Potterton Prima B Noise, Powerflush needed?

[cjp2k]

Hi guys, my Potterton Prima 40b Open Vent has started making a droning noise, this only started after British Gas did their annual service (The guy seemed to have problems putting the bits back inside the boiler... could that cause the noise?) It only happens after about 30minutes and is intermittent when the boiler fires, when the pumps running and the boiler has stopped heating, the noise stops...

Anyway they came back and replaced the pump head as it could be the bearing (which hasn't fixed the problem) they now said its sludge as the system is "incredibly dirty"

The pump (Grundfos) is above the boiler, when he opened up the drain the water was clear, when he removed the pump head black water came out, the system has Fernox F1 in the system, and the radiators get "bouncing hot" all over with no cold spots as British gas engineers describe it,

The engineer was very quick to quote the £800 flush and offer me finance on it, to a point he had his phone out to ring to arrange the credit!

My question is do most pumps have a bit of black water in the bottom of them, (the pump was approx. 20 years old) or is my system knackered as British Gas would like me to believe

 

[Agile]

The engineers get a small commission if they get you to have their power flush or even a quotation visit for a new boiler.

Pumps turn by magnetism and that attracts magnetic dirt from the circulating water.

I would doubt that your system has enough dirt to warrant power flushing which by an independent is about £350.

A lesser but adequate treatment would usually be to fit a magnetic filter and add a cleaning chemical to loosen the dirt.

I have not heard the noise, but it could be a form of kettling which is common on an old cast iron heat exchanger like yours. That can be treated by adding Sentinel X200 which can be left in the system.

Be aware that your boiler is quite old and overdue for replacement. But it is very reliable however a new one would save about 25% of the gas consumption.

Tony Glazier

 

[cjp2k]

Thanks will try the x200. The noise gets louder when I turn the pump down

Also currently Looking at a new intergas or Worcester boiler