Low Voltage Bathroom Lighting

[CliveDiy]

I intend to fit six IP65 12V light fittings in my bathroom, the wattage of each lamp will be 50W.

Could anyone advise on what size transformer I will need to drive them, or will each lamp need to be on it’s own transformer, also what size cable will I require on the low voltage side and what would be the maximum cable run from the transformer to any one lamp.

I intend to take the supply via a fused spur off an existing lighting circuit.

Thank you to anyone who can help.

 

[Steve]

fused spur not needed. wire them where the bathroom light used to be

300w in your bathroom? you thought this through carefully?

i would fit 6 transformers, each rated at 60VA, one for each lamp, use normal lighting cable to join to the lights.

if you fit one transformer, it should be rated at least 300VA, preferably 400-500VA (will last longer) and pay extra for a good brand.

if you do just fit one transformer: 300watts / 12volts is 25 amps . Use 4mm² cable between the single transformer and each light.

 

[ban-all-sheds]

what size cable will I require on the low voltage side and what would be the maximum cable run from the transformer to any one lamp.

http://www.tlc-direct.co.uk/Technical/Lighting/VoltageDrop.html


Also, are you aware that this work is notifiable?

 

[CliveDiy]

Hi Ban

Thank you for your reply, I am doing a complete house re-wire, and yes I do know the work is notifiable, well at least if I don’t want problems should I wish to re-sell the house.

But yes I shall have all the work checked after the first and second fix by an electrician registered with the ECA, I must have that little bit of paper work.

 

[ban-all-sheds]

I am doing a complete house re-wire

All DIY, or under the design authority, direction & supervision of your electrician?

But yes I shall have all the work checked after the first and second fix by an electrician registered with the ECA, I must have that little bit of paper work.

Have you found an electrician happy to do this, and checked with your LABC that they are happy?

 

[CliveDiy]

Hi Crafty

Thank you very much for your reply, I must admit I do need educating, you see I have never fitted low voltage lights before.

All I have ever put in a bathroom is one central ceiling light usually 100 watts, 240v because I do like a good light.

I have seen these LV down lights in show homes and thought I would ring the changes, I don’t want any dark areas in the room and I know the lit area from these LV lights is smaller.

I don’t want to get a sun tan from them though LOL, and I don’t mind you putting me right in the least.
The bathroom is 10ft x 9ft, how many lamps and what wattage do you think would do the job.

If you have a look at Wickes Good Idea Leaflet 89 on their website at diagram C, it shows the wiring coming off a junction box or existing ceiling rose then through a fused connection of 3 amps to a 4 terminal junction box and then onto a switch.

Tell me if I’m wrong but I was thinking maybe I could simply run a feed into fused spur then from there to the transformer and onto the light fittings.
I am thinking they are wired the same as conventional lighting, you know daisy chain.
If you don’t mind sending me a sketch of how it should be wired I’d be most grateful.

Can I ask you, if you know, is it ok to run the feeds for any lighting circiut in the house from light switch to light switch, instead of ceiling rose to ceiling rose, in other words all that would be going to each ceiling light would be a switched live and neutral plus the earth of course. The type of ceiling lights I shall be fitting are the brushed steel ones and I'm not sure if they have provision for a loop in system, and I have seen the neutral wires connected with a nylon connector in the switches, it doesn't say much in the regs about where the feeds should be looped.

Hope you don’t mind me asking but are you a sparky by any chance or do you just get your girlfriend or wife to read the wiring regulations gently to you in bed at night.
Nah you must be the former and thanks once again for your help.

 

[Steve]

lights can be looped at switches - neutrals are always kept in nylon connectors as you say, never connected to a light switch - BANG. Lets not go there. Looping at switches is growing in popularity nowadays due to people wanting non-ceiling rose type fittings, and junction boxes are frowned upon as they are often inaccessible.

For that room, i would have 5 or 6 lights, but make them 20w. Softer light, will feel less clinical. Throw the Bad Ideas leaflet in the bin. You see the cable that supplied you old ceiling light, use this to supply the transformer(s).

I'm not a sparky, but i know a lot about electrics and I am considering getting formal training and making a career out of it.

 

[CliveDiy]

Hi Ban

I have managed to find someone prepared to check the work, always of course providing he will still do it when the time comes, I guess its just a chance I will have to take, however it’s strange how the local building control can send their inspectors out to check building work but don’t want to know when it comes to wiring, all they are interested in is the certificate, but I still have to pay them a fee.

