Conservatory Cavity Wall Query

[shaggie16]

Hoping someone can help.
New conservatory being built, with 450mm dwarf cavity wall, brick outer, thermalite inner, no cavity insulation.
I need to have power and lighting cables run, and my initial thouhts were in capping on the thermalite which would then be covered by dot and dab plasterboard.
I am told not allowed to do that, (something to do with horizontal runs of cable x mm from the floor) and have been told they should be run in the cavity. Well, OK, that's no bother and will use conduit to do so.

Now, rightly or wrongly, I want (purely for effect) some dimmable low voltage halogen "guide lights" set recessed in to the wall on the inside - These in fact:

20W G4 LV Reflector|Recessed Wall Lights

My problem is this. They are 20W G4 lams, and there will be 8 of them on a dimmer. My initial plan was to have one transformer and run the lot off that, but the low voltage cable run would be way too long I think and the voltage drop would be hideous.

How can I get around it? Multiple transformers, yes, but being a cavity wall, there won't be space anywhere to put the extra transformers, so where can I put them? They are small items, but obviously in the cavity secured to the thermalite is a no no because of damp. I don't really want to lose 2cm of space behind the plasterboard, plus that would be a nightmare if (sorry when) one of the transformers failed.

SO, any ideas how I can achieve this?
I have looked for other ways of doing it, ie LED fittings, mains voltage halogen fittings, but the requirements are a shallow recess as these are going into a cavity wall, and they must be dimmable. Most LED guide lights I have seen of similar design are cold white and are NOT dimmable.

Please help!

Thanks in advance

 

[shagbite]

employ an electrician who knows how to design a lighting circuit.

 

[telectrix]

you can run cables horizontally between sockets under the plasterboard. fit the transformers behind the lights.

 

[shaggie16]

Whilst I have every intention of using an electrician, I always want to avail myself of possibilities. My experience of any trade, be it electricians, plumbers, even my own, whoever you speak to will often recommend solutions they are themselves familiar with. That in itself is of course good practice, but it doesn't neccessarily give me the widest choice.

So, whilst I am looking at what is available and how I can use it, I ask the question above.

 

[shaggie16]

Telectrix - thanks for your reply. My only concern here is that the lights are deeper than the dot and dab, so will require a little notching out of the thermalite to fit them. How can I fit the transformer behind the light if that is the setup?

 

[kingeri]

You can't change the laws of physics, you'd need them to physically fit, if you're on about those thermalite bricks then you can notch into them if required but it's not ideal on a new build.

 

[shagbite]

Whilst I have every intention of using an electrician, I always want to avail myself of possibilities. My experience of any trade, be it electricians, plumbers, even my own, whoever you speak to will often recommend solutions they are themselves familiar with. That in itself is of course good practice, but it doesn't neccessarily give me the widest choice.

So, whilst I am looking at what is available and how I can use it, I ask the question above.

well, forgive me, but when someone comes on here, asking how they can 'get around volt drop', my spidey sense starts tingling and i reckon they're gonna have a crack at it themselves.

 

[shaggie16]

well, forgive me, but when someone comes on here, asking how they can 'get around volt drop', my spidey sense starts tingling and i reckon they're gonna have a crack at it themselves.

I see. I do know how to get around voltage drop, I have a degree in physics, but I don't want to use 6mm cable, and what I was struggling with was whether I would simply need to rethink what I actually want to achieve because although multiple transformers placed nearer the lights will also combat the problem, I am unsure on whether it is possible to either hide the transformers somewhere, or just change tack and look for LED fittings. However, as stated, I cannot find any LED fittings that are warm white and shallow recess.

To be fair, I didn't ask how I can get around voltage drop. I identified it as a problem, and asked how I could place the transformers, or if there were alternative but similar fittings such as LED that people were aware of, that are warm white and shallow recess.

 

[telectrix]

the lights ask for 45mm depth. i'd cut right through the thermalite, thats 100mm, so loads of space for transformers.and LED lights are a good option.

 

[shagbite]

I see. I do know how to get around voltage drop, I have a degree in physics, but I don't want to use 6mm cable, and what I was struggling with was whether I would simply need to rethink what I actually want to achieve because although multiple transformers placed nearer the lights will also combat the problem, I am unsure on whether it is possible to either hide the transformers somewhere, or just change tack and look for LED fittings. However, as stated, I cannot find any LED fittings that are warm white and shallow recess.

