Betapack3. 3phase 1phase safety

[andy wood]

Just become the proud (2nd) owner of 3 newish betapack3 to replace old analogue strand tempus. So bringing everything up to scratch

 

First, I do know that all elecricity can kill, and 3 phase does it more efficiently, but...

 

Quite a few text books and guides (recent 2010). Recommend separating phases into foh, flies, stage etc and to avoid mixing phases through patching or on bars etc and a six foot 2m rule on socket separation. Now the betapack can be on a 3 phase supply and it looks like this is split so each phase supplies 2 channels , so you have mixed phase in the box.

 

our three will be single phase supply , but split two on one phase, one on another ( all as yet unidentified) but it is likely that some x-patching will occur. Now , rcd, mcb protection has come a long way , so is there anything practical or legal to be worried about, other than labelling for 400v . Current ABTT guides seems a bit hazy on this area

 

What do people do, or think ?

[kgallen]

The 2m separation rule disappeared from the IEE Wiring Regulations many years ago... because as you've found, it's wholly impractical. To get a cross-phase shock, you need to have two fixtures with phase-to-earth faults where the protective device hasn't cleared either fault.

 

That said, if you can partition fixtures to keep some separation, then why not. However, in practice you might find that tricky with anything but the smallest and simplest of rigs...

 

Disappointingly the HSE have this "rule" in one of their guidance notes (*1) about not mixing phases on a given lighting bar.

 

What is advisable though, is yellow 400V warning labels in proximity to socket outlets that can be on different phases. BS7671:2008 514.10.1, along the lines of these: http://www.labelsonline.co.uk/danger-400-volts-labels-50x25mm-el1068?gclid=CjwKEAjwsLTJBRCvibaW9bGLtUESJAC4wKw18TxVeYcyu5_hyOFPdPbeHzCD2b8Zn0M5TsjBDrDKdRoCw4Tw_wcB

 

Blue Room have covered this topic many times. If you have a login, you should be able to see the "Safety" forum and this discussion: http://www.blue-room.org.uk/index.php?showtopic=15328

 

However, I'm just "a bloke on the net" so make your own enquiries... (*2)

 

(*1) GS50 says: "22 Great care is needed if the equipment is to be supplied from a three-phase supply or if adjacent items are fed from different phases. Many local authorities have their own rules on this topic. They should be consulted.". However disappointingly, the section on "Lighting Systems" still says "Only a single phase should be supplied to any one boom and the connections from the individual light fitting to the boom should be by plug and socket."

 

(*2) You could Google HSE, IET, Blue Room for example.

[Edward]

I agree with all Kevin has said above.

 

Many people will say keep phases seperate, however you couldn't get phases much closer than in 3-phase cable which is just as likely to have a fault as 2 lanterns being fed from different phases, so it's a little pointless on a modern RCD protected system!

 

Also, many large 3-phase dimmers with multi-pin outputs (Socapex) will be wired channels 1 to 6 phases 123123, or 112233, so again it is expected you'll have multiple phases on a bar.

 

Of course when you can and it is reasonably practicable, then it is best practice to seperate out each bar.

 

For your scenario I'd probably put one phase Betapack for FOH, and the other pair of Betapacks on another phase for over stage bars. As long as the electrical installation is RCD protected and regularly tested you're fine.

 

Edward

[andy wood]

 

You have confirmed what Ive been thinking through. We need to get the protection and the labelling upto standard.

Im ditching all the dodgy extensions as well and have put in socapex bars, and spiders.

The dimmer packs have BS4343 sockets , and we are swapping out 5a for 15a BS546 plugs on the lanterns.

With Fuse, MCB and RCD protection we should be OK

 

Many thanks

[kgallen]

Im ditching all the dodgy extensions

 

Ditch or repair the dodgy ones, but there will often be a need for some extensions unless you really do have socket outlets everywhere. If nothing else, it can be worth making up some 1m or 2m 15A extensions from good sections of your old cables, so lanterns can be rigged in exactly the right place, the cable looped nicely to the bar and secured, then using a short extension if needed to get to the socket outlet.

