Pump still running after heating and water shutdown

[10051550]

Hi Guys,

My heating pump is still run long after the heating and hot water have gone off

If I switch off the mains to the whole system and back on, its back to normal and stops

Is this an overrun issue ?

Frost Thermo / 3 way valve / Drayton programmer ?

Any ideas ?

Thanks for replies in advance

 

[ianmcd]

some great engineers on here but we dont have crystal balls, which boiler which Drayton programmer ??? post some pics they are a lot better than words

 

[10051550]

Hi Ian,

It’s a mistral boiler house oil boiler ( not combi ) Honeywell 3 port mid position valve , Drayton LP722 programmer - so fairly traditional setup . Frost thermo out in garage with boiler

Heating and hot water ok but pump still running until I reset system via mains

 

[MeldrewsMate]

Old oil boiler is unlikely to have a PCB controlled pump run-on, but may have a thermal run-on, though this is unlikely to have failed in the way you described.
It is possible that someone may have fitted a boiler economiser, or similar. Some were designed to cause the pump to run-on until the temperature at one of the heating pipes dropped below the set value. Could it be this little bugger that's latching on a pump overrun relay?
Photos would help, and to eliminate or confirm the above try tracing the cable from the pump. Post a picture of where it leads. Are there any 'cables' or sensors strapped to the main boiler pipes?

 

[10051550]

So it’s 9:51 and heating has been off for 1.5 hours - if I feel pipe where bleed screw is there is vibration , pump running - and diverted valve head casing hot , all pipe work cool

If I switch off system at mains and back on , diverted valve whirls and pump stops

Oil boiler is 9 years old but not combi

 

[10051550]

Any thoughts anyone ?

 

[ianmcd]

which model of Mistral boiler ?

 

[oilhead]

Is this a 'new' fault or has it always occurred?
The Mistral boiler will be a simple affair. Switched live into boiler from programmer, via 3 port valve and no pump overrun. OP says turning off mains will make 3 port valve close and pump stops. I would suspect wiring error in junction box, or no HW off wire from programmer and live picked up from switch wire, but boiler and pump should be fed from same terminal so you need to find source of power to pump. Junction box should be 1st port of call. Also check if there is a pipe thermostat in the frost stat circuit. This may be wired incorrectly.

 

[dilalio]

Needs probing out but as asked above, if this is a 'new' fault, due to a defective programmer or mid position valve, then the boiler should also be firing.