need help with Low Voltage transformers

[billywolfe]

I have just replaced a transformer which is a heavy old type (magnetic with coils) with a small lightweight electronic transformer - http://www.screwfix.com/prods/39220...rmers/Halolite-35-105w-Electronic-Transformer . The output rating on the old transformer is 12v 105VA. The output rating on the new one is 11.4V - eff. 9.2A, 35-105W/VA.
The old transformer output went to the first of 5 20w LV lamps which were daisy-chained (in series). I have connected the output from the new transformer in the same way. Is this OK? The reason I ask is because I have used electronic transformers before and have run outputs from the transformer to each lamp in parallel. The length of cable from the transformer to the last lamp in series is about 2.5 metres.

Thanks in advance for any help.

 

[stem]

It depends upon the voltage rating of the lamps.

What are the lamps for? are they part of your house, or some Christmas tree lights or something similar?

If they are 12v lamps the transformer needs to be in parallel with the lamps, so that all of the lamps get the full 12v. If however, the lamps are only 2.4V (12/5) then in series would be the way to go.

This seems a rather strange set up to me. Are you sure they really are in series? If they are, and one lamp was to fail, or you took one out, they would all go out. Do they?

 

[billywolfe]

It depends upon the voltage rating of the lamps.

What are the lamps for? are they part of your house, or some Christmas tree lights or something similar?

If they are 12v lamps the transformer needs to be in parallel with the lamps, so that all of the lamps get the full 12v. If however, the lamps are only 2.4V (12/5) then in series would be the way to go.

This seems a rather strange set up to me. Are you sure they really are in series? If they are, and one lamp was to fail, or you took one out, they would all go out. Do they?

The lamps are 12v. They are a set of 5 Wickes LV downlights (a few years old) in a bedroom. I have taken 1 out and the other 4 stay on, so I guess they are not in series...I have not got the floorboards up so can't see the wiring. I just thought they were as only 1 cable actually joins into the transformer. Anyway, the lamps are working OK, with no loss of brightness at all, so I guess the wiring must be OK?

Many thanks for your help

Tony

 

[ban-all-sheds]

The old transformer output went to the first of 5 20w LV lamps

//www.diynot.com/wiki/electrics:voltage-bands

which were daisy-chained (in series).

No - they were in parallel. They would have to be or they would only have got 2.4V each, and if one lamp failed they would all go out.

//www.diynot.com/wiki/electrics:parallel

I have connected the output from the new transformer in the same way. Is this OK?

Yup.