Baxi 105e Combi Instant CH Problem


Postby Trixsales » Fri Apr 02, 2010 7:30 am

My boiler is very reluctant to switch from DHW to CH. When both DHW and CH are in operation when I run the hot water the green indicator remains lit and the boiler will not return to supply the CH demand - only if I run the hot water tap once again to the point that the boiler fires up to meet the demand will the green indicator light begin to flash - once the tap is turned off, a little while later the CH will then operate - during the switch over I notice a ticking sound towards the left site of the boiler which then stops and the CH operates. I suspect the diaphram in the 3 way valve assembly - any ideas ??

If the diaphram is the cause would I need to drain the boiler to carry out the replacement ?? - I replaced the DHW diaphram approx 6 month ago.

Tnks
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Postby htg engineer » Sat Apr 03, 2010 7:46 pm

The ticking noise will be the motorised head (on top of diverter) when everything is off - no call for heat, the diverter sits in DHW mode, if the CH isn't working correctly it could be the diverter or the motorised valve sticking.

However it is a combi and priority is given to the hot water, so if you run a tap it will heat the water store, before the CH will come back on.

Try turning Pre-heat setting off, and see if CH comes on as soon as the hot tap is closed.


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Postby Trixsales » Sat Apr 03, 2010 8:27 pm

Many thanks for replying to my problem - As you suggested I turned off the pre-heat and with the hw tap closed the boiler immiedietly reverts back to CH once the ticking stops - I suspected the possibility of the diverter motor being a [u]possible[/u] cause of the problem, and I duly ordered one today.

Would I need to drain the boiler to replace the CH Diaphram and the Motor assembly ??

Rgds
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Postby htg engineer » Sun Apr 04, 2010 7:31 pm

What I was trying to say - is that the boiler could be working as it should.

If the diverter reverted back to CH when the pre-heat was turned off - everything is working ok.

If you run the hot tap and the pre-heat is on, when you close the hot tap the pre-heat will heat the water store - so there will be a delay for the CH coming back on - I think the pre-heat light flashes during this time.

All combi boilers give priority to hot water.

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Postby Trixsales » Mon Apr 05, 2010 7:35 am

Many thanks for your reply - perhaps i've been unable to explain the situation correctly - I am aware of the priority issues and sequence of events regarding DHW - the problem is that with both CH and DHW on where the boiler reverts from CH to bring the water store up to temp the burner ignites and the DHW indicator flashes as it should - once the temp is reached and the burner extingushes the DHW green indicator stays permanently ON - [ not flashing ] and the boiler does not revert back to the CH mode. If I then turn on the hot water tap again to create a demand on the DHW the burner ignites and the green indicates flashes as normal, turning the tap off will in most cases force the boiler back [ after the ticking sound stops ] to CH mode - it seems as if there is a reluctance to switch from pre heat mode back to CH.

I hope that this helps to clarify the situation.

Best Regards
Trixsales
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Joined: Mon Sep 10, 2007 9:24 am


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