12v vs 240v downlights

[bernardgreen]

When a lamp filament is cold its resitance is lower than it is when hot. This means that when a voltage is applied to a cold lamp ( when it is turned on ) the current is higher than would be expected from calculation of watts divided by volts.

For some types of filament lamps the initial current can be as much as ten times the normal current of the lamp when at normal white hot temperature. For most it is between 2 to 4 times the current.

This must be taken into account when choosing the switch to be used.

 

[sparkyspike]

12v halogens give a crisp white light, good for kitchens and bathrooms. 240v halogens are a warmer light, better for other rooms. 12v run a bit hotter and cost more to install (with a transformer). They use approx the same energy. I like to use soft start transformers to prolong life of the lamps.