Alpha CB28X - random turn on of CH

[coopersim]

I have a friend with an Alpha CB28X Combi boiler, during the summer months she turns the switch on the mechanical rotary timer in to the off position - therefore, you would assume that the CH is totally off, however, at random intervals (not dependant on the time of day) the central heating will turn on, heat up for a few minutes, then turn off again. This has been noticed in the morning and the evening.

Could this be a faulty timer? Or maybe a faulty frost stat?

Several people have pondered, any ideas please?

Thanks,

Simon.

 

[kevplumb]

hot water flow switch sticking springs to mind

 

[coopersim]

hot water flow switch sticking springs to mind

Would this only be the case if there were demand for hot water from a tap though?

 

[doitall]

the Alpha cb28x has a daily pump run to prevent it sticking.

 

[ChrisR]

Sure like most combis, but usually they don't LIGHT!

 

[doitall]

This is true Chris it's the steamy ones that do that.

Micro switch on the divertor valve is worn or sticking or Hot water flow switch.

Best bet is to change the flow switch.

 

[kevplumb]

This is true Chris it's the steamy ones that do that.

Micro switch on the divertor valve is worn or sticking or Hot water flow switch.

Best bet is to change the flow switch.

fink i i was there

 

[doitall]

fink i i was there

Lucky guess

 

[kevplumb]

88llocks m8

 

[coopersim]

sorry to keep on coming back to this same point, but is this still the case if there is no CH & no HW demand?

I thought that the divertor valve / HW flow swtich would only be active when there is demand for HW/CH, in this case, there is neither!

 

[doitall]

sorry to keep on coming back to this same point, but is this still the case if there is no CH & no HW demand?

I thought that the divertor valve / HW flow swtich would only be active when there is demand for HW/CH, in this case, there is neither!

The flow switch is part of the divertor valve. if its not shutting off properly the boiler will fire in the daily kick to prevent the pump sticking.

The pump is designed to run for a few minutes every 24 hours.