boiler won`t switch off.

[malc19591]

Hi,
Hope someone could help with my heating problem. i have an alpha 240p boiler thats constantly calling for heat, as soon as i switch the power on the pump starts, the primary flow switch operates and the boiler lights. it then stays on until switched off at wall. also pressure rises alarmingly. dhw barely warm unless flow reduced to a dribble. dhw valve and diaphragm o.k.
tried disconnecting remote stat and no different .thought it might be divertor problem , but would pump start immediately? please help!

 

[Agile]

It sounds as if the DHW demand switch on the front of the diverter valve is sticking on for some reason.

Check it and let us know.

Tony

 

[malc19591]

hi,
disconnected switch, boiler still lights immediately.

 

[malc19591]

sorry Tony,
forgot to mention. have pressure drop in system,have to re pressurise every 2 to three days, but can`t find any evidence of leak.

 

[gas4you]

Are you sure there is no demand from external controls? Check at boiler connection.

Have you tried disconnecting the switch on top of the DV with the red wires?

 

[malc19591]

no demand from external stat,
with primary flow switch disconnected(red wires) boiler does not light, although pump runs and primary spindle operates switch, no dhw either.
with p/flow switch connected and plunger held down manually, dhw works,
i.e. turn on tap and boiler lights.

 

[malc19591]

starting to think it must be pcb faulty, anyone know test procedure?
i have multimeter .

 

[gas4you]

Could be pcb, but Alpha pcb's are usually fairly fault free.

 

[malc19591]

thanks dave,
only other thing can think of is weak/damaged spring in divertor, still does not make much sense?

 

[malc19591]

just realised, when boiler is lit the pilot light ignition is constantly sparking.
any clues?

 

[gas4you]

Boiler is not recognising the pilot is alight. Could be a simple loose connection or still a very outside chance of the pcb faulty.

One needs to be in front of it to diagnose properly.

 

[malc19591]

thanks Dave,
will persevere and let you know.
thanks for pointers.

 

[gas4you]

Just to double check, we are talking of the 'P' version and not the 'E'?

If definately the 'P' what is the fan doing? Does it spin slowly when just pilot on, or is it running full tilt?

 

[malc19591]

yes def "p" model.
the only time i have just pilot is with power off.
as soon as power switched on boiler lights fan full speed and boiler flat out.
can`t adjust flame with manual ch or dhw stats on front of boiler also constant sparking from pilot ignition unit.pressure rises until power switched off manually. if boiler thinks pilot not lit would it allow gas valve to open?

 

[gas4you]

Confusing one.

Try 'wiggling' the knob on the gas valve that you press to light the pilot. There is a micoswitch on this that activates the fan and spark etc. The fan should come on at full speed to start with, then when pilot is established, slow to tick over.

Could be this is stuck in the on position.

Otherwise starting to look more like the pcb.

We need Paul Barker to pick up on this post. He's the Alpha expert on here