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baxi 105e intermittent DHW (Read 13958 times)
Kev
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baxi 105e intermittent DHW
Nov 29th, 2009, 10:54am
 
Hi All , only just found this great resource ( so at least I have the baxi to thank for that  Wink)

Ok we have a baxi 105e and its been in the house at least 5 years ( worked fine all this time  )  however its just become unreliable in delivering hot water .
From reading on here I checked the pushrod is working ok on the DHW pressure valve and the microswitch seems ok .
we`ve since sussed that hot water is delivered ok if the CH is off but if the CH is running its only luke warm to cold.
I`ve also noticed a loss in pressure recently and whilst my head was in there I saw a small water leak from just below the Diverter valve operating head ( this only drips when the CH is on ) it must have been doing it for some time as the circlip that holds the Diverter operating head on has  little rust spots .
Questions :
1) Anyone any idea what the hot water fault is ?
2) is the tiny leak below the diverter valve enough to drop the pressure to zero or is that going to be the expansion thing I read about ?
3) anyone know what washer or O ring sits between the diverter valve and its operating head as Im reluctant to take this apart until I have the bits required to put it back together.

Any help/advice much appreciated

Kev
     
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Kev
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Re: baxi 105e intermittent DHW
Reply #1 - Dec 9th, 2009, 1:14pm
 
OK .. no answers here set me off on the direction of changing the likely suspects .
So now I have a new diaphragm for the CH and DHW fitted as well as a new diverter valve operating head ....however this has not cured the problem .( neither Diaphragm was split at all )

CH works fine but the DHW will only run this way ....I take the old diverter head apart ..re-set the brass contact point to the "up" position put it all back together and fit to the boiler ...the hot water will run fine however when I switch to CH the operating head motor turns ok and allows hot water into the CH system however if I try and get hot water now ...I cant ...its as if whatever sets the diverter valve head to CH wont allow it to switch back to DHW ..it cannot be the head as it does the same with the new one.  

Does anyone have  a clue of where to look next as I`m stuck ....  
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« Last Edit: Dec 9th, 2009, 1:14pm by coldwash »  
 
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Re: baxi 105e intermittent DHW
Reply #2 - Dec 9th, 2009, 2:00pm
 
Don't do domestic boilers, but I would be looking at thermistors and flow switches.
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Kev
Re: baxi 105e intermittent DHW
Reply #3 - Dec 11th, 2009, 3:49pm
 
Little update on this :

...

The diaphragm attached to the pink part was fine , initially when I checked the pin was moving out and operating the microswitch ok ....however after taking the back part of the DHW Manifold off I noticed a small chrome pin just about protruding from inside the pink bit ...took the large nut section off to find this

...

a very gucked up pin ... totally not moving ...so basically when the  pin from the DHW diaphragm moves to contact the microswitch it should also allow the pin above to move forward and close off the flow to the CH ...this is why when I ran the tap, hot water was running into the rads ...

fingers crossed all is working and all it cost was a Diverter head ( I have a spare now ) and two inexpensvie diaphragms  Grin

incidentally anyone else reading this that has a small leak from under the part where the Diverter operating head fits on ...take the head off with removal of the U clip, undo the large brass nut ( from where the U clip went ) and you will see a chrome rod passing through a small ( 5mm) white nylon bush ..on top of this bush is a tiny rubber "O" ring ...in my case the nylon bush had  slid out a little and was not compressing the rubber O ring enough to make  a tight fit on the operating rod.( these parts are not shown on any diagram I have seen )

Apologies to the experts for the incorrect terms however had I seen a list of the correct bits and bobs I would have termed this better.

thanks to all those that posted replies on all the other threads concerning this boiler type .

BTW next time this thing messes about its off the wall so if anyone has a good reccomendaton for a combi do let me know.....

Ta        
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« Last Edit: Dec 12th, 2009, 8:47am by coldwash »  
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plthatfunkymusic
Re: baxi 105e intermittent DHW
Reply #4 - Mar 6th, 2016, 9:04pm
 
Hi Kev

Thanks for your post.  I think we have exactly the same problem with our 105e as you had back in 2009.  Firstly the radiators started warming up whilst the DHW is on (annoying during the summer months), and now increasingly the hot water requires high flow rate before kicking in.  It's now very difficult to trigger the DHW at all.  I've ordered a DHW diaphragm, but believe it may well also require a clean-up of the pin you have described to fix the radiator heating issue.   Did you have to drain the central heating to remove the nut you have shown, or was that just limited to the DHW circuit?  Obviously keen to not flood the house.  Thanks for any help you can give.  Smiley
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