12V Downlighters Voltage Drop

[3guk]

Hey Guys,

Having a few problems with voltage drop in my lounge, I don't have a particularly big lounge, I have 8 x 30W downlighters in there and a few are noticeably dimmer than the rest, I have ruled out old or knackered lamps by replacing them all with the same batch.

It appears that there are 2 paralleled runs of 4 downlighters connected to a Halolite HA-S300 - 300W transformer. The cable is 1mm conductor 2 core I think.

I could do with getting up there to have a better look, is this the best way to wire them ? Is there a way to overcome this voltage drop? I've seen things wired up in a radial way, with each cable from transformer to 12V fixture being the same length, would this be a better way for me ?

Cheers

 

[Taylortwocities]

Yes, or use thicker cable for the longer runs.
or
position the tranny in the middle and use the same length cable to each.

Didn't know you could get 30 watt MR16s but (assuming you mean 35W) then you are running 3 amps to each lamp. You'll drop quite a lot of volts on thinner wire.

 

[RF Lighting]

Run all the wiring at LV and step down to ELV adjacent to each lamp.

 

[3guk]

So are you suggesting individual transformers ? I thought most people hated these things, I know in my old house they seemed to fail pretty frequently ?!

To be honest with you I thought the cable was pretty think, what sort of cable to you recommend ?

 

[333rocky333]

Didn't know you could get 30 watt MR16s

Some manufacturers are phasing out 50w they are being branded as Energy saving 30 watt and 45 watt

 

[3guk]

They are 35W lamps, sorry for any confusion !!

Is there anything wrong with connecting up each lamp individually in a radial style, making sure every cable is the same length, surely this would make any voltage drop equal, admittedly it requires a bit more cable than paralleling.

 

[333rocky333]

In my opinion a 1 output 300 W tran should not be wired to individual lights.
Wire lighting does it that way and thats why the wires are so thick.

A 300 watt can be wired to a splitter unit with suitable cable, then seperate cable from each protected way.
There is a 2 core 2mm cable designed for this.

A transformer with seperate protected outputs to each is more suitable.
Or individuall trans.

If a fault develops or the cable is overloaded, unless the cable is rated to take the full 300 Watt 12 volt, it could overheat and the transformer internal protection not shut it down, as the overload is still within the trans output limit.

 

[ban-all-sheds]

The cable is 1mm conductor 2 core I think.

About 44mV/A/m....

 

[properleckie]

8X35=280 w/12v = 23.3A on 1.0mm2 volt drop will be high.

why not run from trans. in as large a cable as will fit terms (4mm2 if poss), to a JB in middle of first 4 lamps and loop on to same again for other 4. short lengths of 1mm2 virtually no volt drop.

 

[3guk]

I'd not thought of that Properleckie, I think I may end up going down this route, appears to make the most sense.

 

[333rocky333]

The output from a 300Va tran is up to 25 amp, so what would protect the 1mm cable if a short in the fitting allowed 20 amp or so to flow

 

[3guk]

A 300 watt can be wired to a splitter unit with suitable cable, then seperate cable from each protected way.
There is a 2 core 2mm cable designed for this.

What should I be looking for when trying to buy one of these "splitter units" is there a name for them ?

 

[Aragorn84]

if hes running 10 x 30w lamps its flowing 25A in normal operation never mind a fault condition...

That 1.0mm cable must be getting rather toasty!

 

[ban-all-sheds]

It appears that there are 2 paralleled runs of 4 downlighters connected to a Halolite HA-S300 - 300W transformer. The cable is 1mm conductor 2 core I think.

 

[3guk]

if hes running 10 x 30w lamps its flowing 25A in normal operation never mind a fault condition...

That 1.0mm cable must be getting rather toasty!

Aragon, there are only 8 lamps, and they are split into 2 x 4 parallel lamp runs, still I'm guessing 11.6A isn't particularly good for 2 x 1mm cable. I'll look at getting this swapped out asap, seems the guy who owned this place before me was a bit of a rubbish tinkerer, you wouldn't believe the amount of rubbish that I have found.