 

Kevin

[andy wood]

Hi Kevin,

 

Thanks,

Fortunately the stage is not too big at 10m x 8m , so with a good supply of IWB bars we shouldnt need many. Part of the move to 15a is to use H07 flexible for all lighting extensions , so its going to get pricey. Im also trying to reduce the PAT load as this has to be done independently ( I dont do my own sfuff - its marking your own homework) so aiming for just enough and no more.

Having seen extensions (mis)used in so many imaginative ways in even 'professional' events the fewer the better.

With socapex at least you only have one, not six, and its heavy enough to recognise that it needs the correct support.

 

Were using the moulded plug/socket orange 'garden' extensions for 13a mains and will just ditch them if they fail PAT

[kgallen]

I dont do my own sfuff - its marking your own homework

 

Oh I'd argue the contrary! I'd much rather do inspection and test on the equipment I'm using, then I really do know it's safe to my (high) standards and I can fault find and repair it when it's not. Have you got a PAT tech you really trust to do the job properly for the equipment you have? i.e. not one of the green-sticker brigade who will be confused if it doesn't look like a kettle with a moulded 13A plug on it? Who is assessing the inspection and test regime and frequency? You're not necessarily in the one-year-fits-all camp (not that there is such a thing in the IET Inspection and Test CoP (*1) ) despite what your "PAT guy" might tell you.

 

You should be doing ongoing user-inspection-on-use anyway... this is going to detect most issues.

 

Fixed install inspection and test is another matter when you do need a sparks with the correct kit and knowledge.

 

(*1) http://electrical.theiet.org/books/inspection-test/in-service-inspection-4th-ed.cfm

...to be used with appropriate training, knowledge and experience of course...

[andy wood]

Hi, sorry just being flippant !

Of course we inspect and test everything while in maintenance and before use. Always best to test on the floor before you hang and patch. Also you can cover the mechanical aspects that PAT doesnt touch

One of the benefits of independent PAT done properly is a second wise pair of eyes. Its a matter of finding the right expertise with the right kit...the 13a brigade...hmmm. But some stage services companies offer good support here especially with installation inspections

 

I agree with you on the one-year fits all but its often required by liability / property insurance and management...but for amateur theatre, say 25 days / 100 hours a year...with effectively permanently mounted FOH only check when the lamp goes, and other lanterns set and struck each performance. Thats when effective true risk assessment comes in

 

But we are a little off topic. Perhaps its a good one for the general discussion thread ?

[kgallen]

Hi Andy,

 

I agree we're off topic - but hopefully your original question has been addressed - unless someone else wants to join in with new information of course!

 

Regarding the frequency of inspection of test I was more thinking your circumstances might warrant a 3 monthly or 6 monthly regime if your equipment gets heavy use or is moved frequently. However I think I'm preaching to the converted as it's clear from your previous post that you're well aware of these things and on top of managing your equipment maintenance regime. I'm glad you have found a competent inspection/tester - I'd agree the second pair of knowledgeable eyes is worthwhile!

 

Kevin

[andy wood]

Hi Kevin,

 

Yes thankyou I think we now have a better handle on the 3 phase issues, so we can discuss meaningfully with the hall management and the electrical contractors ( if your not careful they just want to strip and replace everything back to the street, and we dont have the budget for that) . I've now worked out that a stage lighting 30amp ring main is most likely fed from the 3rd phase so all are present and in reasonably close proximity, so its been worth the time and effort to explore what is current practice. At least with the betapack 3 and some good protection we should be in a much better place than we were....

 

Now to downrate the betapacks for 30amp use....but thats for another post!

 

Andy

[kgallen]

Now to downrate the betapacks for 30amp use....but thats for another post!

 

Well that's easy enough, you fit the phase combiner bar internally and wire the Betapack with a 32A CEEFORM and some 6mm TRS. Then get yourself a number of 32A CEEFORM outlets fitted to a dedicated final circuit with 32A MCB and 30mA RCD.

