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#1 DarrylPargeter

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Posted 19 February 2012 - 06:56 PM

Hey Guys,

First time posting on the bored but been larking for a while now.

I have a question I'm in the middle of Pre-production for a new film and we are planing on using a flat for are main location.
I was wondering how to work out how much load you can put on a domestic circuit breaker in the UK.

I looked in books but haven't really found any real useful information at this point in time. If anyone knows how to work out the max load the circuit can take I would be very grateful to you.

Yours
Darryl Pargeter.
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#2 Chris Millar

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Posted 19 February 2012 - 10:15 PM

The circuit breakers themselves are a good source of information...

Say it says 10A - thats 10Amps

P = I.V

In the UK you'll be somewhere in the range of 230V

A sniff of math and spell check:

2.3kW

People will have more detailed info to follow - that's to get you started.
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#3 Guy Holt

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Posted 19 February 2012 - 10:49 PM

.... we are planing on using a flat for are main location. If anyone knows how to work out the max load the circuit can take I would be very grateful to you.


The best way to determine the maximum load the electrical service of a location can support is to look at the main breaker of the service head (main electrical panel.) Domestic wiring is almost always single phase, meaning it has two hot legs that are 180 degree out of phase. A flat would have either 60 or 100 Amps per leg, which means that there would be either 120 or 200 Amps available. While that’s a good amount of power, it is nearly impossible to access it all. The first problem is that it is only available to you in small branch circuits of 15 or 20 Amps. The second problem is that you must balance the load of your lights over the two legs of the electrical service. For these reasons, you end up not being able to utilize large lights or even a lot of the power that is available.

Posted Image
The voltage of opposing legs of a single phase circuit add while the current carried on the legs subtract.


One way to utilize larger lights, or more of the available power, is to step-down a 240V circuit to 120V with a transformer. Common household 240V circuits include Range Plugs, Dryer Plugs, and special receptacles installed for Window Air Conditioners. Like it does with the enhanced 7500W/240V output of our Honda EU6500is Generator, a step down transformer will convert the 240 volts supplied these household 240V receptacles to 120 volts in a single circuit that is the sum of the two single phase legs of 30/50 amps each. Now that you have a larger (60A usually) 120V circuit, you can operate larger lights, or more smaller lights, than you could otherwise.

Posted Image
Master shot of an iRobot commercial lit with a 4kw HMI Par (outside) & 1.8kw HMI Par (inside) powered from a 30A/240V dryer outlet through a step-down transformer/distro. Note: Sunny feel created by 4k Par on an overcast day.


I used this approach to provide GFCI protection for a 4k HMI on a wall outlet on a recent commercial for iRobot (see production stills attached.) The spot contrasted the iRobot Scooba designed to clean kitchen floors to the old mop and bucket approach.

Posted Image
Left: Transformer/Distro plugged into a 30A/240V dryer outlet. Right: 4K HMI Par under rain protection powered by Transformer/Distro


For the mop and bucket approach we had a haggard looking Mom slopping water all over the kitchen floor as kids ran slipping and sliding across the floor. Because we knew water would get everywhere we used one of our 60A Transformer Distros on a Dryer Plug to power a 4K HMI, a 1800W HMI, and some Kinos.

Posted Image
Left: Arri AS18 1800W Par powered from Transformer/Distro. Right: 4Kw and 1800W HMI ballasts powered from Transformer/Distro.


We put a 100A Shock Block like the one pictured below on the load side of the transformer/distro to provide Ground Fault protection inside around the wet kitchen floor. It was a good thing that we did, because it ended up pouring rain that day and so the Shock Block did double duty for the 4k that was outside the kitchen window.

Posted Image
A single 100A GFCI "Shock Block" can provide ground fault protection on wet locations for the entire distro system of a Honda 6500 portable generator when used in-line with a Step-Down Transformer/Distro.


By giving you access to more "house power" through common 240V household outlets, a Transformer/Distro can eliminate the need for dangerous tie-ins or expensive tow generators (use this linik for details.)

Guy Holt, Gaffer, ScreenLight & Grip, Lightng & Grip Rental in Boston
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#4 Adrian Sierkowski

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Posted 19 February 2012 - 10:51 PM

Here in the US, at least, I always make sure to round down my voltages (e.g. our 120V is really 100 for my napkin math (paper amps), so your 230 might as well be figured as 200.) This allows headroom and helps make sure you don't pop power; not to mention simplifying the maths.
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#5 Rob White

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Posted 20 February 2012 - 04:45 AM

In the UK most homes are fed by a 100A breaker which is then divided between the circuits.

