Ocean Alpha 240E - HW Cutting Out

[PlumbHelpPlease]

Hi - any suggestions appreciated:

Boiler fires up to supply hot water but after a little while it shuts down and water runs cold. It then restarts and this cycle continues - my wife goes mad in the shower - so please help!

Done already:
Adjusting front panel HW thermostat - no difference.
Replacing HW divertor value diaphragm (had drip from front of unit) - no difference.

 

[EliteHeat]

Try replacing the secondary heat exchanger = big difference!

 

[PlumbHelpPlease]

Why would replacing the heat exchanger stop the boiler shutting down?
The issue is that the boiler cuts out repeatedly. When it is fired up the water is plenty hot-enough - so the heat exchanger is doing its job fine.

 

[EliteHeat]

If you say so

 

[PlumbHelpPlease]

Can anyone help with reasons why they think the boiler is behaving as described. EliteHeat's response above is not helpful as it provides no explanation.

Thanks.

 

[ChrisR]

Do a search on "secondary heat exchanger"

 

[Rob]

do you not find you radiators heating up when hot water is drawn, very common problem with these usually because the HE is blocked

 

[avidfan]

//www.diynot.com/forums/viewtopic.php?t=63541&highlight=

Try your sensors first.

 

[PlumbHelpPlease]

Thanks for tip - replaced DWH temp sensor and normal service has been resumed.

*** Note: Other users of this site - read this trail and take note - people are prepared to make random suggestions - so take them with a pinch of salt especially before you spend any money!

 

[Agile]

You probably had a sensor which went open circuit when it became hot. That is not very common. They more often go open circuit.

Some people may make suggestions to you which turn out not to be the fault in your particular case, but they are only trying to be helpful.

Tony

 

[Debsta]

I have EXACTLY the same problem with my ocean alpha 240e. Can I ask how much it cost to replace these sensors and has it been fine since?

 

[Gasguru]

Just because it appears to be the same fault doesn't mean it is...fluctuating water temperatures can be due to a variety of reasons.

Contact Alpha, they may have a list of engineers familiar with your boiler. Just swapping random parts is not the route to repair.

 

[Agile]

You can quickly measure the resistance of the sensor.

On test you can replace the sensor with a fixed resistor (@ 3 p ) and then measure the sensor as the boiler heats up.

Only try that if you are competent !!!

As the sensor is a cheap part at under £20 its a cheap DIY try. But as Geoff says above there are all sorts of problems which can give similar symptoms.

In our local area we would charge £84 to diagnose the problem plus about £13 for a sensor IF that was the problem.

Tony