 

You then have to keep your total dimmed power consumption below 8kW!

 

...assuming that was the essence of your next question!

[iank99]

The main concern over the last few years seems to have been that labelling is profuse, simple and meaningful so that folks using the rig are aware it's 3 phase and probably of mixed code with conductor colours (of course - try explaining 3 phase to an english teacher in a 6th form college).

 

At that point (the reasoning seems to be) your obligation as a "venue" is discharged along with the fact that only "suitably skilled" people are permitted to do complicated stuff like plugging in extension cables and that the installation is essentially safe to use.

 

The old wiring regs which placed the emphasis on separation appear to come from a time when it acknowledged that some numpty would come along one day and try to kill himself by electricity whereas nowadays they might read your labelling and decide not to bother.

 

Personally, it's still at the back of my mind to design separation in to rigs - stuff does happen to the best of us and the second corollary to Murhpy's Law says that it will be that me it happens to most likely.

 

You can design a lot of "stupid" out of your installation that labelling won't correct - just have in the back of your mind that it might not be you or one of the 'experienced' folk trying to use the kit.

[andy wood]

Hi Ian,

 

Thanks for this...thats my prime concern. A lot of this kit is in schools, halls, and used by enthusiastic amateurs. I want to be sure Ive done all I can to build a safe environment and practice. It now occurs to me that with a 3 phase betapack used with socapex you will have 3 phase in the multicore. It better be 500v rated , and tested at that voltage for PAT.

 

Andy

[andy wood]

Well that's easy enough, you fit the phase combiner bar internally and wire the Betapack with a 32A CEEFORM and some 6mm TRS. Then get yourself a number of 32A CEEFORM outlets fitted to a dedicated final circuit with 32A MCB and 30mA RCD.

 

You then have to keep your total dimmed power consumption below 8kW!

 

...assuming that was the essence of your next question!

Hi,

Yup already done the easy bits recabling and a new plug. I also changed the cable gland . But for safety I am planning on replacing to C10 MCB with C6 of the same make. Its the channel diversity, not the power, that needed. The 32a sockets are already there but not great. Looking at better protectin via mcb/rcd at 32A and maybe a fused isolator too....

[kgallen]

But for safety I am planning on replacing to C10 MCB with C6 of the same make.

 

I'm not sure I'd do that. What if you need a 2kW channel for a sun keylight for example? You've got 32A per Betapack, which is a very common configuration in amateur venues, can you not allow the user to handle the diversity? 6A is a little bit close for pairing two 650W lanterns on one channel which I would expect to be a common requirement.

 

You say "for safety" but I'm not sure how safety is helped much. A human can be killed by 30mA - the difference between 6A or 10A is a bit irrelevant in this respect. The only reason to derate to 6A would be if you've got say 0.75mm2 cabling rather than 1.25mm2/1.5mm2. 6A versus 10A is an overcurrent/overload limit which relates more to fire risk than human death risk.

[andy wood]

can you not allow the user to handle the diversity?

 

Unsupervised,? No...

[kgallen]

Hi Andy,

 

One last thing before I back out on the MCB idea, because I think you need to read the specs on the MCBs before you convince yourself the swap-out it going to achieve what you want.

 

BS7671:2008 Fig 3.5 Type C circuit breaker to BS EN 60898

 

A 6A breaker will carry 8.5A indefinitely and 10A for at least 600 seconds (10 minutes).

A 32A breaker will carry 45A indefinitely and 60A for 200 seconds (say 3.5 minutes).

 

If you downgrade the channel breakers to 6A, and your unsupervised users overload each channel to 10A, then your whole-pack 32A breaker will likely fire long before any channel breaker does.

 

Fig 3.4 Type B breakers have the same response times for these examples.

 

I just don't want you to think that 6x6A breakers are going to keep you within the 32A pack breaker limit. 6x6A breakers are going to tolerate at least 6x8.5A forever. That combined 51A will be tolerated by a 32A breaker for 900 seconds (15minutes).

 

...but I am just a bloke on the web.

 

Regards,

Kevin