Potterton combi boilet and system - Model Suprima

17 Apr 2006
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United Kingdom
The settings on the boiler, wall mounted in the kitchen have not been changed since it was installed two years ago - when the house was built. Since then we have noticed that the boiler "fires up" even when there is no water being drawn. Also, the temperature in the shower (mixer tap) fluctuates from freezing to boiling. Same in the upstairs bathroom where the hot tap runs hot then cold. No problems at all with the heating. Any advice re the fluctuation of temperature would be greatly appreciated.

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The shower is a mixer tap, but the bath is two individual taps which feed into one spout.
A Suprima is not a combi boiler. If you have a combi boiler what make and model?
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Maybe check what type of boiler you have as Potterton don,t make a Suprima Combi. When you say the boiler fires up when no water being drawn, if its not a combi it will be heating a hot water cylinder which may be calling for heat or you have a faulty valve which is jammed on.

Correct me if I'm wrong, ta

We have a Potterton Suprima in the kitchen and a Boilermate 2000 under the stairs.
The Suprima is a conventional heat only boiler.

The Boilermate is a thermal store ie it stores a large quantity of hot water - this is then used by the heating or the hot water at the taps.

It is normal for the boiler to fire up from time to time (to keep the store at high temperature)

If the central heating appears to function OK that would indicate the boiler is probably OK (although the Suprima has to be the worst boiler ever designed !)

Since the boilermate is not a common system you are best calling Gledhill on 01253 474444 to locate an engineer to resolve the other issues.
Dont they have a blending valve which sometimes sticks?

Agile - Where would I find the blending valve so that we can check to see if it is stuck?

Gasguru - many thanks for this clarification. Bovis get no awards for using the best products!!
most likely problem is scale build up in the combimate these units suffer from scale big time down here in bournemouth
Very simple system on the 2000 - there is DHW sensor on the hot outlet of the plate exchanger.

Looks as though the plate exchanger is constantly kept warm - as soon as the sensor detects a drop in temperature it knows a hot outlet must be open.

Presumably it starts/stops the plate pump to maintain outlet temperature at a sensible rate.

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