I would like to know what I shall be getting from them for my money as I have had to phone around myself to find an electrician to check the work.

It’s only my view of course but I do think it would be a good idea if part of their fee included them supplying a register of electricians prepared to do checking.

 

[Steve]

You pay LABC to check your electrics. same as they inspect building work, they inspect your electrics and test it.

If they are saying you need to get another spark to test it and pay for this seperate, tell them to put it in writing, this is WRONG.

Then tell them your going to do the work anyway, pay them their fee telling them you want them to send a spark to come and test it, and if they dont send one its their funeral.

If you ever run into trouble with the law re. the legality of the electrics without a cert, show the letter they sent re. them not testing it.

 

[CliveDiy]

Thanks Crafty

Just letting you know, I'd like to ask you a bit more about the lighting wiring tomorrow.

All the best for now Clive

 

[PompeySparks]

Crafty, I read these forums fairly regularly (don't say much though!) and have to say i'm surprised you are not (yet) an electrician!. Your advice is very good - you'd do well in the trade!

 

[ban-all-sheds]

I would like to know what I shall be getting from them for my money as I have had to phone around myself to find an electrician to check the work.

The most recent version of my summary has details of the ODPMs view that LABCs are not allowed to make you provide your own electrical cert.

 

[CliveDiy]

Hi Crafty

As I said to ban all sheds earlier 27/01/06, the whole house needs rewiring, I had an electrical report done on it before purchase.

I won’t go into to much detail about it, but there were things like the water heater on the same circuit as the outside lights, no earth in some of the upstairs lights, apart from fridge freezer, running off 1.5mm cable, the list went on, so I will not be using the old cable which fed the existing ceiling light but a new feed which will be in the switch, as I said the loop ins will be from switch to switch because of the type of ceiling lights that will be fitted throughout the house.

You seemed to indicate that I would not need to use a fuse as shown in Wickes Guide, correct me if I’m wrong normally I would run a lighting circuit in 1.5mm cable usually to supply 10-100watt lamps and protect the circuit with a 6 amp mcb.

Can I simply tot up the total wattage of the six 20 watt LV lamps giving me 120 plus lamps in other upstairs rooms to give about 1000 watts in total and bung the whole lot on the 6 amp mcb, if so have you any idea why Wickes are going on about putting the supply to the transformer though a 3 amp fuse, as I said at the onset I haven’t done anything on low voltage and thought maybe the transformer needed protecting by a lower rated fuse than the rest of the lighting circuit.

All this talk about LV down lighters in the bathroom I’m still wondering which is the best way to go, LV or mains down lighters, the reason I say this is because half the bathroom ceiling is a flat roof and I’m thinking if the maximum cable run will enable me to get the transformer/s back into the main loft area of the house.
The longest run back from any one light fitting being 53 inches, having said that one light will be directly over the bath and another in the shower, I don’t fancy mains in the shower.

Give me your views.

By the way I agree with PompeySparks comments concerning you, only trouble is, if you’ve been wiring all day long the last thing you’ll want to do is go on a chat forum to discus wiring problems all night long.

 

[Steve]

glad im of some help. Anyone want an apprentice in South Yorkshire?

Some transformers might need protecting with a 3amp fuse, perhaps the ones they sell at Wickes (otherwise the guarrantee may be void). Quality transformers though, shouldn't need additional protection on top of a 6A MCB. Often, in a fault, the 2 protective devices wont discriminate, MCBs are much faster acting than fuses. If the transformer you buy says protect with a 3A fuse, then do so, for guarrantee purposes. Use an FCU and connect it between the transformer and the switched supply.

Maximum load for a 6A MCB is 1380w. This is the maximum you can connect to that MCB regardless of how many fuses etc there are downstream.

Mains are definitely easier to install, though theres nothing to stop you buying a small transformer and LV fitting and fitting it above the shower if it makes you feel better. Apparently LV lights give nicer light, not that anyone would ever notice, but they take longer to install etc.

Bathroom zones is not something i'm strong with, perhaps someone else can say what would be allowed in what zones.

 

[ban-all-sheds]

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http://www.niceic.org.uk/downloads/NL139supp.pdf
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