To be fair, I didn't ask how I can get around voltage drop. I identified it as a problem, and

asked how I could place the transformers,

or if there were alternative but similar fittings such as LED that people were aware of, that are warm white and shallow recess.

i'm afraid my answer remains the same. you should find an electrician who has the knowledge and ability to carry out this installation satisfactorily.

 

[shaggie16]

Telectrix - so just so I am clear in my own mind with regards to seeing what products I can use - I can get the electrician to cut right through the thermalite into the cavity, and put the transformer there? That won't affect the strength of the wall or indeed the waterproofing? The transformer would be ok sat in the cavity like that?

If that's the case, is it also possible to mount the transformers in the cavity itself just under the windowboard? If one failed, I could easily remove the window board to have it replaced. I just assumed the cavity would get too damp to do that?

Once again I should point out that I am not planning on doing this myself, I simply want to know what products I can use so I can get the best choice.

 

[HandySparks]

However, as stated, I cannot find any LED fittings that are warm white and shallow recess.

Why not just fit G4 LED lamps to the fittings you've found. They're certainly available in warm white. Not sure about dimmable, you may have to experiment with some samples.

 

[tom79bmth]

Hiya will the transformers fit in a metal knock out box and put a blank on the front so you can access them

 

[shagbite]

that'd look pretty rough, to be honest mate.

 

[Engineer54]

If these fittings have already been purchased, then try and get them replaced at the store they were purchased from, as clearly they are not suitable for this installation. Replace them for full voltage fittings of whatever lamp type is available.

As the old saying goes, you can't fit a square peg into a round hole. You will always end-up with a real pig's ear of a job!!!

 

[telectrix]

but , the again, he's working with a dwarf wall in a conservatory. not like it's holding up much weight. nothing wrong with cutting right through the thermalite.

 

[Engineer54]

but , the again, he's working with a dwarf wall in a conservatory. not like it's holding up much weight. nothing wrong with cutting right through the thermalite.

Wouldn't that be destroying the integrity of having a cavity wall, ...there are after all 8 of them i believe?? I certainly wouldn't want to install TX's in the cavity. Far better to have a fitting that is suitable for it's location....

 

[shaggie16]

Thanks for the ideas. Nothing has been bought yet - I am not doing this job myself. I'm purely trying to get ideas of what will and won't work, so I can make sure that when I sit down with the electrician, I know all ideas have been thought about.

So, LED bulbs - good idea. Cutting through the thermalite could also work.

With regards to the mains voltage fittings, my concern here is recess depth. But are we saying then, that I shouldn't limit my thoughts to shallow recess because of the wall contruction, as cutting deeper into the thermalite isn't an issue? If the fitting is IP rated would it matter if it went all the way through the thermalite into the cavity?

A greater allowable depth would certainly open the world of opportunity with regards to which fittings would work.

 

[Engineer54]

Thanks for the ideas. Nothing has been bought yet - I am not doing this job myself. I'm purely trying to get ideas of what will and won't work, so I can make sure that when I sit down with the electrician, I know all ideas have been thought about.

So, LED bulbs - good idea. Cutting through the thermalite could also work.

With regards to the mains voltage fittings, my concern here is recess depth. But are we saying then, that I shouldn't limit my thoughts to shallow recess because of the wall contruction, as cutting deeper into the thermalite isn't an issue? If the fitting is IP rated would it matter if it went all the way through the thermalite into the cavity?

A greater allowable depth would certainly open the world of opportunity with regards to which fittings would work.

Don't be bloody stupid!! Why do you want light fittings on such low walls anyway, why not wall lights at a suitable height on the existing wall the conservatory is attached too?? If you're dead set on having these low mounted lights, purchase suitable full voltage fittings rather than LV ones that require a TX, or fittings that incorporate an integral TX!!

 

[shaggie16]

I did say in my initial post that I assumed things cannot go into the cavity! So the question remains then. Whatever fitting is used in these low level lights, will, at least in part, need to be notched out of thermalite block behind the dot and dab plasterboard. So WHAT DEPTH is permissable to notch out of the block to incorporate the recessed fittings?