Ferroli boiler fault dignosis

[jeremyf71]

I have a 10 year old Ferroli 701. The circuit board was replaced 9 months ago.
The problem I have is the hot water cuts out momentarily at the taps while the demand light is still on. When watching the boiler flames after a minute or so, they appear to drop as if the gas valve is modulating for low demand (which hasn’t changed and is on full). At this point the gas is either cut for 10 seconds before being ignited again or it just rights itself for a random amount of time before doing it again – this is all with the demand light on.

I’m guessing it’s difficult to diagnose from this description but what other information do you require.

PS it may be relevant but I have previously had problems with the CH coming on if the temp setting is low. When cold, there appears to be a delay between the point where gas valve is open and actual ignition – this can be smelt outside near the flue. If I turn the heat setting higher, it seems to ignite quicker.

Where do I start with diagnosis – would simple tests on temp sensor/flow sensor be a good start? What factors modulate the gas valve?

Many thanks

Jeremy

 

[Agile]

Anyone fitting a new PCB should have checked and adjusted the gas settings.

The boiler uses sensors to measure the temperature and adjust the gas flame accordingly.

That effect can occur if the part which transfers heat into the hot water is dirty or scaled up.

Be aware your boiler is getting pretty old!

As gas settings may be involved my advice is to get a competent engineer but make sure you call sosmeone who repairs boilers and is not just going to come and tell you that you need a new one.

Tony

 

[jeremyf71]

Many thanks. I have been told a few times its getting old - is this a sefety issue or an economic issue?

I fitted the board with advice that nothing needs to be adjusted - I'm guessing that was incorrect information?

Is there a way to work out if the temp/flow sensors are reading incorrectly before moving on to possible blockages in the heat exchanger?

It will be serviced early next year. Should any gas setting be adjusted as a matter of course during a service?

thanks again

Jeremy

 

[Agile]

I dont remember if there are gas settings on the PCB, but its quite likely.

However, thats not the point! When any major work is done on a boiler the gas settings should always be checked to ensure they are correct. They can drift over time and the last 701 that I saw had drifted quite a long way!

They should also be checked on a service but unfortunately I would say that whilst many would check the maximum, very few would check the minimum.

Providing your boiler has been properly serviced and is operating correctly then its perfectly safe and they are pretty reliable too. But at that age can be getting a few faults occuring and many engineers will not want to repair it but just quote for a new one. They are still quite repairable though.

You can measure the sensor resistance when totally cold but they are unlikely to be at fault but could be and the fault may not be identifyable when cold either.

Tony