I have little halogen downlights in the bathroom ceiling. They run off two 'transformers' in two groups of four lights. ie 8 lights.
Sometimes three bulbs in one of the groups will come on after a delay and the fourth just flickers as if it can't quite manage to properly come on. Usually this string of bulbs needs to be fully on before the second string will come on. Sometimes they all come on OK after three seconds or so but one lot of four followed by the second lot. We seem to be replacing bulbs frequently.

Any ideas what's happening. Doesn't seem as if there is enough oomph in the system. The bulbs are 18-20watts.

I reckon that's a transformer problem - will have a word with my m8 who's an electrical wholesaler for a second opinion

Are the bulbs the correct wattage for the LV power packs ? -- ie not too high a wattage or too low.
If they are correct then replace the LV power packs.

Alternatively consider converting to 230v GU10 bulb holders and the latest high output LED bulbs. We did this after the outer protective lens exploded off a bulb and left a circular burn stair carpet. You can now get the LED bulbs in warm white or blue white.

We did that in our kitchen.
Used the same housings and got the 24ov sockets off the bay for pennies.

the LED's consume a total of approx 30watts, as opposed to the 280 the halogens used. quite a saving with no real loss of light.
A few bulbs have gone in the past 3 years, but again not expensive (though more than the halogens)

Bear in mind that its a bathroom so it may be low voltage for a reason.

Be careful with your terminology when ordering though!

When most people talk about low voltage, they are in fact talking about Extra-low voltage!

Wyn

The lamp are all connected in parallel, so within a group of 4 a single lamp flickering can not possibly be the transformer otherwise it would affect all the lamp equally.

The single flickering lamp is mostly like caused by poor connection either between the lamp and holder, or between the holder and the wiring. Because of the high currents and high temperatures involved with low voltage lighting, a slightly bad connection will quickly degrade as the contact surfaces get burnt.

There should be no dependency between the two transformers in terms of switching order. If there is it suggests you have a fault on the mains side wiring.

Low voltage halogen lights draw quite a current and the contacts oxidize and arc causing flickering.

Changing the bulb replaces one side of the contact with a clean conductor and scrapes the other one clean but the problem returns quite quickly.

It is also intermittent which makes fault chasing almost impossible.

Solution is to clean the contacts which is , IMHO, impossible so I replace the bulb holder and bulb - they are available from wholesalers cheaply.

To prevent it occurring in the first place stop the oxidization by using contact grease - I use a silicone based one and with new holders and bulbs after the grease is applied they are noticeably brighter demonstrating that oxide exists even on new components.

Cheers

PS Don't believe it? Try smearing Vaseline on your torch contacts - it gets brighter.

Cheers!