Blocked heat exchanger - remove boiler to clean?

[matz]

we have one of these boilers and when boiler is set to continuous and you click the room stat up then click it back again after 5 secs before the boiler fires, the pump runs for 5 minutes on its own....

 

[mogget]

Indeed, you could set the pump overrun to maximum first too. But I would turn the gas off first. I stand by not running it in reverse as a bidirectional boiler would probably be a selling point for the manufacturers.

 

[C.J]

Thanks mogget and matz, I think I'll re dose with x800 and leave it in for a while, maybe a few weeks and see if it gets better over time, if not then I will try reversing the pump and rig some power to it so it can be left running in reverse for a few hours

 

[mogget]

At this time of year you could downrate the boiler so that there's less film boiling trying to bake the dirt on at the same time as the x800 is trying to dissolve it.

I don't know how big your house is but you could start at 8-10kw and go from there. I'd say to lower the flow temperature if you can to about 60deg too, but depending on how much hot water you use it could get expensive heating the cylinder with electricity (assumption: you have a working immersion heater).

KW output is in d.0 iirc. It's easily user-adjustable on the 400 series.

 

[C.J]

Thanks, I'll have a read on how to lower the output, and yes I have a working immersion heater
Cheers