Alpha CB28 central heating fine, intermittent hot water

[sam40]

Where to start...so boiler losing pressure daily but simply repressurised it, then two days ago stops completely, no heating, no water.

Had new pressure relief valve fitted and now have CH but intemittent hot water...goes hot then cold then tepid etc etc.

Would love to know if anyone has any ideas and if it is worth constantly repairing this boiler?

Many thanks
Sam

 

[meldrew's_mate]

Sam, the first thing to do is cure the leak which causes the pressure to drop.

The other symptom points towards a failed diaphragm in the diverter valve, but could also be an indication that the secondary heat exchanger is partially blocked,

When hot water tap is on full what rate does the water flow at (gals or litres per minute)? Measure it with a bucket and stopwatch.

When at full hot water flow, does the burner cycle ON-OFF-ON, etc.?

At partial flows of about 3 litres per minute, does the boiler fire?

 

[sam40]

Thanks Meldrew's mate, the leak appears to have been solved. Latest news....At low flow rates the hot water gets really hot and then the boiler cuts out with red light on constant. What does this point to?

 

[ChrisR]

Very blocked secondary heat exchanger?
What colour are the temp sensors?

 

[sam40]

Hi Chris,

When the boiler cuts out there is a constant red light on A and a flashing amber light on B.

Currently there is heating in the CH but not very hot, rads tepid. Water still cycling tepid/cold

Some Fernox was put into system to try to clean any potential blockages- how long should this take?
Thanks

 

[Humph]

Sam ,cant help you with problem but i also have an alpha boiler and when i had an issue with it a couple of years ago i found there helpdesk very good.I took out a cover that costs £12 a month and covers boiler 365 days a year and you get a yearly service.Might be worth giving them a call.
Good luck.

 

[ChrisR]

5. INDICATOR NEONS
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 - Burner is alight.
B Flashing on and off - Temperature sensor fault, contact your Service Engineer.
A Flashing on and off - Overheat thermostat has operated. Rotate selector switch to the reset position (3) to reset. If this continues
to happen, contact yor Service Engineer.
A Illuminated continuously - Burner has failed to light. Rotate 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, contact your Service Engineer.
A and B Flashing on and off alternatively - System pressure is very low and re-pressurisation is required.

What colour are the temp sensors?