IDEAL ISAR Condensing Boiler problem

[drdr]

My daughter has one of these horrible boilers, it is about two years old.
For sometime she have been complaining about the delivery of domestic hot water. She says that she turns the tap on, the boiler lights and delivers some lukewarm water before the boiler switches off. the water goes cold, the boiler then fires up again and you get more lukewarm water, this cycle repeats itself until she turns the tap off. She never gets really hot water.
I asked her to try the central heating and she thought that was working normally.
To the best of my knowledge, the boiler has not been touched (thermostats changed etc)
Any ideas anyone?
Thanks

 

[gas_man_gaz]

sounds like it could be the plate heat exchanger

 

[Agile]

I expect the installer did not bother to clean the system!

Just like one I went to today.

Tony

 

[drdr]

plate heat exchanger? is that serious?
The system was recently drained and refilled following radiator valve changes, the water was very clean. It is since then the the problem has arisen though.

 

[fela kuti]

the heat exchanger can be removed and cleaned.the main problem is removing the sludge from the pipework and radiators which will clog the heat exchanger up again.
you would have to powerflush the system not cheap.

 

[gas4you]

And awkward to get at to remove on an Isar, unless you are doing it everyday and used to it

 

[idealnumber1]

which pipe is getting hot when you run a hot tap
if its the flow - diverter cartridge
if its the return - plate heat ex is blocked
if its the cold water inlet - then your hot an cold pipes are fitted the wrong way

 

[shambolic]

The likely cause has been identified on here. But the boiler has worked fine until you drained and refilled system which you never said in original post. So how is the boiler horrendous it's worked ok for nearly 2 years with no one looking at it.
Ps have you had it serviced annualy as per manufacturers instructions?
The fault will likely be plate blocked or if rads heating up on hw demand the div valve cartridge!

 

[DP]

shambolic, if the diverter cartridge was defective i.e. rads were heating during hot water demand, surely the bourner would not shut down?

Fail to see how a service would cure this problem as some annual services carried out on boilers comprises a chat with cutomer over tea and pressing a few buttons on the FGA. All looks very proffessional but achieves zilch.

 

[shambolic]

shambolic, if the diverter cartridge was defective i.e. rads were heating during hot water demand, surely the bourner would not shut down?

Fail to see how a service would cure this problem as some annual services carried out on boilers comprises a chat with cutomer over tea and pressing a few buttons on the FGA. All looks very proffessional but achieves zilch.

Your right mate but have had these syptoms where cutomers have no bypass rad or bypass and all trvs shut down in summer can cause it to cut as overheats with a little heat going down the flow pipe first. But would more than likely be a Plate hex problem due to poor water quality. As for the service on an Ideal isar/icos we recommend it to be stripped and checked each year regardless of telegan readings to clean the s Trap and the sump and check the integrity of the insulation panels the ionisation/retention probes and the spark electrode

 

[drdr]

Thank you all for the advice. I am sure that between you you have identified the problem, could be any or all of ...
1. Plate heat exchanger
2. sludge in the system
3. hot and cold inlets wrong way round.
4. defective diverter cartridge
Cleaning the plate heat exchanger sounds like the most probable, sorry I forgot about the system being drained. I was there at the time, and the water seemed as clean as if it had just come out of the tap, I was amazed. I would put any amount of money on the pipes being the correct way round as the plumber who installed it is brilliant. Unfortunately he is not around to help with this problem.
As far as the diverter cartridge is concerned, I don’t even know what it is. What you are telling me is that I have to get someone in, not the sort of job I can do myself.
The comment I made about the boiler being a ‘horrible’ type is as a result of the negative things I have read about it on this site.
Thanks for your interest

 

[kevindgas]

most likely crud in the plate - very common fault and it reduces the flow through the plate H/E and the diverter cartridge.

be aware that the likely outcome of removing either will be a replacement PCB / control panel within a week of it being done!
last 3 we have been to, we have seen this happen.!
get ideal to fix the crock of Sh.....

 

[Garfeild]

most likely crud in the plate - very common fault and it reduces the flow through the plate H/E and the diverter cartridge.

be aware that the likely outcome of removing either will be a replacement PCB / control panel within a week of it being done!
last 3 we have been to, we have seen this happen.!
get ideal to fix the crock of Sh.....

Make sure you cover all the electrics and pcb etc when removing the phx,this will stop the pcb being damaged.

 

[kevindgas]

Make sure you cover all the electrics and pcb etc when removing the phx,this will stop the pcb being damaged.

i have taken the PCB out completely and it still dies!! and even kept every bit of water off the wires!

these boilers are a crock of Sh11te period

 

[Paul Barker]

To be fair I have had to fix quite a few of these, although I have arrived where they are in a condition that they need a pcb I have never had to fit a new pcb as a result of my working on the appliance.

I couldn't really do my job at all if so.

I once killed an alpha pcb because I exposed the whole thing while I adjusted co2 rather than just work through the gromet holes. Of course I dropped a screw on the pcb while boiler running. Short circuit, puff.

I killed a cf18 drenching it but the vokera pcb I drenched with it worked after the hair dryer treatment
. Sadly the cf18 didn't. Had a very forgiving tsm at the time. "How did it happen?" I had it under a boiler and the ntc which I thought was reasonably secure must have been at the end of it's thread and drenched everything" "Oh well, I prefer people who are honest!" Now keep cf18 far side of kitchen!