Keston C45 - Question Regarding Thermostat Setting

14 Jan 2007
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United Kingdom
Good Evening,

I have a Keston C45 that supplies hot water to 2 zones. Zone 1 is Underfloor Heating and Zone 2 is domestic hot water. The front of the boiler has a control knob for each zone that allows the temperature to be set from off to about 75 celsius.

Recently, when adjusting the Zone 1 (CH) control the temperature only goes to a max of 25 celsius when set to the Max setting. The Zone 2 (HW) still functions normally. This means that the boiler will not fire to supply hot water to the UFH because it thinks the thermostat is set too low. Any ideas what is causing this?

Any help appreciated.
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Its a Keston - bin the ****box.

Possibly a dodgy connection/short making the boiler think the weather sensor is connected.

Either way - there is no point spending any money on this thing.
Thermostat controller is defective. We have replaced several in the last few years on a C55. You will need a new panel board. I have a few spare if you wish to pm me.

In the meantime you can wire up the 2 zones on the thermostat that is still working. It is just a single wire (purple) from the top of my head.

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Very common that the potentiometers go on these. One symptom is that the set point temperature flashes on the display now and again when nothing is touched.

A replacement potentiometer does not require the fascia PCB to be replaced.

A link between the two switch lives will provide a temporary fix, preferably done outside of the boiler (I.e. In an external electrical junction box if this is feasible).


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