Vokera compact 24 water hot/cold/hot/cold/hot/cold

im going to be replacing this piece of 5h1t next year,

i had it installed in 2002/03 and has been nothing short of a sore head since,

i have over 10 scottish gas job sheets and vokera job sheets from all the break downs, these have 90% of the time been due to the hot/cold/hot/cold water, im sure thats what killed my digital quartz shower last year due to its constant water temp change,

i canceled my boiler care after the last time it was repaired so now its down to me to fix it myself,

anyone any ideas where to start?

the green light is on and showing all is ok, but its clearly not,

also forgot to say, if i turn the tap on lets say bathroom sink good flow (i dont mean i put it on full blast just enough to fill the sink) water starts coming through and as it gets heated the flow goes to a trickle then i need to speed up the tap to avoid the boiler from shutting down, whats causing this to slow down to almost a stop?

Amazing! you have a boiler that's continually breaking down so you cancel a contract that should mean you get it repaired for nothing.
Hot-cold-hot-cold is usually due to dirt, it's probably all round your system and gets caught up in the HW heat exchanger. Realistically you probably need your system cleaned as well as a new h/e.

i canceled the contract due to the cost, now its down to me to fix it,

id say dhw thermistor

Nath

In my case I think it was the minimum gas pressure set too high so the boiler couldnt regulate the flame strength. Vokera plumber worked that one out - I would recomend him.

He also changed the thing that measures the temp of water because was covered in debris - said that would interfere with measurement of water temp.

Am not a plumber but think that if flame isnt allowed to be weak, the water will over heat and deposit limescale in HE and pipe. I think descaling might help with low pressure but am also trying to work out how to do this

are you in a hard water area ? or a soft water area ? if hard water then probably lime scale, if soft water will be a sensor problem, Your boiler is a decent boiler and can be repaired easily with a decent engineer

plate heat exchanger blocked (if its the compact A) or venturi needs cleaning/replacing.

Im with picasso on this one, if its the venturi you'll need a rgi to fix,

if its overheating due to restricted (dhw) domestic hot water heat exchanger, theres a check you can do yourself. as follows:


Run dhw tap but stay at the boiler and watch the temp display rise on the front of boiler.

The burner will cycle on and off as the main temp sensor is getting too hot, (hence getting cold water briefly, then hot again when burner lights again)

Watching the burner through the glass on the front, when it switches off briefly, immediately isolate the cold mains going into the boiler, which will change the temperature display on the front from reading the dhw temp to now reading the central heating water temperature.

If it reads anthing above 85'c, your dhw heat exchanger will need to be cleaned or replaced. This may be a temporary fix as system may need cleaned too and it may happed again.

Incase you didnt know how to isolate the water going into the boiler. its done by turning the black handle 90 degrees anti clockwise. It is situated under the boiler and at the furthest pipe on the right.



edit... oops sorry i thought it was a vokera linea you had, wrong boiler.