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- 13 Feb 2009
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System was installed in the late 90's and has been very reliable, excepting one motorised valve replacement and one pump replacement.
Recently the boiler has been cutting out and the reset switch used to restore function. Behaviour started in early November and has become more frequent over time, now occurring almost daily, often cutting out after only 30 mins.
System is open vented, S plan with feed and expansion tank in the loft, system serves a 2 bed bungalow with 8 radiators. Pump is positioned horizontally in the loft approx 3m from the boiler (wall mounted boiler located in kitchen). There is a 15mm bypass installed between flow and return in the loft, the bathroom radiator also appears to be a bypass (has a TRV on the return side and heats up on HW setting). Motorised valves open and close ok as HW and CH is demanded.
Noticed the feed and expansion tank was filthy, so suspended the ball valve and bailed it. Horrible black gunge and rusty jelly-like substance removed. Tank wiped clean and refilled.
With heating on, most radiators are cool at the bottom while piping hot at the top. Removed two and flushed with a hosepipe, some black silt removed but not a huge amount.
Also noticed a weeping auto air vent in the loft, have replaced this.
From reading many forum posts, possible root causes are: Failing pump, air in system, sludge in system - all of which mean water doesn't move through the boiler quick enough.
Used the thermocouple option on my multimeter to measure temperature of flow and return pipes located directly above boiler. Difference was 10-11 degrees, which from what I can gather is normal?
All radiators heat up rapidly, which leads me to believe the pump is fine. All radiators are bled. I do plan to remove and flush the remaining radiators as time permits, but noticed volume of black sludge wasn't significant. However, much of the flow and return piping is under floorboards, so guess sludge is more likely to lie there as it's the lowest point in the system?
Other than flushing out the sludge and adding chemical cleaners and inhibitor, are there any other actions I can take (excluding boiler fault finding)?
I'm looking to exhaust the laborious diy problem solving tasks external to the boiler - any advice along those lines much appreciated.
Recently the boiler has been cutting out and the reset switch used to restore function. Behaviour started in early November and has become more frequent over time, now occurring almost daily, often cutting out after only 30 mins.
System is open vented, S plan with feed and expansion tank in the loft, system serves a 2 bed bungalow with 8 radiators. Pump is positioned horizontally in the loft approx 3m from the boiler (wall mounted boiler located in kitchen). There is a 15mm bypass installed between flow and return in the loft, the bathroom radiator also appears to be a bypass (has a TRV on the return side and heats up on HW setting). Motorised valves open and close ok as HW and CH is demanded.
Noticed the feed and expansion tank was filthy, so suspended the ball valve and bailed it. Horrible black gunge and rusty jelly-like substance removed. Tank wiped clean and refilled.
With heating on, most radiators are cool at the bottom while piping hot at the top. Removed two and flushed with a hosepipe, some black silt removed but not a huge amount.
Also noticed a weeping auto air vent in the loft, have replaced this.
From reading many forum posts, possible root causes are: Failing pump, air in system, sludge in system - all of which mean water doesn't move through the boiler quick enough.
Used the thermocouple option on my multimeter to measure temperature of flow and return pipes located directly above boiler. Difference was 10-11 degrees, which from what I can gather is normal?
All radiators heat up rapidly, which leads me to believe the pump is fine. All radiators are bled. I do plan to remove and flush the remaining radiators as time permits, but noticed volume of black sludge wasn't significant. However, much of the flow and return piping is under floorboards, so guess sludge is more likely to lie there as it's the lowest point in the system?
Other than flushing out the sludge and adding chemical cleaners and inhibitor, are there any other actions I can take (excluding boiler fault finding)?
I'm looking to exhaust the laborious diy problem solving tasks external to the boiler - any advice along those lines much appreciated.
