On 26/06/2014 12:36, wrote:
On Thursday, June 26, 2014 10:43:55 AM UTC+1, wrote:

Hi All,

I am just looking at buying a floodlight and was having a look at the LED models now on offer (it's to be used at a camp where the energy budget is LOW (45A MCB on the main supply cable

that's huge

Certainly enough to support ~10kW continuous load and briefly higher peaks.

and we need to run a small PA system,

couple hundred watts?

Probably less unless it is disco night when they always seem to wind the
wick up until it hits the end stop and clipping ensues.

house lighting for a Marquee (3 x twin tube flourescents at 110W per luminaire is what i'm thinking), hopefully a (this) flood for the "stage" an urn for tea and coffee,

2-3kW presumably

small water heater for the sink and basin taps,

?

Probably also 2-3kW although you can get slower highly insulated ones
that make a volume of warm water and hold it at temperature. This works
well until someone runs the tap continuously to get it nice and hot!

We have on in our downstairs VH kitchen.

occasional use of twin hob Baby Belling sytle cooker

typically 3kW with interlocked elements

Microwave or combo oven probably more useful.

and George Forman type grill(s).

1-1.5kW?

Even with diversity, I think it's going to be tight!).

Well, if you interlock prioritised loads it wont be hard at all. What I mean is decide on a list of load priorities, and automatically shed lower priority loads when enough power isnt there to run them. Its possible to run an entire flat on a 5A feed that way, albeit with compromises. DAMHIK.

Basically just ensure that the ovens and the hot water are never on
together and you should have enough supply margin. Have a plan or
detailed instructions on what to do if the circuit does trip.

(as sure as eggs are eggs someone will bring in extra kettles for a big
event and just plug them in without even thinking about it)

Its best done automatically with some electronics, but it is also possbile to just do it manually. Write the current consumption on each plug, and only plug in upto 45A at any one time.

You can't trust end users to do this! I have caught our church Sunday
afternoon tea ladies with two 3kW kettles plugged into a fully wound up
four way extension cable running flat out. They melted its predecessor.

I now insist that all VH extension cables have thermal cutouts.

Actually this might be an application of the OWL current monitor alarm
feature which we have set on our VH so that at 90% of nominal rated load
it sounds a warning. The thing is mainly there to make sure people don't
leave it with the expensive immersion heater or fan heaters on.

There are other tricks too, such as switching 2 water heaters to half power when current budget runs out. Feed each via a diode so one gets +ve half cycles, the other -ve.

That *is* cunning.

If the sink heater is just 3kW those only add upto 10.5kW anyway, which is well within the abilities of a 45A feed.

Anyways, i've just been having a look at
http://www.screwfix.com/p/xq-lite-20...ght-240v/10988
Which is listed as a 20W device, but the Screwfix* details suggest fusing it at 16A. My OHMS,s law is a little rusty, but these two figures seem incompatible to me (it is a 240V device).
Do these things have a huge inrush current? or are Screwfix talking nonsense?

20w is 1/12th of an amp, and the usual available feeds will be fused at 5A, 10A and 13A, so a 16A fuse does seem a little weird.

Have a look at Thomann in case they have something more suitable for
your needs (we actually have the previous generation of these).

http://www.thomann.de/gb/stairville_..._4in1_rgbw.htm

More expensive than a plain vanilla white one but you have the option of
colour control and built in sound to light. Minor irritation is it will
come with European mains plug. Their white ones are overpriced.

--
Regards,
Martin Brown