Adding a dimmer to light switch controlled by two circuits

[Dirleton]

I have a light switch in the island in my kitchen which powers two chandeliers located above the island. In order to cut the power on/off for this light switch I must cut off two circuit breakers (numbers 25 and 29) located in the breaker box. Also controlled by breakers 25 & 29 is the front doorbell. Power still remains for both the doorbell and the light switch if only one of the two breakers is cut off. Following is a link which shows two photos of the light switch Kitchen Island Light Switch - https://photos.app.goo.gl/iAdHFLE3Nizuh4MK6 I want to change the light switch to one with a dimmer. Will there be a problem given that the doorbell is also controlled by the same two circuits? And, if not, is there a particular type "light switch with dimmer" that I should use? Thanks for your help.

 

[w0z]

Every circuit should be isolatable with one breaker only. If you can't isolate the lights with only one breaker it needs sorting out before you start thinking about fitting a dimmer.
It sounds like someone has modified the wiring and bridged the out of the two breakers or circuits, it could be in the consumer unit or the two circuits are connected together elsewhere. and as it stands in my opinion it isn't safe.
Is it (the light) on a 2 way switch or is there only one switch controlling it?
What else is connected to that circuit? What about other lighting in the house?
The type and quantity of lamps in the chandelier will determine what sort of dimmer will work, but the good news is that once the wiring is sorted the switch can just be replaced by a suitable dimmer.

 

[Dirleton]

Thanks for your response. In response to your questions: (1) There is only one switch controlling the light in question; (2) Two rooms, the living room and the kitchen, seem to be affected by breakers 25 and 29. Also note, the electrical for the doorbell is in a small alcove just off the living room. Here's what happens: (a) cut off 25 (29 still on), nothing happens; (b) cut off 29 (25 still on), nothing happens; (3) cut off both 25 and 29, the kitchen light switch (the one in question) goes off (but nothing else in the kitchen goes off) and all the receptacle connected lights in the living room go off, as well as the doorbell. NOTE: the kitchen and the living room are next to each other. Hope this helps.

 

[w0z]

Not really (much of a help)
It's unlikely the doorbell is involved, someone has taken a feed for the doorbell from the lighting. (Ideally there should be a fused unit feeding the bell transformer). I can't see why anyone would or should ever take a second feed to the doorbell.
Same reply as above, someone has bridged the two circuits, maybe when alterations were done? (Taken a feed off one circuit and connected it to the other perhaps??)
Get a spark in to check it out, it may (or may not) be as simple as disconnecting one live loop feed (and a neutral) from one of the ceiling fittings.

 

[brianmoooore]

Definitely needs attendance by an experienced electrician.
It's not so dangerous that I'd advise you to switch off the consumer unit and use candles until one can attend, but it should be sorted sooner rather than later.