Alpha CB28 does it again. Aaaagggghhhh!

[Slime]

Hi all & belated season's greetings.
This is a red light problem in that it intermittently comes on and I get cold water and no heating. There is no consistancy with this issue.
It may be fine for many days and then the light comes on and I have to reset the boiler. Sometimes three or four times before the boiler fires up, sometimes only once. It may then be okay for a week or so, or may be just a day!
Once or twice the red light has been flashing, but, 95% of the time the red light is solid.
I've searched the internet but can't seem to find a finite answer.........maybe there isn't one. My overriding hope is that there's an Alpha engineer lurking on the forum with an answer that doesn't involve over large sums of money!
All the best & many thanks,

Slime.

 

[45yearsagasman]

If the red light A is lit continuously, it usually indicates a failure to light.
If it flashes then its usually an overheat condition. I'm assuming that the yellow B light remains off, as you make no mention of it. Either way, I would not recommend diy attempts at repairs, and get a pro in to check it out. It may only require a service and resetting.

 

[petertheplumber12]

When neon A (red) and neon B (yellow) are illuminated, the following conditions apply:-
Neon
B Flashing very slowly (every 5 seconds) - Electricity supply to the boiler is on.
B Illuminated continuously - Indicates the burner is alight.
B Flashing on and off - Temperature sensor fault.
A Flashing on and off - Overheat thermostat has operated. Rotate selector switch to the reset position (3) to reset.
A Illuminated continuously - Burner has failed to light. Rotate the selector switch to the reset position (3) and the
ignition sequence will restart after a delay of about 30 seconds.
A and B Flashing on and off at the same time - Blocked flue or fan fault.
A and B Flashing on and off alternatively - System pressure is very low and re-pressurisation is required.
Hope this helps with identifying,

 

[ianmcd]

OP in order to supply you with the correct information we need to know exactly what both lights show when your boiler locks out, I suspect you will have

A Illuminated continuously and B flashing

Come back on and let us know what BOTH LEDs are doing and we can give you more information

 

[Slime]

OP in order to supply you with the correct information we need to know exactly what both lights show when your boiler locks out, I suspect you will have

A Illuminated continuously and B flashing

Come back on and let us know what BOTH LEDs are doing and we can give you more information

The red light is on constantly, (99% of the time & 1% of the time it was flashing), and the yellow light is not on at all until after a successful reset.
I hope this helps,

Slime.

 

[bolshy]

I fixed one of these yesterday. The yellow neon (B) will flash every 5 seconds when the boiler has power to it with no demand for heating or water. It stays on when the burner has lit, and MAY flash when there is a sensor fault.
A constant red neon (A) will usually indicate a flame failure - the boiler has failed to ignite and has locked out. There could be several reasons for this.
These neon indicators are only a crude fault finding aid - the CB28 I repaired yesterday was cycling erratically and the neons were lighting erratically too. A defective sensor can give strange neon sequences. I'm led to believe the circuit board on these is pretty robust - you need someone who knows what they're doing to check the boiler out for you.

 

[bolshy]

Oh - and the Alpha CB28 manual is available online in PDF format.