how to check heat exchanger

[we88ie]

I think my heat exchanger is defective

My pressure in combi boiler remains quite stable but it leaks from the safety valve when the heating is on. When the heating is off the leak is barely noticable.

The pressure does rise slighty but I've never seen it get to 3 bar to activate the safety.

The wierd thing is I dont have to ever add any water

I've disconnected the filling loop so I know the filling valve isnt passing and letting water into the system.
The expansion vessel has been recharged to 1 bar and holds presure fine.
I've replaced all the diapragms, etc from a new service kit.

So I reckon there must be a leak in the heat exchanger allowing a small amount of tap water into the central heating circuit which in turn is leaking off through my leaky SRV.

Is there a way to test the heat exchanger without dismantling the boiler and should I buy a Vokera spare part or a pattern part at half the price at the same time I get a new SRV ?

I've stripped and cleaned the SRV but did read in here that once they let water through then it's best to replace them.

thanks

Webbie

ps: I remember a long time ago when filling the bathroom sink in the morning that sometimes there were small black paticles in the water. I havent seen them now for ages but could this have been a sign that the heat exchanger had failed

it's a Vokera Linea 28 (7 year old)

 

[croydoncorgi]

If you can stop the PRV leaking, it's easy to test the secondary HX.
Just set the pressure to 1.5, turn off the cold supply under the boiler and run the heating for a while. If the pressure doesn't change, the problem is a leak between the two halves of the 2ndary HX - reasonably cheap and easy to fix.

There's nothing to choose between pattern PRVs and 'genuine' parts - you're just contributing to the profit of another link in the supply chain - so long as it fits and is set to release at 3 Bar.

 

[Paul Barker]

Shut the black tap knob faciung you on the right underside of the boiler to test it. This will prove it unless you have a mixer tap with no check valves in, because they will back feed the heat exchanger through the hot.

If it isn't this the filling loop is letting bye. The way to test that is undo tjhe flexible connector. In anycase it shouldn't be permanently connected.

 

[we88ie]

thanks for the replies and the help guyz

Heat Exchanger and New SRV on order

wish me luck

Webbie

 

[we88ie]

Heat Exchanger replaced

really easy job to do, just undo 2 screws and slide it out.

boiler doesnt fill up on it's own now, pressure stays the same and SRV doesnt leak.

thanks for all the help

Webbie