the hwhe during c/h operation heating up suggests that the diverter valve is not moving over fully and needs replacing. its letting by not allowing enough hot water through to heat the dhw while there is a demand
the heat exchangers are expensive parts and can take a good couple of hours to change. they also take ages to order in, its best done through the manufacter and ferroli are a nightmare to deal with. the life expectency of a modern combi is 8 years, this is the governments opinion.
for a flat i...
1) clipping the pipe further will give the pipe more support and stop any possible vibration
2)are the taps 1/4 turn, is it happening as the tap closes? this may be water hammer
The problem is with your heat exchanger. its not worth repairing, ferroli are bringing out a new modena which will have a 5 or 7 year guarantee with the manufacturer. i would have one of those installed when the problem gets unbearable. i wouldnt get any other ferroli cause the optimaxs and...
This might be standard operation. Most combis have a pre-heat setting which delivers a quick blast of hot water, the water will then go cold as the water is reheated. you can take it off this setting....read your manufacterers instructions for details
It is likely to be an external control such as your timeclock/roomstat. use a short bit of cable to link out your roomstat at the terminals, if the boiler calls for heat its the roomstat thats faulty.
It sounds to me like the hot and cold are blending, most probably at the shower. With a hot tap running check your shower to hear if water is flowing through the shower. If you can hear water flowing through the shower you need a double check valve fitted to your hot pipe supplying the shower...
I would recommend you go with the combi. A viessmann vitodens 30kw to be precise. The unvented system is far better to give you your shower as they give mains pressured hot water but is more expensive and more space consuming and unnecessary for a 1 bathroom house. Being a 3 bed house im...
Make sure both the rad valves are open. Have you re-bled the rad since turning it back on? Have you got a TRV on the rad? Is the TRV stuck closed.... remove the head and bounce the pin up and down to release it.
The TRV if fitted is the most probable cause
I would recommend you get an engineer to service your boiler. As part of the service he will re-pressurise your expansion vessel. Lack of charge in the vessel is the cause of your problem.