Alpha CB28 -mainburner not firing.

[undercover]

Well its been a long day. Couple of services and repairs this morn then started an install this pm. On way home was asked to look at an Alpha CB28.

Not a boiler i am overly familiar with but went along. Both neons lit and for some strange reason the customer was draining a large saucepan of water from the downstairs radiator He thought the flashing neon meant he had to bleed air from the rad. Must have been 1-2 pints in the saucepan Anyway i repressurised, reset and tried to fire it up. Heard the fan, ignition proved with good spark but the main burner would not light. Boiler went into lockout.

Gas is there. checked fan with meter, and cleaned venturi, aps checked and ok, gas valve has 240v on PCB. Was late but am i missing something??


PS: Aahhh?? Does the pump have to be spinning on tjis model to also complete the sequence. Think i missed checking it

 

[ChrisR]

Yup, I often find the penny drops while I'm explaining a problem to my dear wife, who as you can imagine, is really interested.

 

[Dan Robinson]

hah not your bloring pipes again! Sergoi yado honnto ne!

Thats what I get most evenings Chris.... It the universal language of "bored spouse syndrone". Which soon changes when that invlolves being forced to shop at Liddels 'cos those boring pipes workid properly for a change .

 

[undercover]

at the end of one of those days where you think 'who am i' 'where am i' and 'whats this do'

Anyway, calling back tomorrow to check pump and PCB

 

[Dan Robinson]

I always know what it does, it's more a case of where I can do it

 

[Paul Barker]

There is no primary flow switch, the pump is proved after ignition by the rate of temperature rise of the thermisters, mainly primary.

If the burner never lights it isn't the pump.

The fan sequence is fan starts then stops then starts again, boiler goes to ignition and allows gas in simultaneously after fan is restarted.

If there is never any flame you have a problem with gas, whether that be modureg or signal from pcb or main gas solenoid or stachel thrown in cupboard under stairs knocked ecv off..

pcb on this model are more or less bullet proof I've never needed one so don't be tempted to buy one.

Would be useful to know the light behaviour after failure. Red light A continuous after fualt is unhelpfully telling you burner failed to light.

B flashing faster than every 5 seconds thermister

A continuous B flashing pump (but more likely to be thermister)