I have an Ideal Isar HE 24 and am having a problem with it. Its about 4 years old i have just changed the DHW thermistor and diverter valve and actuator and it has sorted all my problems but not my DHW problem which is, when i turn on any hot tap on in my house the boiler will fire up and start to heat the hot water but after 20 second or so it will drop in pressure and the water becomes scalding hot then the burner will go out then it starts all over again doing the same sequence over and over again while this is happening i have knocking and whooshing noises coming from it. before i changed the diverter valve and thermistor it was banging so violently i was scared to switch it on but i only get the noises on the hot water side of it now.
Can anyone help

Neil, March 2008

Hi
I had the same problem with mine and we changed the heat exchanger and it solved all the problems.Before mine was making the same banging noise and it is due to the heat exchanger getting scaled up.
Hope this helps

Adrian Hardy, November 2010

If it's banging when you turn it on you need a new igntion starter should sort out loud banging noise.
This is due to gas not igniting properly

Mo, April 2010

There may also be other solutions if the system is not clean, see: http://www.diynot.com/forums/viewtopic.php?t=95213

rob mort, April 2008

The banging noise is "kettling" and is due to the build up of scale in the boiler especially with the aluminium heat exchanger of the Isar. Only remedy is to add an anti-noise additive, and repeat if necessary.

rob mort, April 2008

You could try the diynot.com forum there's already some threads on this...

Jarv, March 2008