Ravenheat RSF 820/20 Central Heating Issue

[Poisonata]

I have a Ravenheat RSF 820/20 combi boiler (15+ years old) which has developed a problem. I was made only aware of it today as it's the first day I have felt the need to switch on the central heating.

It has and still is functioning fine when it comes to hot water however select central heating, the light comes on to indicate it central heating has been switched on but thats it. Nothing happens. No noise, no clicks, nothing (The 'hot water only' switch is correctly set to 'hot water/central heating' ).

I am fairly adept at changing parts in the boiler, what I lack is the skills to diagnose the problem.

If anyone could post a check list of ideas I could work my way through would be much appreciated. I will check this post periodically incase I have neglected to mention information required for the diagnosis.

Many thanks in advance.

 

[kevplumb]

this might help

View media item 15368
you will have to save it and blow it up or press ctrl +

 

[Poisonata]

Thank you for that, very helpful.

I was wondering if it might be the pump. Any advice on a quick way to check if the pump is not working. I don't have the facility to check the voltage as the flow diagram suggests.

 

[kevplumb]

View media item 667
undo the screw marked bleed hold a cloth under as you will lose a tad of water

you can spin the shaft with a narrow screwdriver if its running you will see it if the boiler is on

 

[Agile]

It sounds very likely to be the pump as this boiler can give hot water with the pump jammed like the Puma.

Tony

 

[kevplumb]

It sounds very likely to be the pump as this boiler can give hot water with the pump jammed like the Puma.

Tony

and the old sauniers

and haven't we all been there

 

[Poisonata]

Thank you both for replying.

I'm fairly confident myself it's the pump. I know the pump is at least 12 years old (not sure how long they are designed to last).

One final thing please (more for my interest). Is there some sort of flow valve or detector that tells the boiler the pump hasn't kicked in and not to fire up.

Thanks both once again for being so helpful. Very much appreciated.

 

[Agile]

Pumps can last for 30-40 years on a clean system.

A week if lucky on a dirty system !

Boilers are simple and cheap masss produced appliances in a competitive market place. They cannot afford to included sensing devices which dont contribute to the output.

The boiler engineer is called if something does not work correctly.

Having said that the Vaillants do a very good job of diagnosing possible problems from an assessment of the very few parameters they do measure.

Tony