davetheglitz
Electrician
Screwed up on this one.
Customer wanted 10 small halogens in the dining room ceiling. Because of the small access hole and piped underfloor heating upstairs I elected to run 35W halogens in banks of 2/3 from 35-105VA Aurora transformers - all transformers to be wall mounted - cupboard to go around at a later date. 4 transformers fed from a 400W dimmer. Wiring to the lamps in 1.5mm.
When connected several of the banks didn't work. Some banks pulsed on and off, others would work up until max brightness and then shut off. During the setup, two transformers went bang and tripped the MCB.
After consulting the instructions (who reads them until the end!) it appears that the transformer need to be run towards the top end of their rating (>50W for dimming), the dimmer must be run at greater than 75% of it's max capacity and that only 2m of lead to the first light is allowed - I had considerably more than this - reasoning that a couple of volts dropped would not be noticeable and would be fairly even over the whole ceiling.
I eventually got all lights working reliably by connecting two banks of 5x20W bulbs to each transformer - but I'm not sure it is bright enough.
The only explanation I can think of that makes any sense is that the extra lead length has an inductance which causes an instability. When two banks are connected together at the transformer the inductance is reduced allowing stable operation.
Has anyone else had similar problems in the past - and does anyone have any easy fixes?
Customer wanted 10 small halogens in the dining room ceiling. Because of the small access hole and piped underfloor heating upstairs I elected to run 35W halogens in banks of 2/3 from 35-105VA Aurora transformers - all transformers to be wall mounted - cupboard to go around at a later date. 4 transformers fed from a 400W dimmer. Wiring to the lamps in 1.5mm.
When connected several of the banks didn't work. Some banks pulsed on and off, others would work up until max brightness and then shut off. During the setup, two transformers went bang and tripped the MCB.
After consulting the instructions (who reads them until the end!) it appears that the transformer need to be run towards the top end of their rating (>50W for dimming), the dimmer must be run at greater than 75% of it's max capacity and that only 2m of lead to the first light is allowed - I had considerably more than this - reasoning that a couple of volts dropped would not be noticeable and would be fairly even over the whole ceiling.
I eventually got all lights working reliably by connecting two banks of 5x20W bulbs to each transformer - but I'm not sure it is bright enough.
The only explanation I can think of that makes any sense is that the extra lead length has an inductance which causes an instability. When two banks are connected together at the transformer the inductance is reduced allowing stable operation.
Has anyone else had similar problems in the past - and does anyone have any easy fixes?
