[David Mullen ASC]

I disagree, however, that a certified electrician should be required to do a tie-in.

 

I believe it's the law actually in L.A. but I'm not positive.