Most circuits that feed the plug sockets are rated for 26A, but the sockets themselves are only 13A. In practise this means the biggest light you can plug in is a 2.5K HMI, but you can have two per circuit as long as they are on separate sockets. The number of circuits and how they are arranged is down to an individual building, it'll just take a little bit of investigating with the fusebox!

Hope this helps.
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#6 DarrylPargeter

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Posted 20 February 2012 - 05:38 AM

Okay thank you, sorry about my spelling it isn't a strong point of mine.

the information helps. I've had a look at the fuse box and it say 5amp sockets at 230v, so would I need to change the 13 amp to 5?

as if I'm correct the I should be able to pull 1kW (using paper amps) or 1,150kW (non paper amps)

in terms of changing the Vs from 240V to 120V, I don't think that will be possible as we are working on a very tight budget unless I use this then a US to UK plug.
Would that work or be to unsafe?
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#7 Brian Drysdale

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Posted 20 February 2012 - 07:48 AM

the information helps. I've had a look at the fuse box and it say 5amp sockets at 230v, so would I need to change the 13 amp to 5?

as if I'm correct the I should be able to pull 1kW (using paper amps) or 1,150kW (non paper amps)


I assume the 5 Amp sockets are only the bedside lamp variety, they may have the 5 Amp round pin plugs fitted. You'll need to either change the 13 Amp plugs or make an adapter tail. Don't use more than 1k, I think the largest light I ever put on one was 800 watts, although from memory the only place I've seen them in recent years is in hotel rooms. If the whole house is fitted with them rather than 13 Amp sockets, I'd be careful about the wiring, it could be old.
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#8 Guy Holt

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Posted 20 February 2012 - 08:31 AM

Don't use more than 1k, I think the largest light I ever put on one was 800 watts, although from memory the only place I've seen them in recent years is in hotel rooms. If the whole house is fitted with them rather than 13 Amp sockets, I'd be careful about the wiring, it could be old.


Sorry to have muddled the thread - somehow I missed the fact that the OP was in the UK. In this situation it is important to bear in mind that HMIs and Kino don't follow Ohm's Law (W_VxA) because they have a Power Factor that causes them to draw a greater Apparent Power. For example, the Joker HMI ballasts are not Power Factor Corrected. Their poor Power Factor causes them to use power inefficiently which can lead to unpleasant surprises in situations like this. If we look at the technical specifications for Joker Buglites, we see that the ballast that the Joker 800 uses has a Power Factor of .56. What that means is that it draws 12.5 Amps rather than the 7 Amps you would think using Ohm’s Law (W=VA.) The difference between the actual current drawn by the bulb, 12.5 Amps, and the 7 Amps a 800W bulb should draw using Ohm’s Law (800W/115V=6.956A), is the difference between what is called “Apparent Power” and “True Power.”

If, in this case, you were to measure the actual current (using a Amp Meter) and voltage (using a Volt Meter) traveling through the cable supplying the Joker 800 ballast and multiply them according to Ohm’s Law (VxA= W) you would get the “apparent power” of the bulb (115V x 12.5A = 1437W). But, if you were to instead, use a wattmeter to measure the actual amount of energy being converted into real work (light) by the ballast you would get the “true power” of the bulb which in this case is specified by the manufacturer as 800W. The ratio of “True Power” to “Apparent Power” is called the “Power Factor” of the light.

A favorite analogy electricians like to use to explain Power Factor is that if Apparent Power is a glass of beer, Power Factor is the foam that prevents you from filling the glass all the way up with beer. When lights with a low Power Factor are used, the distribution system must be sized to supply the Apparent Power (beer plus foam), even though only the True Power (beer) counts. With a Power Factor of .56, you must take into account that the Joker 800 ballast draws considerably more power (1437W) for it’s true power output of 800W.

Used on wall outlets in the US, this relatively inefficient use of power is negligible because the power draw of the Joker 800 fits easily in a standard wall circuit. However, the greater Apparent Power of lights with a poor Power Factor must be factored in situations like this or when using portable generators. For instance, you would think that you could operate a Joker 800 on a simple two stroke 1000W generator. But, in fact, you would overload the generator because the “continuous load” rating of the All Power America 1000W Generator sold at Walmart is only 850W and the actual load of the Joker 800 is 1437W. The greater Apparent Power of Lights with a poor Power Factor is not the only consideration when operating them on a generator. When you use lights sources like HMIs, Kinos, CLF lamp banks, and even LEDs, on generators it matters not only what type of ballasts the light uses, but also what type of generator you use to power it. The harmonic currents that ballasts with poor Power Factor, like the Joker 800 electronic ballast, kick back into the power stream can have a severe adverse effect on the power waveform of some generators. Use this link more detailed information on Power Factor and Power Factor Correction.

