Vokera linea 28

[Sam]

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

[Roger Hayter]

It could be some "eco" setting on the hot water programme that fails to heat a store of boiler water sufficient to maintain hot water output until the boiler has come on. This is especially likely if the central heating is running at a relatively low flow temperature.

[Fredxx]

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.

[Graham Harrison]

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".

[Halmyre]

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.