Glow worm combi 30 xci f14 fault .

Discussion in 'Plumbers' Talk' started by paul down, Jun 21, 2018.

  1. paul down

    paul down New Member

    Hi Guys , new to this forum and hoping someone can shed a bit of light on my boiler issue.
    My glow worm 30xci is playing up . When you run the shower /hot tap it runs fine for about 2 mins then runs cold for about a minute then runs fine again until you turn of the shower .

    I ve monitored the boiler during this cycle and it comes up as F14 (which is CH flow temp is greater than 95'). I ve read some threads that say it could be the plate to plate hx, or the 3 way valve or motor or even pump or PCB . ( The Pcb was changed in oct 2017 before we bought the house).

    When at the boiler, the boiler comes on when demand is there and when touching both the CH flow pipe and the HW outlet you get a cold CH flow pipe and and hot HW flow pipe as expected . Then after about 2 minutes the CH flow pipe goes extermely hot very quickly and brings on the F14 fault , Boiler turns off then after about 1 minute fires back up and runs ok. Whist the hot water is running we are also getting the radiators warming up .
    Have had a gas safe engineer out who did nt get the f14 fault to appear but adjusted some pressures and basically ruled out a blocked HX . He suggested i change the HW thermistor if i had any further problems which i have but to know avail.( weirdly i can t get hold of the same engineer and am still yet to pay him for his initial house visit despite attempts to contact him).
    I guess my long winded question is what is the more likely failing component in the above situation , HX? Diverter valve ? motor ? or PCB again. There is no abnormal noise when running the hot water so i m assumming flow thru the HW side of the HX is ok , so does this mean the prob could be in CH side of the HX ? . Sorry about the long winded thread but could really do with some major pointers.

    Cheers look forward to any replies of help/advice or just experiences of the same thing .
  2. kiaora

    kiaora Well-Known Member

    It’s most likely the blocked heat ex.
    This can force the water through the diverter and to the heating ,
    Then with the Boiler on high flame and the restricted flow, it overheats ....

    It’s not too difficult to do, but you really need to be a competent diy to attempt.

    The heat ex needs to be removed and filled with descaler dilute H2SO4 type
    Leave to ‘cook’ then flush out with water,

    Always best the get 4 new seals, if you can

    KIAB likes this.
  3. KIAB

    KIAB Well-Known Member

    Use to know a old plumber who used Kilrock kettle descaler.:eek::confused:
    Last edited: Jun 23, 2018
    kiaora likes this.
  4. paul down

    paul down New Member

    Thanks for the reply Peter .
    It really was very helpful , was nt sure how the rads were warming up without the diverter valve operating but now I can see why a blocked HX can cause this .
    Cheers Paul
  5. kiaora

    kiaora Well-Known Member

    If it’s letting by so much that the rads are warming up, it may be the diverter valve sticking,

    It’s not too difficult to take out and clean, put a bit of silicone grease on the pin, reassemble, job done, perhaps try that first?

    Turn off mains water drain boiler, take our the clip that says “yes”! To remove head.
    Undo castle like screw, remove diverter assembly, take a photo, take it to bits and clean it, reassemble, no parts required.


    Ps. If the Boiler won’t work after you do this, what happens is, you dislodge one or the sensor connections getting head off, happens all the time!
    KIAB likes this.
  6. paul down

    paul down New Member

    Just a quick update . Removed plate to plate heat exchanger totally cleaned out with one shot (twice ) and flushed thoroughly. Refitted with 4 new seals tried and tested all now working fine .
    Just one note for anyone else attempting this. No need to remove gas flow pipe as per manual as exchanger can fit over the diverter valve easily . Thanks for any replies all very helpful .Paul .

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