I have a Baxi Luna 24fi that's probably 12 years old. Was serviced about 4 months ago and was fine.
The heat works fine, but I'm having problems with the DHW (no hot water). I noticed if I turn on the washer set on hot, the unit ignites and works. If I then turn in the bathroom tap and shut off the washer, the unit continues to heat the water. I also noticed if I turn on the tap and shower, the unit will heat the water. However, turning only one tap will not activate the unit. From reading around, it sounds like a flow issue. Any ideas?