Power supply

[Skimble]

Help! I've just become responsible for the oversight of premises issues at a community centre and have picked up an electrical project in between different phases of work. No-one who could have been helpful, e.g. the premises officer, was involved in commissioning the initial assessment and design for the rewiring and rationalisation of power distribution around the centre, and thus I find myself in an awkward situation as we pursue quotes for the second phase of work not quite knowing what we're asking for..! It's probably not quite that bad a situation, but it is beginning to feel that way, as I'm drip-fed correspondence from the past year and little bits of information that would have been really helpful to be in possession of before I started chasing contractors.

 

Anyway, the main point of this message. We need to upgrade our lighting provision in the community hall, which will mean running a three-phase supply from the MCCB to back stage to ensure we have amply supply to run everything we might add in the next 20-50 years. I'm not convinced that we have three-phase coming into the building. We have a grant to install new cabling and distribution boards within the centre, but not currently to have UKPN install a new three-phase supply. My question is whether or not it is possible to install a three-phase system in the building but run things on just one phase until we have raised the money/been awarded another grant to get the supply sorted.

 

I feel like an idiot asking that question, but it's the only solution I have been able to come up with to the current problem: we're time-limited in terms of putting the grant funds into action, but those funds must be used on the internal wiring and fittings. I can get the existing wiring and fixtures replaced on a like-for-like basis, but that won't give us any capacity to expand in the future, and that was part of the point of investing in the new design in the first place, or so I thought. Sadly, as I wasn't involved at that point in the process, and the person who was a) didn't know much and b) is no longer on the scene, I feel like I have a rock on one side and a hard place on the other. I'm sure someone out there will be able to help. :)

[dbuckley]

Maybe - sort of. But it is something you need to plan carefully for.

 

The fist issue is that loads that need a three phase supply wont work. So three phase motors etc are out.

 

The second issue is about neutral currents.

 

If one runs a three phase load off single phase, then the neutral currents accumulate rather than (sort of) cancel. A three phase installatioin normally assumes that there will be cancellation of neutral currents, so if one has a 63A three phase supply fully loaded, then the neutral current, in general will be less than 63A, and each phase current will be 63A. Run that 63A three phase installation of single phase, then the phase and neutral currents will be 189A.

 

On a smaller scale, a 16A three phase outlet to be safe would either need to be wired with a cable that supports a neutral current of 48A, or have the MCB downrated so that the maximum neutral current would be 16A, so replace the 16A three phase breaker with a 6A three phase breaker.

 

As you can see, it all gets ugly pretty quickly.

[Dmills]

Pull 4 core SWA of whatever size makes sense between the intake room and the stage, terminate in single phase connectors for now and when you get the three phase in you can replace the breakers and sockets with something suitable.

 

Whatever you do, oversize the conduit by at least 100%, it is worth it.

 

Also, I would be wary of going too far down the 'plan for 20 years' route, better to spend the money on infrastructure you can use now, while not closing off later possibilities then to spend on stuff which may well be unsuitable by the time it gets the extras to become usable (The regs do change).

 

Some things you may consider:

Hard power to all over the place in modest quantities (16A), LED is only going to become more commonplace and lots of older venues lack the ample hard power points required (particlarly in the grid).

 

CAT5/6 flood wiring, remarkably cost effective and you will find youself using it for everything from networks to POS to cameras to DMX to phones to cue lights (Seriously however much you put in you will wish you had more of it), pull FTP cable and connectors so you can also use them as mic lines....

 

House lighting or working lights upgrade, I am no huge fan of florries or LED but they are cheap to run as workers compared to the same amount of light from tungsten and many of these places spend at least as much time running Zumba groups as they do theatre, this can really help with revenue costs (Which are always harder to grant fund then capital)

 

Have a look at your emergency and safety lighting, T5 tubes are such a pain in the arse compared with the LED versions, and odds are good that some of it is time expired on battery packs anyway (Usually cheaper to replace the whole unit, expecially if it gets you away from endlessly swapping T5s).

 

Regards, Dan.

[Jivemaster]

Go to the hole in the floor where the power rises and look to see signs of three or single phase incomers

[Skimble]

Thank you for your quick replies - I knew I could count on the Blue Room crowd. :)

 

If I can't make it down to the hole in the floor myself I've got a contractor coming on Tuesday who will have to do that as part of the site visit, but at least I know that, messy as it could be, a decent electrician should be able to do something with this.

[Brian]

...a decent electrician should be able to do something with this.

 

Good luck in finding one of those who understands stage lighting and the like.

[paulears]

Do you have a member of staff who will be acting as the technical manager - as in the person all your visiting productions aim their questions at? This person would be the best one to get involved with this project.

