12v wired lighting

[bexxxxx]

Newby here - be kind, knowledge is poor

I am trying to buy the components for a 12v wire lighting system to be strung between two beams. My sparky has put in wire from the beam to a cupboard below (approx 4 meters away) for the remote mounted transformer.

I have been looking at 300va transformers and am getting very confused - I need one which is dimmable.

Would this be ok? JCC Toroidal Transformer 1x300VA single way output (JC4010)? I want a great quality transformer that won't blow up if I dim it, I am not even sure if the JCC one is the right sort!

Please help!

 

[MalcofArabia]

would these be of help ?

http://www.ecoledlight.co.uk/ShowDetails.asp?id=410

Bit expensive though

 

[bexxxxx]

looks good thanks!

I don't really know what I am looking for (would the above be any good) .............

help

 

[RossR]

You also need to make sure that the dimmer is suitable for dimming your transformer. There are different types (trailing and leading edge) and most dimmers have to be de-rated if driving an inductive load.

Why don't you get your spark to help you?

 

[bexxxxx]

lol - sparky help me - you are funny.
The best I get from my sparky is a scowl these days!

Bl*%£y nightmare he is!

He was supposed to put 6mm wire in for the 300va transformer and has only put in 4mm and now the roofs gone back on and I can't change it without taking the roof off!

The dimming is being done by a mode automated lighting system being put in by a third party (ie. not my sparky) and so my sparky gets all grumpy when I speak to him about anything!

Basically i have a sparky, a mode lighting engineer and neither of them apparently can help - as they both say it depends on the other, all I want to do is buy my light fittings so I can move back into my house!

Think ill just go down the pub and use their lights.........

 

[RossR]

How do you intend to show compliance with Part P of the building regulations?

 

[RossR]

Your problem seems to be that neither your "spark" or your "lighting engineer" are taking responsibility for the design of the installation. It seems that you are taking on the role of designer. That's a problem for two reasons:

1. You aren't sure what you are doing.
2. You can't get someone else to certify the work as compliant with building regs. (unless you have notified the LABC in advance and paid there silly fees.)

It sounds as if this advice is too late but what you should have done is paid a single person/company, registered with a self certification scheme, to do all of the work and certify it.

 

[bexxxxx]

My sparky is signing off the work for building regs - I am just purchasing the light fittings for him to fit.

Didn't realise it would be such a big deal

 

[ericmark]

There are three ways to supply 12v for lighting.
1) Transformer - These have a high inrush and often blow any dimmer switch used.
2) Inverter - These as already said are split into two types leading and lagging. Some will work with dimmer switches however they need to be matched and really only way is to buy lamps, inverter, and dimmer all the same make and designed to go together.

The inverter is a special device which converts the AC to DC then back into AC at a high frequency and then transforms it down to 12v and samples the voltage and corrects it to keep it spot on the correct voltage. They are designed for the quartz halogen lamp which depends on the quartz envelope being kept at the right temperature to reflect the active material back onto the tungsten element. It is this careful control of the voltage which makes the lamps last longer and run brighter than the low voltage (230v) GU10 types. Once one adds a dimming switch one destroys this balance. So if using a dimmer one may as well save a lot of money and use the low voltage type instead of extra low voltage. Then also you have removed the problem in matching all components.

 

[ban-all-sheds]

He was supposed to put 6mm wire in for the 300va transformer

Why?

Basically i have a sparky, a mode lighting engineer and neither of them apparently can help - as they both say it depends on the other,

It's the project manager's job to resolve problems like that - you should give him a kicking.

 

[electronicsuk]

He was supposed to put 6mm wire in for the 300va transformer

Why?

To keep volt drop in check? After all, there could be up to 25A on the ELV side, and there's the 4m of supply cable plus however long the suspension cables are.

 

[ban-all-sheds]

Ah - I assumed it was he LV side he was talking about - sorry.

 

[JRK]

Hello, Just been forwarded information from our technical team. Can I declare an interest here.... I am from Mode Lighting.

I am not aware of any enquiry to our office regarding the problem so if you can mail me and let me know who is supplying the equipment, which system it is and which engineer you have been speaking to I will follow up with them but to add some information on transformers and wire systems:-

A tension wire system uses two conductors seperated by a distance (usually around 100 - 120mm) which lamps are connected to for the lighting. An electronic transformer is not suitable for these type of systems as the output from an electronic transformer is high frequency which results in the conductors acting as large radio antenna which causes radio interference and will result in the protection in the transformer shutting down.

This causes an immediate problem as electronic transformers are usually lighter, more efficient, quieter when dimmed and easier to dim but unsuitable for this application where a wirewound transformer will need to be used.

The cable size is important due to volt drop and current loading. One option would be to use higher efficiency LV lamps where a 35w IRC (infrared coated) lamp gives the same output as a standard 50w lamp (20w IRC = 35w standard). This would provide a lower load = lower current = less consumption.

As for the correct transformer to use, a standard wirewound / torodial transformer of the right rating would be OK but you need to make sure it can be dimmed. Many high power transformers have a filter or PFC circuit installed which will fail if you try to dim it.

A standard wirewound or torodial transformer is an inductive load and would require a dimmer that dims based on the leading edge part of the mains cycle.

Another option is a company called Multiload who manufacture an intelligent transformer which is controlled by control signal ie not mains dimmed and has built in regulation control. Whether this is suitable would depend on the which Mode dimming system you are using and the location of the transformer in relation to the dimming equipment.

I've just searched for the transformer you listed and found this comment "240V - 12V Toroidal transformers with internal current protection, surge suppression, auto-reset thermal trip. Dimmable with inductive dimmers"

So from a dimmer compatibility pov it will depend on which dimmer / system is being used however the cable / load issue would still need to be resolved. It may be possible to change the output fuse on the transformer to a lower rating or use a smaller transformer if you change the lamps to lower ratings to prevent overloading of the cable but this is best checked with the Electrician and the transformer manufacturer.

Apologies for such a long post. Hope it helps.

J.