Guy Holt, Gaffer, ScreenLight & Grip, Lightng & Grip Rental & Sales in Boston
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#9 Rob White

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Posted 20 February 2012 - 11:41 AM

Okay thank you, sorry about my spelling it isn't a strong point of mine.

the information helps. I've had a look at the fuse box and it say 5amp sockets at 230v, so would I need to change the 13 amp to 5?

as if I'm correct the I should be able to pull 1kW (using paper amps) or 1,150kW (non paper amps)

in terms of changing the Vs from 240V to 120V, I don't think that will be possible as we are working on a very tight budget unless I use this then a US to UK plug.
Would that work or be to unsafe?


Are they 5A sockets, or a 5A circuit? If you look at the individual breakers they will have a rating on. 5a sockets are typically only used for table lamps etc that are controlled by the lightswitches in a room. You could always post pictures if you aren't sure.

If you are going to 120V kit, then you'll need a suitably rated transformer. The one you posted could only run 100w. Depending on what lights you're using; it's probably a lot easier to hire them from a UK company - you won't have to worry about transformers and adaptors then.
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#10 DarrylPargeter

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Posted 20 February 2012 - 01:49 PM

I believe 5A circuit, though not sure, I will have a better look on Friday when we next vist the location, and post photos of the fuse box, the location is a new build but we would be using what is the showroom at this point in time.
I don't plan on using anything over 800W on the day, and 800 at a push if its an overcast day.

to Guy Holt thanks for the info about power factors, do you happen to know what a 2ft Double Kino flo will be drawing, as I've tried looking for the information myself but haven't have had much luck other then the tech spec on Kinos website, which leaves me just a tad confused.
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#11 Mark Dunn

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Posted 20 February 2012 - 02:08 PM

Any UK domestic circuit with square-pin plugs will run a blonde or redhead. Google tells me that Kinoflos are only a couple of hundred watts so they will barely draw a couple of amp. You're right to ask but unless it's in a really old house don't worry.
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#12 Guy Holt

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Posted 20 February 2012 - 10:18 PM

... the tech spec on Kinos website, ... leaves me just a tad confused.


The tech specs on the Kino website for the current drawn by their T12 fixtures (the 2’ & 4’ single, double, and four bank fixtures) are confusing because, like the Joker HMIs, their ballasts are not Power Factor Corrected, which means that they draw more power (their “Apparent Power”) than the wattage of the bulbs that they use (their “Real Power.”) I’m not certain about the 2’ double, but a 4’- 4 Bank ballast with four 75W tubes draws more than the 300 Watts (4x75W=300Watts/120V = 2.5 Amps ) that you would think according to Ohms Law. With a Power Factor of .54, it in fact draws 4.6 Amps or has an Apparent Power of 550W. In other words, it draws nearly twice the power that a Power Factor Corrected ballast would draw to power the same four 75W tubes.

The greater Apparent Power of lights with a poor Power Factor is not the only consideration when using a number of them on a location or operating them on conventional generators. Of equal importance, is the Harmonic Noise that they kick back into the power stream because it can severely affect power quality. For instance, on their website Kino Flo cautions users of their older style fixtures that use T-12 tubes, that the ballasts “will draw double the current on the neutral from what is being drawn on the two hot legs. On large installations it may be necessary to double your neutral run so as not to exceed your cable capacity.”(http://www.kinoflo.com/FYI/FAQs.htm#2). The Harmonic Noise that ballasts with poor Power Factor kick back into the power stream can also severely limit the total number of lights that can be reliably operated on conventional generators (use this link for more details. )

Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip Rental and Sales in Boston.

Edited by Guy Holt, 20 February 2012 - 10:20 PM.

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#13 Brian Drysdale

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Posted 21 February 2012 - 06:07 AM

Just to add that the 800 watt light that we used in the 5 Amp socket was a Redhead, rather than a HMI.
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#14 DarrylPargeter

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Posted 21 February 2012 - 06:34 AM

Hey Guy Holt,

how do you work out the Power Factor of .54 and then work out the Apparent Power of 550W?

and Brian Drysdale thanks for that bit of info
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#15 Guy Holt

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Posted 22 February 2012 - 08:16 AM

... how do you work out the Power Factor of .54 and then work out the Apparent Power of 550W?


I came up with a PF of .54 for the Kino 4-Bank Select ballast by plugging the following figures into the equation for Power Factor below.

