Hi, Can anyone help?

A friend of mine is having problems with her hot water supply from her Ideal Isar He24 combi boiler.
When you draw of hot water the boiler is kicking in and initially the water is very hot, but it then quickly drops to being luke warm. If you adjust the flow at the draw off tap you can get the water to become hot again but only at a very slow flow rate. This gives a problem when using the shower as you can't get a decent flow of water through without it being cold...
I have read a few blogs suggesting that cold showers are a one disadvantage of combi boilers but this problem has only just come about since Christmas, previously it was fine.
The CH works fine, although it is very rarely used. The apartment was empty for a couple of weeks over Christmas with the heating timed to come on intermittently which was the first time it had been used for a while.
Having read a few similar blogs, I thought it might be the diverter valve. My thinking being that if it hadn't been used for a while to divert to the CH it may have become stuck, as there would have been no DHW draw off during this time.
So I removed the actuator head and checked the travel of the valve mechanism push rod. There seemed plenty of travel circa 10mm but I manually operated it a few times to make sure it was operating freely. I then replaced the actuator and checked the system again, no change.
The valve seems to be correctly working and diverting the water according to the demand (DHW on/off, CH on/off, both on/off) it’s just the temperature.
The only other things I can think of are;
a) the diverter valve may be blocked, so although working correctly, the flow of water through it is restricted and therefore reduced?
b) The heat exchanger plate is blocked again reducing the flow of water through the plate and limiting the hot water output?
c) The core temperature of the water has been reduced by the cold weather and the heat exchanger can’t cope at full flow. (If this was the case, I don’t understand why it runs hot initially)?

Please can anyone shed any light on what they think the problem may be (and how to resolve it)??

addmb, February 2010

Hi I have a similar problem with this type of boiler, in that, hot water is inconsistent, but also the radiators come on when not needed or programmed to do so. Any suggestions why this is happening please.

Angela, August 2017

Diverter Valve not working
Chocked Diverter Cartridge
Plunger Changeover pin sticking

These can all be addressed by replacing the cartridge which contains the pin and IS the valve (minus the housing, which, if broken, believe me you would know about!)

colin dooley, February 2013

i have changed everything on my he24 boiler only now i have to buy yet another actuator because it has stuck onto heating so cannot get hot water anyway :-(

alan, October 2012

These boilers are a gas engineers nightmare!! it could be one of several things!!! I went to a job last week with this exact same problem, as we engineers work on initial thought processes and as experience dictates it should be the diverter valve needs changing!!

However on closer inspection and lots of internet information gathering on theses boilers I have reserched a list of possible problems for no hot water on these things. not only is it impossible for the engineer to diagnose every aspect of why the boiler isnt doing its job, in turn to thoroughly check each individual process in would not only cost the customer large amounts in cash for us to stay at the property to try and find what it is, but large amounts in turn to order every part possible which it could be and to fit these would go into the thousands!!!!

So my thoughts are save the money and get a Worchester Bosch installed!!!

List of faults for the rest of you engineers to consider in future are:

Actuater not working
Diverter Valve not working
Chocked Diverter Cartridge
Plunger Changeover pin sticking
System needs flushing due to Diverter sticking as this wasnt done correctly and install
Thermister Fault
Heat exchanger blocked
PCB knackered.

Could you serriously or want to give a quote for all these parts supply and fit and can you imagine the customers face when you hand it to him/her!!!!

Thought so!! I would stay away from these boilers full stop in the future!!!!!!

gs517116, January 2011

the heat exchanger is blocked when changing get serial number as there are two different types of heat exchanger

phil, March 2010

An engineer is calling on me tomorrow, watch this space.

graeme, February 2010

i have the same problem, They are crap boilers.

Graeme, February 2010