Poor flow in C&M Britony Combi boiler

[nickgray]

I have a Chaffeatux & Maury 'Britony' Combi boiler which is less than two years old but isn't too happy. It won't fire, and following the diagnosis chart, it looks like there is insufficient flow in the heat exchanger. Could this have scaled up or sludged-up within two years. Don't know if its got Furnox in from installation or not.

Is it worth checking the filter is clean ? Could these block up enough to prevent enought flow ? Is is a permanent part which I just rinse out, or do I need to replace it with a new one ?

Should I descale by adding some of that Furnox system cleaner (in the tube) and getting it circulating ? Or just remove the exchanger and clean it in some hot descaler in the kitchen sink ?

Any other experiences/advice about this model would be welcome.

 

[oilman]

Which heat exchanger?
Do you have good flow from the hot tap?
Does the boiler work at all?

 

[nickgray]

The boiler was working ok last night !
The pump works, and as far as I can tell the various sensors work ok. Since neither the HW nor the CH work I guess that if it is a flow problem which the boiler is detecting, its the primary heat exchanger.
I drained the boiler (not the whole system) and the water was quite muddy. I flushed it until the water was clear, but its still not working.
Flow is OK through the taps (upstairs and kitchen just next to the boiler), haven't had any problems with mains water pressure either (although this time of year it should be fine in most places).

 

[nickgray]

any ideas - anyone ?
Will the pump (grundfos 15-50) be unhappy if I reverse the flow through it when flushing it out ?
Will the fernox cleaners clean out any dregs in the pump ?