combi fires up on its own

[valcra]

worcester bosch 240 rsf

shortly after dhw demand is satisfied and hot tap turned off, boiler fires up on its own and heats rads without another demand for dhw or ch.

boiler also fires up during day/night without dhw or ch demand and outside of programed times.

thanks in advance of any answers, valcra.

 

[simb82]

answers to what

 

[Agile]

Just after hot demand its usually caused by a dead leg.

See FAQ on this site.

Although that would be fairly unusual on your model.

Tony

 

[gas112]

Microswitch on divertor valve is activated eitther stuck or pin not returning after HW demand and boiler thinks a tap is still on

 

[valcra]

thanks for your replies,

gas112: new complete diverter valve fitted a little under a month ago. have watched actuator during operation and is working fine but still have problem!!

Agile: without ripping up floor coverings and floor boards i cant say definitively but to my knowledge, no dead legs!!

anyone: " could faulty dhw or ch sensor or both be the problem? "

 

[gas112]

If new divertor then disconnect clock if its still firing then its the microswitch sticking

 

[Agile]

To discount the diverter valve and dead legs or even leaks on the HW circuit, you would need to view the microswitch while the boiler is doing the phantom firing1

tony

 

[gas112]

Does he have xray eyes ? to see inside the switch then ?

 

[valcra]

it appears the diverter microswitch is new and was fitted with the new diverter.

after many attempts to observe microswitch operation it appears that it is working as it should and i can see and hear switch making and breaking when actuator moves in and out during a dhw demand.

actuator does not move nor do 2 switches when my combi "phantom" fires up.

any more suggestions on this problem gratefully accepted.

 

[valcra]

Is there any one interested in helping solve this problem??????

 

[Corgigrouch]

Where is the boiler located? does it have a frost stat fitted? Have you checked the timer for correct operation?

 

[Agile]

You have now confirmed that the phantom operation is NOT caused by a hot water demand or dead leg.

Next you need to see if a call for heat voltage is present when the phantom occurs.

I temporarily fit a mains neon lamp to the call for heat so that the customer can see if it lights during the phantom demand.

Tony

 

[valcra]

Where is the boiler located? does it have a frost stat fitted? Have you checked the timer for correct operation?

kitchen
no frost stat fitted
timer/programer is ok

 

[valcra]

You have now confirmed that the phantom operation is NOT caused by a hot water demand or dead leg.

Next you need to see if a call for heat voltage is present when the phantom occurs.

I temporarily fit a mains neon lamp to the call for heat so that the customer can see if it lights during the phantom demand.

Tony

room thermostat operating as it should, phantom demand occurs when room stat at off position.
small red light on programer does not come on during phantom demand.

 

[valcra]

To all who contributed to this thread.

Finally found the culprit

It was a tempremental pump overrun thermostat that caused the "phantom firing"

Removed and replaced with new. "no more weiredness"

Thanks to all for contributions to the thread.

valcra