Potterton Suprima 80 - open system

[ricksalmon]

I'd be grateful for any opinions anyone has on the following problems:-

Potterton Suprima 80 - open system about 9 radiators over a three bedroom flat.

One cold radiator at far end of system - system bled regularly (almost daily at the moment).
Whole system power flushed about six weeks ago (lots of sludge came out). Then the cold radiator removed and cleaned out (lot of sludge still in that radiator).

Boiler continually going into lockout - (sometimes many times a day).
When the pump is set at three the lockout problem is worse the boiler makes alot of knocking noises and the system pumps lots of water into the header tank which then vents water out of the overflow. However some heat does seem to get to the base of the cold radiator.
Pump at two fewer lockouts and less overflow issues no heat to back radiator.
When the pump is set at one the lockout problem is reduced but no hot water reaches the cold radiator and no overflow.

The boiler was serviced about 20 months ago and heat exchanger changed I am not sure if the PCB was changed but the one there is the modern one with the square button reset.

Any thoughts appreciated as me and several plumbers seem to be stumped by these problems.

Thanks

Rick

 

[lightning]

Cold feed blocked ,needs cutting out and replacing, power-flushing will not remove blockage from there.

You are getting pumping over where boiler flow is coming out of your f/e vent pipe due to blocked cold feed

 

[ricksalmon]

Do you mean the cold feed to the header tank which is controlled by a tap and is delivering cold water to the header tank.

 

[lightning]

//www.diynot.com/forums/viewtopic.php?t=37170&sid=b84cd694bade6ef2d836c75c24d357f5

Scroll down till you get to pump over

 

[ricksalmon]

OK

Thanks Lightning

So the likely blockage is where the feed from the header tank joins onto the system.

I'll give this a go

Thanks again