No heating with Potterton

[Jamie_P]

Hi - help needed...


I have an issue with a Potterton 28i

Selected Hot water and central heating

Have hot water, burner switches in and out when hot tap is run

Central heating water pressure = 1.25 Bar

No heating


LEDs:

Power on - Illuminated

DHW mode - Illuminated

Central heat mode – Never illuminates

Red LEDs display temp (~70C), no fault LEDs.


Pump (Grundfos 59926502):

With power off, removed bleed, not seized.

Has power supplied to it (pump has no LEDs on it)

Measured approx. 100ohm resistance across Neutral and Live

It is very hot


Control:

Thermostat – OK (tested by bypassing)

Built in timer/controller – Tested and OK

PCB – exchanged but fault still present



If the pump is at fault would I still see the heating demand LED come on? (As said mine never does).

Could it be constantly requesting hot water and so never heating?


Any advice welcome!

Cheers

 

[Gasguru]

Could it be constantly requesting hot water and so never heating?


Any advice welcome!

Cheers

Quite possibly or stuck in pre-heat.

These models are a flawed design. Expansion vessels (used as a thermal store), DHW flow switch/diverter assemblies are a frequently a problem.

 

[CBW]

When you have bypassed the thermostat, how have you bypassed it and does it fire up? Have you tried the push rod in the diverter assembly? Ruled out daft things like ch temp dial on fascia and selected ch on selector on fascia?

 

[Jamie_P]

Bypassing the thermostat didn’t make it fire up.
CH temp dial on max.

 

[Ihavenojob]

Turn the pre heat off and see if the hot water demand light goes out, if it does you could have a hot tap dripping. If it doesn't go out then chances are the microswitch on the differential valve is closed circuit, possibly caused by a jammed or leaking diff valve. If the pump was knackered the boiler wouldn't give hot water.