Vokera Linea 28 fault with hot water

[clarkerothwell]

hi, searched and couldnt find anything similar to this fault -

Heating works fine
When demand for hot water boiler fires ok to full gas rate (10mb) then drops after about 3 secs to low rate and stays there, doesnt cut out ever, water runs at a constant 42 degs. Never gets any hotter and boiler never returns to high rate.

Flow rate is set to roughly 10 ltr/ min
WP is 21 mbars

Parts changed :

Primary thermistor
Domestic thermistor

Flushed domestic heat exchanger - re-fitted then then tried again - no diff
Replaced Domestic heat exch - no diff

Has annybody had this fault??

Also to note, before i exch thermistors i plugged a new one in dry and left existing one in for the domestic and boiler ran on full rate and water got red hot !!

I then replaced domestic therm and it returned to jut low rate??

When i ran it with primary thermisitor dry it didnt make any difference, boiler still ran on low rate for h/water.

Any Ideas would be great, cheers.

 

[DP]

What work/ repairs if any, carried out previously?

 

[clarkerothwell]

eh up DP, cheers for reply mate.

Only what i did (i'm gas safe reg), diverter valve service kit fitted about a year ago.

 

[clarkerothwell]

i thought it was typical linea dom ht exh blocked, but it wasnt cutting out, but i removed and flushed anyway, did get some debri out but only usual amount.

I borrowed new one and exh but still same !

 

[clarkerothwell]

been informed its the non return valve in the right hand manifold of the domestic heat exch - bloecked or broken, part number - 2908 in vokera manual

 

[petit_pablo]

See my reply in your other thread.

 

[Agile]

It would help if you only started one thread and made it clear at the outset that yo are an RGI.

Trade questions are best asked in the CC.

Tony

 

[clarkerothwell]

will do in future , cheers, and thanks again pablo.