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dneale123
Hi,
Newbie here and long story so please go easy :smiley2:
Hoping to keep our ancient heating system going for a while longer without too much work (boiler replacement, probably change to combi, planned for the spring, just trying to avoid major plumbing work while the weather's cold if possible).
Our system has a bit of a history of pumping over into the F&E tank in the loft when hot. Originally with the old Wilo pump this only happened on the maximum (3) setting and turning it down to 2 cured the problem. The system dates from about 1980 and is very primitive, with 6 rads and a hot water cylinder apparently just plumbed in parallel with no diverter valves. There are TRVs on the rads but no scope for adding a system thermostat without extensive work (see below for reasons).
The pump eventually failed 2 years ago and was replaced by a basic Primaflow unit that looks like it could be a rebadged Grundfos. Problem is that this pump has got noisy and has started to struggle to circulate water at the 1 setting but works happily and quietly at 2, but after about 1.5 hours the pump over starts. I've tried opening all TRVs fully and reducing the boiler temperature setting (ancient Potterton Flamingo 20-30) but this makes no difference. All rads and hot water get hot and the boiler thermostat is working fine (the hot water is always very hot, of course!).
The system is configured with the pump pumping upwards in the flow feed, followed by a horizontal run with the vent and cold feed from the F&E tank (I think they're in the flow - it's hard to trace under the floorboards). I'm aware this isn't an ideal arrangement, but am trying to avoid replumbing as the system was kindly installed with all the important plumbing under the floorboards under the hot water cylinder - so I would have to demolish the airing cupboard or take a ceiling down to get access!
I've flushed the system through a couple of times in the last few days and the water is running clear (a small amount of black sludge came out but the water was mostly clear, and I de-sludged the system about 5 years ago when the bottom of the downstairs rads was getting a bit cool and this helped at the time). All rads have been taken off in the last few years and flushed, and the system has always had inhibitor in it. I've also inspected the F&E tank and this looks OK - the water in it is clear and the top of the vent is about 450mm above the water level. The tank was a bit full (just over half full when cold) so I've bent the ball cock arm a bit and it now fills to about 100mm when cold.
For now I've put some X400 in and plan to run it for a week or two to see if it helps. Apart from perhaps bashing the pipework and rads occasionally is there anything else I can easily do without demolition work? Or is the best thing to leave the system limp on (at the moment I'm running the heating+HW 3 times a day for 1.5 hours to minimise pump over) until boiler replacement in the spring, given that replumbing under the airing cupboard is very awkward? And is there a particular reason why the pump over only happens when the system is hot, even with the radiator valves fully open?
TIA!
David.
Newbie here and long story so please go easy :smiley2:
Hoping to keep our ancient heating system going for a while longer without too much work (boiler replacement, probably change to combi, planned for the spring, just trying to avoid major plumbing work while the weather's cold if possible).
Our system has a bit of a history of pumping over into the F&E tank in the loft when hot. Originally with the old Wilo pump this only happened on the maximum (3) setting and turning it down to 2 cured the problem. The system dates from about 1980 and is very primitive, with 6 rads and a hot water cylinder apparently just plumbed in parallel with no diverter valves. There are TRVs on the rads but no scope for adding a system thermostat without extensive work (see below for reasons).
The pump eventually failed 2 years ago and was replaced by a basic Primaflow unit that looks like it could be a rebadged Grundfos. Problem is that this pump has got noisy and has started to struggle to circulate water at the 1 setting but works happily and quietly at 2, but after about 1.5 hours the pump over starts. I've tried opening all TRVs fully and reducing the boiler temperature setting (ancient Potterton Flamingo 20-30) but this makes no difference. All rads and hot water get hot and the boiler thermostat is working fine (the hot water is always very hot, of course!).
The system is configured with the pump pumping upwards in the flow feed, followed by a horizontal run with the vent and cold feed from the F&E tank (I think they're in the flow - it's hard to trace under the floorboards). I'm aware this isn't an ideal arrangement, but am trying to avoid replumbing as the system was kindly installed with all the important plumbing under the floorboards under the hot water cylinder - so I would have to demolish the airing cupboard or take a ceiling down to get access!
I've flushed the system through a couple of times in the last few days and the water is running clear (a small amount of black sludge came out but the water was mostly clear, and I de-sludged the system about 5 years ago when the bottom of the downstairs rads was getting a bit cool and this helped at the time). All rads have been taken off in the last few years and flushed, and the system has always had inhibitor in it. I've also inspected the F&E tank and this looks OK - the water in it is clear and the top of the vent is about 450mm above the water level. The tank was a bit full (just over half full when cold) so I've bent the ball cock arm a bit and it now fills to about 100mm when cold.
For now I've put some X400 in and plan to run it for a week or two to see if it helps. Apart from perhaps bashing the pipework and rads occasionally is there anything else I can easily do without demolition work? Or is the best thing to leave the system limp on (at the moment I'm running the heating+HW 3 times a day for 1.5 hours to minimise pump over) until boiler replacement in the spring, given that replumbing under the airing cupboard is very awkward? And is there a particular reason why the pump over only happens when the system is hot, even with the radiator valves fully open?
TIA!
David.
If that's the case maybe a plunger will shift it? (I've just prodded it with a length of coathanger but don't think I'll be that lucky!)
