worcester bosch greenstar 24i junior

[rogtheprisonofficer]

HELP .....hello everybody, i have a WB GREENSTAR 24i JUNIOR, the CH is working but the DHW comes on and fires for about 30 seconds and then goes cold. i have looked at the diverter valve and that operates as it should i.e. when CH is demanded the valve goes down and when i turn on the hot tap it rises. i looked at a pdf installation and commissioning manual which has a flowchart, it looks to me that the boiler is in a failsafe mode in that the water temperature maybe too high which results in the boiler shutting down for safety. although i don't have a thermometer my hand tells me that the water is somewhat higher than the preset 55 degrees. i know the temperature is factory set so what can i do? i think i have included all the information in this post so can anyone please help? Rog

 

[boilerdoktor]

If the stepper motor is rising then the flow switch and stepper ( div valve) motor is working! Is the pump running?

 

[rogtheprisonofficer]

wow, thanks for the quick reply, yes the pump is working, Rog

 

[rogtheprisonofficer]

i was thinking maybe the DHW temperature sensor??? could that have failed? Rog

 

[boilerdoktor]

Sensors extremely rare on worcesters to go wrong. Turn your heating off, turn hot tap on, does the flow get hot ( left hand 22mm pipe)to the central heating?
Do you get any flashing lights on boiler?
Is it still in warranty?

Press the lower left hand button and hold for 10secs till it lights, turn ch control to max, what happens?

 

[rogtheprisonofficer]

yes the flow gets hot, no flashing light and unfortunately its no longer in warranty however it might be my imagination but the hot water seemed to stay hot for longer

 

[rogtheprisonofficer]

i did that and the boiler fired and the blue light flashes quickly five times, then pauses then does it again etc

 

[rogtheprisonofficer]

oh, but no hot water at all now, not even for that initial period

 

[rogtheprisonofficer]

it just occurred to me the pressure guage is right on the border of green and red, almost 3 bar, is that significant?

 

[rogtheprisonofficer]

could there be an air lock in the DHW heat exchanger? if so how do i get it out?

 

[rogtheprisonofficer]

ok, anyone who is reading, after speaking to a worcester bosch technician he assured me that i need to replace the DHW heat exchanger as the problem is caused by DHW overheat and the situation im experiencing is a failsafe. this makes sense so we have now purchased a new one. he said it is fairly straightforward to replace but i would welcome any advice in doing it. pleeeeeeeease

 

[Agile]

He has sold you a part!

I am surprised that you are so easily "assured" of whats wrong.

Well replace it and if its not solved then ask for further advice.

It might well be blocked but they can easily be cleaned out without needing to buy a new one!

Tony

 

[ChrisR]

The first one has blocked fairly quickly, so clean it out(strong kettle descaler, or search the forum) and keep it for next time.

 

[onlyfitidealboilers]

whats the best chemical to clean a plate heatex DS40??

 

[rogtheprisonofficer]

thanks fellas, im just refilling now so watch this space