When I turn on the tap in kitchen for hot water the boiler does not start up. But it's fine when I use taps upstairs. Had probs for about a year now sometimes it works but 95 percent of the time the boiler won't kick in. Also it's OK when I put it on timer or constant the pressure is fine and radiators are all fine. Just won't kick in when I turn kitchen tap on. Any advice would be great. I have a baxi boiler

HI Darthroon

Certainly any time a timer is entered into an equation, you need to look at the timer so I'd definitely double check this.

In other cases like you present I've found that low water volume/flow can be an issue for some of the newer wall hung or condensing boilers.

Try this:

Remove the aerator at the kitchen faucet.

Run water without the aerator in place.

Does the boiler turn on now? If so, clean the aerator and reinstall... see if things are improved. If boiler doesn't fire then next thing I'd suggest is a quick call over to the Baxi boiler manufacturer's technical department and chat them up. In most cases, these guys/gals are just waiting there to help their customers... should have paperwork nearby the boiler.

Back to you...

Mark