3pens Posted August 9, 2007 Share Posted August 9, 2007 Hello I have 48ways of dimming in my three phase venue (16 ways per phase). we have believed for many years that the feed to the dimmers (hardwired through the building so no ceeform or any kind of connectors) is 63amps. Does anyone know how I can find out exactly to put my mind at ease? There is no labelling to be seen anywhere! Cheers! Link to comment Share on other sites More sharing options...
Ynot Posted August 9, 2007 Share Posted August 9, 2007 Can you trace the cable back to the fuse board/breakers? They SHOULD be correctly labelled. A qualified sparks should be also able to tell you what guage the feed cable is and whether it is sufficient to carry up to 63A (or more), assuming your breakers are rated for 63A 3-ph. Link to comment Share on other sites More sharing options...
3pens Posted August 9, 2007 Author Share Posted August 9, 2007 Can you trace the cable back to the fuse board/breakers? They SHOULD be correctly labelled. A qualified sparks should be also able to tell you what guage the feed cable is and whether it is sufficient to carry up to 63A (or more), assuming your breakers are rated for 63A 3-ph. That is not labelled but I went down to the intake room of the pub beneath us and that is labelled correctly. Many thanks! I am going to get labelling. cheers! Link to comment Share on other sites More sharing options...
SteveAATW Posted August 9, 2007 Share Posted August 9, 2007 Cable should be 16mm minimum for 63A, may need to be 25mm under some circumstances. Link to comment Share on other sites More sharing options...
DavidLee Posted August 9, 2007 Share Posted August 9, 2007 Can you trace the cable back to the fuse board/breakers?That is not labelled but I went down to the intake room of the pub beneath us and that is labelled correctly. Many thanks! I am going to get labelling.I'm sure that you did, but make sure you trace back all the way to the company fuses. Our village hall wiring is rated at 100A but we were alarmed to find an 80Amp fused breaker between the 100A company fuse and the consumer units! The rating isn't obvious until you open it up (or in our case bump into the hall's electrician doing his annual safety check). David Link to comment Share on other sites More sharing options...
niclights Posted August 9, 2007 Share Posted August 9, 2007 I was essentially going to say the same thing - don't go by labels but open and look at fuses on main breakers. Link to comment Share on other sites More sharing options...
Roderick Posted August 9, 2007 Share Posted August 9, 2007 I have 48ways of dimming in my three phase venue (16 ways per phase). we have believed for many years that the feed to the dimmers (hardwired through the building so no ceeform or any kind of connectors) is 63amps.Isn't 63A a bit light on for 48 channels?Assuming they are 2kW dimmers you would need 10A per channel = 480A split over three phases makes 160A.......Also, it appears that you don't have any breakers or fuses within your venue which could be problematic if you overload the supply, you may not always have access to the pubs' intake room. Maybe consider having breakers installed at the dimmer racks. Link to comment Share on other sites More sharing options...
niclights Posted August 9, 2007 Share Posted August 9, 2007 That sort of thinking assumes not only that you load each channel at 2kW but also that you put them all on full at once. Reality is likely this never happens. I do agree that if there is no additional protection before fuses then there should be, esp. given the potential to easily exceed supply. Link to comment Share on other sites More sharing options...
SteveAATW Posted August 9, 2007 Share Posted August 9, 2007 You say the dimmer is hardwired into the supply - is there not even an isolator switch next to it? If not then to comply with the regs there should really be an isolator adjacent to installed plant and machinery, if the over current protection is not local either then it would be a good idea to combine the two and put an isolator and MCB next to the dimmer. Link to comment Share on other sites More sharing options...
Roderick Posted August 10, 2007 Share Posted August 10, 2007 That sort of thinking assumes not only that you load each channel at 2kW but also that you put them all on full at once. Reality is likely this never happens.You are absolutely right, 160A on each phase is very unlikely but I still think 63A is very light on. I normally use 60% of the capacity to work out 'reasonable' supply, mostly when dealing with generators or temporary connections. In my calculation that would still make it 96A/phase.There are two scenarios where this capacity could be easily reached:1- Unbalanced load - a specific state could end up using all dimmers on 1 phase, even if your plan has all the loads nicely spread2- Cross fade - if you have a change between two large states each bordering on the maximum capacity This obviously hasn't happened in the past few years or the OP would have found out where the fuses are a lot earlier, but if they are looking at the situation at the moment it is something that could be taken into consideration. Link to comment Share on other sites More sharing options...
niclights Posted August 10, 2007 Share Posted August 10, 2007 Agreed on all counts. But maybe this is drifting away from original question so think will leave it there! Link to comment Share on other sites More sharing options...
adamharman Posted August 10, 2007 Share Posted August 10, 2007 Cable should be 16mm minimum for 63A, may need to be 25mm under some circumstances. That depends on the type of cable and the length of the run. I agree 16mm2 is preferable as it will run cooler, but 10mm2 XPLE SWA is good for 70+ amps. Volt drop is 4mV/m/A so no problem with volt drop unless it's a longish run (>35m). http://www.batt.co.uk/images/pics/57124e4a.pdf - source of those figures If it is SWA, most manufacturers mark on the outer sheath what size it is. Link to comment Share on other sites More sharing options...
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