dimming low voltage halogens safely

I need to power a number of lighting circuits, consisting of 4x 50W low voltage halogen lights, which therefore totals 200W. The UK mains supply is a nominal 240V, and so given this voltage, it would appear that a 1A C-bus dimmer circuit could provide sufficient current to power a circuit using up to 240W, which is clearly more than sufficient for my needs. However, I have heard that due to the start up current consumed by the transformers for these lamps, you do need to allow some margin. Would therefore a 1A C-bus dimmer be safe to use on a 200W low voltage halogen lamp circuit? It would obviously be safer to use 2A dimmers, but this would increase the number of c-bus dimmer units required considerably.

Any help or suggestions will be most gratefully received.

Thanks

 

Not that this answers your question, but I thought everyone had standardised on 230volt? (Even though we all still call it 240v!!!)

 

There is a table outlining the number of transformers (and lights) that can be used with the dimmers.

Typically four 50W LV Halogen (ie down light) can be used on a 1A dimmer channel if the right Tx is used.

There is also a document on the forum on how to calculate the number allowed and it should give guidelines on the headroom that you need to allow.

Mick

 

What is meant by "the right tx" ?

Also, where do I find this document which helps to calculate the number of units allowed?

Thanks
Neil C

 

tx = transformer

electronic transformers also have capacitance that has to be accounted for with the dimmers

Try using the search function for the forum. This topic has been covered so many time now that it is not funny any more

http://www3.clipsal.com/cis/lit_installtraining_dimmer.php3

Mick

 

Transformer losses

Hi Neil
the transformers also have losses, so they need to be taken into consideration. Hopefully you have electronic which typically have about 5% loss so about 3w for 50w lamp. A trick to keep losses and capacitance down is to wire 2 lamps onto a 105VA transformer, then you halve your transformers required. The maximum length allowed in-between the transformer & the lamps is 2m.
The old magnetic transformers have about 10w loss each.
To endorse what znelbok says, use the search function, there is heaps of threads on this, covered in much more detail by John C
Regards
Matthew

 

LV Lights

I have installed numerous systems in the UK and never had a problem with 4 50w lamps and 4 seperate 60va transformers, other than the usual transformer failures. Are you an installer or end user ?

Michael.