Radio 1 roadshow trailer

[mhar]

Last week I was asked by an extremely good (but impulsive!) customer if I could give a hand today and tomorrow helping a sound engineer sort out the new led dmx lighting on the ex radio 1 roadshow trailer. I met with my customer yesterday who told me my brief was to make it ‘right’. I started this morning.
The trailer is basically a 40’ metal artic trailer. It is used for private hire and for new years eve on Bideford Quay (which is a massive and renowned event). Prior to starting I consulted 713? in the bgb (which I have unfortunately left on the trailer).
The power requirements are not great, a 16.5kW sound system drawing around 12-15A on start up plus a few amps for the lighting. They have an onboard commando socket which they plug into any available 32A supply or they will use a generator if no supply is available. They have been relying on the supply point earth or a rod with 6mm earthing conductor when generating. There is no rcd protection.
Whilst waiting for my customer to appear to advise that the supply and earthing arrangements needed addressing and that rcd protection was required (certainly for new), myself and the sound engineer busied ourselves. Late this afternoon we were told that my customer died this morning and could we just go ahead and do whatever is necessary. I feel a bit ‘on my own’ and would appreciate any pointers or advice on my following thoughts:-

Earthing has to be tt as not under supervision. I therefore disconnect earth on commando socket (1m away from cu) or after isolator (.5m away from cu). What labelling would be required on cu?
Bonding. Chassis bonded in 10mm. Two sets of removable metal steps require bonding back to met when in use, separate bonding conductor to each with a ring crimped on end and provide earth stud on each set of steps (steps stowed whilst not in use). Assume I cannot supply an earth stud on the chassis and earth the steps back to that.
RCBO’s throughout.
Lighting is controlled by a dmx controller, each light has it’s own mains feed but linked via dmx patch leads. Sound engineer would like the effects lights to be on two different circuits and the dmx controller on a third to minimise results of any tripping. Instinctively I think this is wrong but not sure why.

Anything else I need to be aware of?
I will do my best to respond to any points requiring clarification but may have to go out this eve
Many thanks

 

[overskilled]

The trailer should have a commando male on it and the connection lead have a commando female on it so you don't end up with exposed live pins? (i.e. lead with 2 male plugs on it)

 

[Marvo]

Late this afternoon we were told that my customer died this morning and could we just go ahead and do whatever is necessary.

You're highly unlikely to get paid if there's no customer (or a dead customer)......

 

[mhar]

Thank you overskilled. Current socket is broken and will make sure it is replaced as you advise.
Marvo, Not an issue but thank you for caring!!

 

[Marvo]

Dead customers are notoriously late payers....

 

[Rockingit]

OK.... assuming that you're satisfied with the business end of the arrangement, the tech is relatively simple.

For starters, this isn't covered by the BGB, there's a separate BS standard.
2) Earthing - in theory TNCS is a bad idea, less so TN-S, and TT is ideal but your chances of getting a robust earth in a temp install environment are slim. Get a 'bad' earth and the sound engineer won't thank you for it. If you can get a feed from a TN-S origin I'd be quite happy to use it (assumes that the trailer chassis has been bonded).
3) If you want to be purist then you keep a phase clean for audio and keep a separate 'clean' earth too, but again I wouldn't waste too much time on it.
4) RCBO's are good as especially this time of the year you'll have leakage all over the place due to damp air. (Especially if you've got cheap Chinese lights!!!)
5) Lights on different phases to control is of no consequence whatsoever as the control path is S-Extra extra extra low voltage digital.
6) TBH, if there is no dimming involved (so ALL led) then you don't even really need to worry about keeping a clean audio feed, just make sure it's all balanced across phases.

7) get massively stuck then by all means PM me for my number - welcome to the world of has-been rock and roll and wanna-be starlets!

 

[mhar]

Thanks for the reply.
Business end propose using a seperating transformer. Single phase, load should be 20A max.
re point 5, traced earth path through lamps, it is only the can that is earthed so I am now not worried about the sound guys request but many thanks for your additional info - best to be doubly sure!
Chassis and steps bonding was non existent. It is a while since I had to calculate the size of a bonding conductor but I propose using the 10mm fine stranded rubberised stuff (HO5 / HO7V-K). Doubtless my sizing is overkill but the steps bonding (two sets) will be disconnected during transport so this cable will be subjected to a reasonable amount of attaching / unattaching therefore my sizing is related to the environment rather than electrical requirements. I will crimp a ring on the end to enable ease of use and will place a warning on the cu that it must not be energised until the steps bonding is in place. Agree?
Re point 7 - been there for a few years already, many thanks for the offer of contact but I think I have now unoverthought my original ideas and I feel happy but still welcome any comments

 

[Rockingit]

It's only the Ali of the cans that get's earthed, that's standard.