Paralleling cables

[mike-b]

Is this a big no no (I suspect it might be)?

Here is the situation (this is for stage lighting, so not a domestic building):

We have a 63A isolator going to a consumer unit (I presume with a 63A main switch, I didn't make a note of it). From here we have a 20A MCB wired to 12 fused switches (all with 13A fuses at present). From each switch we have 2.5mm twin+earth cables running about 15m, partly in conduit, partly in free air. These cables are then connected (not sure by what method) to a pair of 18 multicore cable (approx 20mm outer dia, guess it's either 1mm, 1.5mm or 2.5mm cores) - so each multicore has L,N,E from each switch (i.e. 6 circuits on each). This runs for about 5m before breaking out into individual 1.5mm pvc flex.

What we would ideally like is to have a single 42A supply where the multicore breaks out. Clearly this isn't going to be possible using the existing cable. But would it be possible to pair up some of the 2.5mm twin+earth, then multicore circuits to get a single supply higher than the existing 13A? 26A to 30A would be nice. So we'd bypass the switches, connect two lots of 2.5mm to a new mcb, and then at the other end connect the corresponding 2x L & 2x N to form a single supply.

Is this an allowable configuration, even if not typically reccomended? If so, what would be a max current we could get from this supply? Going even further, could we parallel up 3 lots of cable to get even more current carrying capacity?

 

[wattsup]

Typically, a lighting( pro rig) will have 1x 50/63a supply so easy to plug in to an already installed, linked together... 63amp supply. That is the norm. Sometimes bands have several lighting rigs which are linked using 13a plugs, so usually relying on a 32amp ring main breaker. The host's breaker may trip as it should. Many bands make up there own lighting rigs, often times over the capacity of the protection. There is no way round this, unless the host provides a 63amp connection.

Many times stage 'disruption' is because of over current demand....even some pros think they can plug into the mains via a 13a socket, and then wonder why all the lights have gone off....stage lighting is hungry

 

[mike-b]

Thanks for your reply. I'm still not sure if I can parallel up multiple twin + earth cables? This is for a semi permanent installation - we don't have to worry about bands bringing their own lighting rigs.