 

The size and scope of the venue is critical. David mentioned 3 phase motors - and anything coming in that needs to lift things will want three phase. You also need to keep in mind that even small shows now want 3 phase. A rider this week for a quite small show asked for 63 single phase and 63 three phase - so not having it available will cause niggles. A look at your electricity meters will show you if you have a three phase supply - if it comes into the building, the meters are normally in the same place.

[top-cat]

anything coming in that needs to lift things will want three phase.

 

This isn't really true is it? There are plenty of single phase options available out there for hoists and winches.

[adam2]

If the electricity meter is readily accessible, then a simple inspection will determine if your supply is three phase or single phase.

 

A single phase meter will normally have FOUR thick cables connected to it, two from the power company, and two feeding the consumers equipment.

 

A three phase meter will have at least SEVEN connections, and often eight.

 

 

 

 

As regards extra or replacement wiring, it is a simple matter for your electrician to install cables etc. suited for either single phase or three phase. You could for example have a single phase 32 amp socket installed right now, that would supply about 6KW of lighting via suitable dimmer. Provided that the electrician installed two extra wires, not used at present, then when a three phase supply is available a 32 amp 3 phase socket could be installed instead giving about 20KW of lighting.

 

A three phase supply is preferred for large electric motors such as those found in elevators or large air conditioning plant.

 

Small motors and any common type of lighting or heating needs only single phase. If however the total load is likely to exceed about 24KW, then a three phase supply is likely to be required despite each lamp or other appliance being single phase. For example, a total lighting rig of 60KW could in theory be worked from a single phase 300 amp supply. In practice though the electricity company wont normally allow more than 100 amps single phase, 125 amps exceptionally. If that is not enough then a 3 phase supply is usually needed.

 

If you need to engage an electrician for this work, it would be preferable for them to be experienced in theatre work rather than just homes, offices or shops. Personal recommendation from another venue is probably the best bet, or recommendation via these forums.

 

 

 

[top-cat]

 

If you need to engage an electrician for this work, it would be preferable for them to be experienced in theatre work rather than just homes, offices or shops. Personal recommendation from another venue is probably the best bet, or recommendation via these forums.

 

 

Or just use an entertainment-field electrician or company??

 

Laurence from Backroom posts on here as "techsupport", he is a very experienced consultant for huge entertainment power and is really one of the most knowledgeable people in the business.

 

Hawthorns I know employ several qualified electricians who are used to theatrical and entertainment work. As, I'm pretty sure, do Stage.

 

All the big install companies should be able to help you as this is their bread and butter.

[Seano]

This isn't really true is it? There are plenty of single phase options available out there for hoists and winches.

 

And a world of tours not routinely carrying them. Paul is right: anyone touring through with motors will be wanting 3 phase. OK, maybe only 99% of them.

[top-cat]

This isn't really true is it? There are plenty of single phase options available out there for hoists and winches.

 

And a world of tours not routinely carrying them. Paul is right: anyone touring through with motors will be wanting 3 phase. OK, maybe only 99% of them.

 

Sorry just how many community centre tours do you know that tour rigging? I took it to mean events companies etc coming in, and just like every other venue in the UK which doesn't have 3 phase as long as this is communicated to the production company they should be able to supply single phase equipment or indeed just manual.

[Whiskers]

Is this what consultants are for?

[Andrew C]

Is this what consultants are for?

Not from my experience. "A consultant is someone who borrows your watch to tell you the time." My experiences up to now have been less than impressive.

[Junior8]

I think, with respect, the OP is starting at the wrong end. Any decent electrical installer can answer all his phase questions. The priority is to identify what of the present infrastructure needs replacing upgrading to make the space functional in the short to medium term. This will most likely be nearly like for like I would imagine. The you can start to guesstimate for the future. But how? Looking back to 1972 I couldn't see anything improving on the first mass market solid state controls which brought everyone, at least with a few quid, the two preset! My guess is that the future will see much more in the way of hard wired mains supplies to all parts with data feeds to match but much lower total loads. Energy is not going to get any cheaper which will increasingly be influential. I understand that student technicians are increasingly being asked to carry out green assessments as part of their training. So the focus will change from massive incomers to a dimmer room and traditional patching and IWBs. I'd agree with virtually everything said in post #3, indeed back in 1992 I had loads of draw-wires installed in the second part of a two compartment trunking system on a new school studio build for the reasons he outlines. Yet I and a colleague were treated with derision by a well known supplier for the number of audio tie-lines we specified which were seen as excessive. (The same firm also wanted to specify 5amp sockets on the IWBs as it was a school!) Thing was we started from what we wanted, asking for things like conduit to be bigger than strictly necessary as the labour was the main cost anyway. Start from the business end and work back...