I have anproblem with my Vokera linea 28 boiler , work no problem with central
heating , but when running hot water , mainly the shower , it gets to temp
fine then after a couple of minutes the water starts to run cold then heats
back up again . At this moment in time i have replaced the safety thermostat ,
both thermistors , fitted a service kit to the divertor valve and checked the
heat exchanger isnt blocked , the problem still exists although does seem to
run for longer when the temp setting is turned down , is there anything else
that could be causing this issue . Thanks Sam

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On 26/01/2020 14:44:02, Sam wrote:
I have anproblem with my Vokera linea 28 boiler , work no problem
with central heating , but when running hot water , mainly the shower
, it gets to temp fine then after a couple of minutes the water
starts to run cold then heats back up again . At this moment in time
i have replaced the safety thermostat , both thermistors , fitted a
service kit to the divertor valve and checked the heat exchanger isnt
blocked , the problem still exists although does seem to run for
longer when the temp setting is turned down , is there anything else
that could be causing this issue . Thanks Sam

I presume this is a thermostatic shower? If so then it might be worth
opening a tap with a slow flow while the temperature is being stabilised
and the HW flow varies.

It might also be worth checking the flow rate where the boiler doesn't
sense enough flow to fire up.

I had an issue where the gas valve was "sticky" and wouldn't modulate at
low gas rates, where I'd get a flame-out.

On Sun, 26 Jan 2020 14:44:02 +0000, Sam
m wrote:

I have anproblem with my Vokera linea 28 boiler , work no problem with central
heating , but when running hot water , mainly the shower , it gets to temp
fine then after a couple of minutes the water starts to run cold then heats
back up again . At this moment in time i have replaced the safety thermostat ,
both thermistors , fitted a service kit to the divertor valve and checked the
heat exchanger isnt blocked , the problem still exists although does seem to
run for longer when the temp setting is turned down , is there anything else
that could be causing this issue . Thanks Sam

I had a similar problem (with a different combi stilly boiler).

Combi boilers have a safety feature; if the flow/pressure gets too low
the water will get too hot so it stops heating so that you don't get
burned/scalded. In my case a partial solution was to run another hot
tap at low flow whilst having a shower. Then I changed the shower head
and the problem went away because the old shower head was blocked by
"fur".

On Sunday, January 26, 2020 at 2:44:04 PM UTC, Sam wrote:
I have anproblem with my Vokera linea 28 boiler , work no problem with central
heating , but when running hot water , mainly the shower , it gets to temp
fine then after a couple of minutes the water starts to run cold then heats
back up again . At this moment in time i have replaced the safety thermostat ,
both thermistors , fitted a service kit to the divertor valve and checked the
heat exchanger isnt blocked , the problem still exists although does seem to
run for longer when the temp setting is turned down , is there anything else
that could be causing this issue . Thanks Sam


Our Vokera has done that since day one. I put it down to the crazy pipe runs in our old house but it does seem to have got worse in the last year or so. Damn thing's only about 20 years old; does nothing last these days?!?

Our mains water pressure is quite high, so I don't believe it's cutting out because of a limited flow of water.

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Halmyre