Lights group flashes 3 times 5 secs apart

Hi and thanks,
For many months when switched on our hall lights (7 in the group) will flash 3 times 5 seconds apart and then stay off.
Then for a few months they'll work fine.
We bought the house with cbus in it. Installed about 1999.
What does this mean? How can I fix?

 

I'm sure you are correct - thanks Nick.
I have 7x50W Dichroic downlight globes.
If I remove 5 globes the last 2 stay on.
I've tried to find out which lamp offends but it doesn't matter which globes I leave out and in which sockets, 2 globes stay on, 3 leads to flashing then off.
Should I just replace them with 7W LED globes?

 

assuming that its NOT a universal dimmer based on the age of the install, then 7 x 50W is too high.

200W max per 1A channel is the rule of thumb I work to (240W resistive load in basic numbers - and yeah I know we should work on 230V not 240V - just keeping it simple).

If its a four channel dimmer @ 2A/channel then 7 is fine.

3 should work OK as this is only 150W.

Nick can answer this - what is the effect of exceeding capacitance?

 

Sorry for the delay and thanks for your help & interest.
The dimmer's description is -
DIMDU4 - DIN Rail 4 Channel Universal Dimmer, 2A per channel

Incidentally I did try the 7x 7W LED globes and they work (without flashing) but are not as bright or as good as the 50W.

Any suggestions?
I don't need them to be dimmable.

 

I recommend have the downlights changed to dedicated LED types. Be careful to get ones that are suitable for C-Bus (LED's with a separate driver is a good indicator, all in one /integrated units are more problematic in my experience) or there may be turn off issues.
The LED lamps whilst often advertised as equivalent, are usually less output than the halogen. That said, I've found the Osram ones to be the best / brightest & most reliable.

 

Thank you very much.
Yes, the LED ones I have are not as bright and I will change the downlights as you suggest.