Posted Image


The “True Power” of the system (expressed in the equation as KW) is the sum of the wattages of its four 4’ T12 tubes or 300W (75Wx4). The “Apparent Power” of the system (expressed in the equation as KW + KVAR) is what you would get if you were to measure the current (using a Amp Meter) and voltage (using a Volt Meter) traveling through the cable supplying the Kino ballast and multiply them according to Ohm’s Law (W=VA). According to the technical specifications on Kino’s website the 4 Bank Select ballast draws 4.6A at 120V making the Apparent Power 552KVA (4.6A x 120V = 552.) Which makes the Power Factor (expressed as PF in the equation) .54 (300W / 552KVA = .54), or the Kino ballast draws nearly twice the power of an incandescent lamp to generate the same 300W of lights.

Posted Image


Use this link for a more detailed explanation using electrician’s favorite beer analogyillustrated above. If you are wondering where all that extra power is going – it is going into the generation of harmonic currents which can distort the voltage waveform of the power in the distro system and can build to dangerous levels on the Neutral of the system. The Harmonic Noise that ballasts with poor Power Factor, like the Kino 4 Bank Select Ballast, kick back into the power stream can also severely limit the total number of lights that can be reliably operated on conventional generators (use this link for more details.)


Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip Rental and Sales in Boston.
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#16 DarrylPargeter

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Posted 23 February 2012 - 09:47 AM

so if I understand it right then for a Double Kino at 230V

at 4ft would the P.F =.46 and the Apparent Power is 322W and would the 2ft would the P.F = .38 and the Apparent power be 207w?

I believe my calculations are right, I just what to make sure.
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#17 Guy Holt

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Posted 23 February 2012 - 08:12 PM

so if I understand it right then for a Double Kino at 230V at 4ft would the P.F =.46 and the Apparent Power is 322W and would the 2ft would the P.F = .38 and the Apparent power be 207w?


If you are wondering where all that extra power is going – it is going into the generation of harmonic currents which can distort the voltage waveform of the power in the distro system and can build to dangerous levels on the Neutral of the system. This is why Kino Flo, on their website, cautions users of their older style fixtures that use T-12 tubes, that the ballasts “will draw double the current on the neutral from what is being drawn on the two hot legs. On large installations it may be necessary to double your neutral run so as not to exceed your cable capacity.”(http://www.kinoflo.com/FYI/FAQs.htm#2).

Posted Image
Left: Pkg. of 2-1200 HMI Par w/ non-pfc ballasts & Kino Wall-o-Lite powered by grid power.
Right: Same Lighting Pkg. powered by conventional AVR Generator (Honda EX5500)
Note different effect that the same non-linear load harmonics have on grid power and power from conventional AVR generator.


The distortion of the voltage waveform that harmonic currents can cause (Harmonic Noise) can also severely limit the total number of lights that can be reliably operated on conventional generators (see voltage waveform distortion above.) Use this link for more details on the source of harmonics and how to counteract their adverse effects.

Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip Rental and Sales in Boston.
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#18 DarrylPargeter

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Posted 24 February 2012 - 04:55 PM

Okay so I went back to the location today and checked out the fuse box.

the fuse box is 100A at 230V giving an overall output at 23,000kW and it has two circuits both at 13A, 230V giving 2,990kW.
first of is that right? and secondly if I put 2,000kW (which I shouldn't be) into the circuits would that trip the fuses? or would it be okay as both can take more?

heres the fuse box in photos just in case I missed something:
Right hand side of fuse box
left hand side of fuse box
whole fuse box

sorry about the links to the photos but when I resized them you couldn't make out any of the detail.
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#19 Rob White

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Posted 25 February 2012 - 01:45 PM

Okay so I went back to the location today and checked out the fuse box.

the fuse box is 100A at 230V giving an overall output at 23,000kW and it has two circuits both at 13A, 230V giving 2,990kW.
first of is that right? and secondly if I put 2,000kW (which I shouldn't be) into the circuits would that trip the fuses? or would it be okay as both can take more?

heres the fuse box in photos just in case I missed something:
Right hand side of fuse box
left hand side of fuse box
whole fuse box

sorry about the links to the photos but when I resized them you couldn't make out any of the detail.


The Lounge sockets are on a 32A circuit, so you can run just over 7.3kW, but no more than 3kW (MAX) per socket.
The Bedroom is a 20A circuit, so that's 4.6kW total - again no more than 3kW per socket.

If you put 2,000kW it'll certainly blow! Though I guess you meant 2,000w. In which case you'll be absolutely fine.
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#20 DarrylPargeter

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Posted 25 February 2012 - 02:09 PM

Yes i do mean 2,000W...

so from that I'm guessing that the B 32 and B 20 means the amps on the fuse?

though I'm some what confused I've been told that kW = anything over 1,000W. and if thats the case I've been told something wrong which isn't good as I'm dealing with electricity.
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