Vokera Vision 25C

[Theweeknd]

Hi, having some problems with a boiler that gets H/W, it starts of at around 40 degrees then gradually goes down (is this the heat in the boiler at the present time or the heat that should be going out to the H/W?)

Sometimes it even goes totally cold and then after 5 to 10 minutes fire ups again to h/w

Possible causes, (I think)
1. Thermistor
2. Sticky diverter vavle?

Can anybody help?

 

[Theweeknd]

please?

 

[vulcancontinental]

Neither. Possibly a blocked plate heat exchanger. Set the boiler for heating and hot water then run the hot water and watch the display. When running hot turn the three way isolating cock below the boiler to off as quickly as possible while watching the display. The display will change from showing the DHW temperature to the primary flow temperature. If this rises quickly to over 82-85 degrees = blocked plate.

 

[Theweeknd]

Neither. Possibly a blocked plate heat exchanger. Set the boiler for heating and hot water then run the hot water and watch the display. When running hot turn the three way isolating cock below the boiler to off as quickly as possible while watching the display. The display will change from showing the DHW temperature to the primary flow temperature. If this rises quickly to over 82-85 degrees = blocked plate.

Thanks will try this shortley, its for a friend and they said British Gas came out to do a service and thats when the problem started, whats the chances of them coming out to diagnose?

 

[Theweeknd]

Are you referring to the three way valve beneath the pump?

 

[ianmcd]

Neither. Possibly a blocked plate heat exchanger. Set the boiler for heating and hot water then run the hot water and watch the display. When running hot turn the three way isolating cock below the boiler to off as quickly as possible while watching the display. The display will change from showing the DHW temperature to the primary flow temperature. If this rises quickly to over 82-85 degrees = blocked plate.

Not often I disagree with @vulcancontinental but I have never seen the three way valve on a vision, all the ones I have seen just have the water throttle shut off cock

 

[James1991]

Not often I disagree with @vulcancontinental but I have never seen the three way valve on a vision, all the ones I have seen just have the water throttle shut off cock

That's weird Ian, I've never seen the throttle type valve on a vision. It's always been the 3 way type.

If the fault has only happened after BG had serviced it, perhaps it's just the flow rate needing adjusted. It could be the plate thou the way you've described how the boilers behaving.

The hw thermostat is turned up?

You could try phoning them and asking them to come back out.

 

[vulcancontinental]

The early ones had an on off tap, later to up the spec the traditional filling loop was included Ian