Ideal Isar 24 issues

[mattd2]

Hi there,

I hope someone can help.

I have an Ideal Isar 24 (yes I know they are rubbish ) - it was installed approx 3-4 years ago.

Until recently it's been working great - no issues whatsoever. At first I noticed the heating pipes were getting warm in the night, and hot water was warm not hot - so I checked and changed the diverter valve. The old one looked in fairly good condition but the shaft was sticking.

Now the diverter has been changed I no longer see the rads getting warm, but there is still a problem.

Most of the time the taps run warm to hot rather than very hot, or it takes a long time for the hot water to arrive. Occasionally there will be very hot water and them warm to hot water. The kitchen taps usually run slightly hotter than the taps upstairs.

Just now - when DHW was on, the water was coming out of tap very hot, I can hear the pump going and if I look at the CH pressure valve it's goes from a steady bar to slightly above, then drops to just below 1 bar and back to 1 bar again (I can hear the pump changing pitch when this is happening). The burner was running, stopped, water went warm, press remained at 1bar, burner started again, after 30s or so water was hot again and pump/CH pressure changing. CH outlet pipe remained cool when this was happening.

Could this be a blockage in the plate heat exchanger?

I guess it is not a thermistor problem because there are no errors whatsoever reported.

I have the old black PCB not the new orange one.

If I swap the plate heat exchanger is it worth also swapping the PCB out for the new one?

Any ideas appreciated!!

Thanks in advance
Matt.

 

[mattd2]

Another bit of info - when the hot water is running I've notices the CH flow return heats up slightly (CH flow out pipe does not change)

Bearing in mind the above about CH pressure ups and downs when the DHW is running, would this suggest that DHW is getting pushed back into the CH system via the flow return/pump and therefore the plate heat exchanger is blocked up?

Flow of water through the hot taps is very good.

 

[45yearsagasman]

Matt, I would definately remove the plate exch and most of these can be cleaned.Make sure the primary side is thoroughly cleaned and this may resolve your fault.No point in replacing a pcb that is showing no faults.If you are capable of this it will cost you nothing but your time.Don't forget to isolate correctly.Hope you have enough clearance under the boiler.

 

[mattd2]

Many thanks for the reply - I will try that next.

The boiler is in a cupboard so will have to take the cupboard off 1st. Luckily it was fitted with servicing the boiler in mind so not too much of a job. At least it means have plenty of clearance below

 

[Happyplumber]

The honeywell actuator valve,the pcb are inhertently unreliable on these boilers and are changed out frequently to the extent that partscenter etc keeep at least 20 of each in stock

 

[CORGIGASMAN2]

the problem is that the isar has an inbuilt pre heat which will fire up when the plate heat exchanger needs to keep hot a waste of gas but you can buy the optional extra kit which when fitted turns off the preheat,
the reason the central heating is slightly warming is that when the preheat is operating it is also letting by into the central heating