Powering intelligent lights in a 16A ring

[Jamtastic3]

Hi BR,

Over the past few months, my venue has been getting more intelligent lights but I was just wondering how I work out how many intelligents I can power from the one 16A ring. It's no real problem at the momenet but this information would be very useful to know.

 

We have a mix of Clay Paky Miniscan HPE's, HES Technobeams and Robe DJScan 250XT's spread over 5 seperate 16A rings but I'd like to know how to allocate the power to them all more efficiant and safer.

 

Point to note about rig power - each ring has many 16A connection points but only leading to the one breaker per ring. I assume this means that each breaker can take up to 16A?

 

Cheers!

[Ben Langfeld]

Are you sure they're arranged in a ring? That doesn't really sound right.

[Jamtastic3]

Hmm... OK I'll explain the power supply part again.

 

The rig power in the ceiling is supplied by power from 5 breakers (there is another 2 but they provide power in another room). These are all on one main distribution box so I guess there is one main supply of power to these switches. If you switch on breaker one (marked 'ring one') then a sections of the power supply in the ceiling will come on. There is five sections of power tagged as 'rings'. Each section has around 5 to 8 16A female Ceeforms to plug into. I'm just wondering how many fixtures I can power to each of these sections from their power consumption ratings (amps/watts etc)

[niclights]

A 16A MCB means it can take 16A, yes. Of course the cabling both to and from this breaker must be adequate to support 16A too. This is not a huge amount though and 1.5mm2 is plenty for a spur or ring. Warmth on cables would indicate resistance and a problem here.

 

Beyond that it's all about knowing the max unit draw. Sometimes this is difficult to determine, for example the CP units only have a VA rating which requires knowing the power factor and this can vary greatly. Obviously you are within capacity at the moment or the trip would be going.

 

So long as there are no warm cables or trip failures there is no necessity to change layout. It might make sense to separate fixture types per circuit if you wanted the ability to isolate parts for particular events and save lamp life etc. Remember that the majority of discharge lamp based fixtures will take most power on strike. I find the easiest way to check loading is with a clamp meter. You do need to be able to clamp around just the live conductor and so must find a safe place to do this - if you have surface mount outlets then removing the cover and using here is often the best place. The disadvantage is they are not very accurate. If you have any hesitation about doing this sort of thing then don't.

 

This is probably in the wrong section :unsure:

 

/edit: It is also important to know the actual incoming supply. Is is not correct to assume that you have 5 (or 7) times 16A. There should be a fuse box/main breaker switch prior to bus-bar/distribution. The fuses here define your absolute limit.

[Pete McCrea]

If the breaker is at 16 Amps, then that is the maximum load per breaker. Current is found by dividing the Power in Watts by the voltage, which is nominally 230v ± a bit.

 

Example: 1000w Fixture. Therefore 1000/230=4.3A. So you could put 3 1000w fixtures on that one breaker, with just under 3 Amps left spare.

[Andrew C]

I'm just wondering how many fixtures I can power to each of these sections from their power consumption ratings (amps/watts etc)

Gawd knows! It is not normal for 16A circuits to be arranged in a ring, the design MAY be sound, but without more info, it is impossible to say.

[niclights]

@Little DJ: You cannot make such simple calculations with intelligent fixtures. There are huge inefficiencies with ballast along with fans/motors and other electronics. Generally, using the P=IV formula you will find the average moving fixture will require more than double the suggested draw based on lamp wattage alone.

 

You should also (ideally) allow a whole 10% tolerance on the 230v for UK.

[Trunker]

@Little DJ: You cannot make such simple calculations with intelligent fixtures. There are huge inefficiencies with ballast along with fans/motors and other electronics. Generally, using the P=IV formula you will find the average moving fixture will require more than double the suggested draw based on lamp wattage alone.

 

You should also (ideally) allow a whole 10% tolerance on the 230v for UK.

 

Also realising that some intelligent fixtures can take a 'surge' from the mains when they first power up.

[Pete McCrea]

Sorry if I wasn't clear, but I meant the total Wattage from the manufacturers specification, not the Lamp Wattage. Most Data plates on a fixture will have something along the lines of "230v 50Hz 1000w" as a Maximum draw for the unit. This would be the figure I use.

 

The other figure would be that stated on the manufacturers specification for Maximum draw. I would not advocate using the lamp wattage (unless as a simple generic lantern) for basing the calcs on. As stated above, a 575W Discharge lamp in a Mac 500 will draw less than the total 4.1Amps they state as maximum draw for the entire fixture.

[JimWebber]

...

Also realising that some intelligent fixtures can take a 'surge' from the mains when they first power up.

 

Although you will need to take surges into account, the problem may be minimised by striking the lamps in sequence. (I believe that many fixtures have a setting to delay the lamp strike, so they don't all go together)

[Jivemaster]

Ceeforms should be on individual radial individually breakered circuits. They should not be on a ring. The switch on surge can be three times the running current and MACs used (may still!) strike in order of DMX address setting

 

With the maplin power meter being on offer again this month (£15 rather than 26) and it having V, A, and powerfactor, it is an OK toy tho it has 13a connectors.

[The Yellow Transit]

Also realising that some intelligent fixtures can take a 'surge' from the mains when they first power up.

this is why you have B,C and D type brakers

[niclights]

In my experience striking lamps does not create instantaneous surges that require C or D type. I've never had any difficulty with B type - it is just something that should be allowed for on breaker value. On average I see approx 20% more power required on strike which will gradually reduce as lamp is stepped-up.

[Jamtastic3]

I'm at work today so I'll have a look at the power distribution box. I know there is a main power breaker in the back room (well 3 actually). One of these must feed power to the distribution box that has the 5 (+2) MCB's that I'm talking about.

 

Little DJ, you bring up good points about the MAC 500 power consumption because it states its max current draw on the fixture. This is the kind of informtaion I need about my fixtures to determine what kind of pull I'm getting at the moment from the power strike.

[niclights]

I strongly recommend actually measuring the load one way or another. I would not rely on stated values, certainly not if I were going close to the limits. If you do remember to allow for lower voltages :D