nice one felix i did the same / you must think quicker
he could always close the gate valve temp that will prove it
he could always close the gate valve temp that will prove it
Perplexing heating / water problem
- Thread starter RedAl
- Start date
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You keeping the pups in line now d.i.a icon_twisted.gif
Trying curlydon, very very trying
I need to think some more first, in the meantime go to the header tank with a glass of water and while you hold it under the vent pipe get some one to turn the boiler on
Does it take the water out the glass.
Trying curlydon, very very trying
I need to think some more first, in the meantime go to the header tank with a glass of water and while you hold it under the vent pipe get some one to turn the boiler on
Does it take the water out the glass.
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cant see it d.i.a it was pumping over at first post
kevplumb said:cant see it d.i.a it was pumping over at first post
A good point well spotted kev.
Open vent in the line of least resistance the top of boiler.
Pump in the worse possible position sucking out from the least line of resistance, the top of the boiler, and also pumping down the worse possible orentation.
S plan with no by-pass sucking water from the top of the boiler.
No mention of loads of air in the system yet.
An enlighten guess at this stage would be the pump not working in one or the other zones, causing the vent to blow over because the boiler is overheating.
Second guess is something has been added or removed to/from the system incorrectly thats causing a short circuit.
From the pics the system is a typical diy mess, and i will need to ask lots more questions yet.
Tell us as much as you know about the system please.
tommorow i have din dins with the boys in crickelwood so till thurday goodnight
From the pics the system is a typical diy mess, and i will need to ask lots more questions yet.
Tell us as much as you know about the system please.
tommorow i have din dins with the boys in crickelwood so till thurday goodnight
An overheating boiler filling the vent with steam bubbles is a common cause of water pouring from a vent pipe. Unfortunately, it doesn't tie in with the fact that the problem increases with flow rate.
Here's a simple test. Turn off the boiler gas valve and pump cold water round the system. My guess is that water will still pour from that vent. Until I'm proved wrong, my money's on Bernoulli's equation.
Here's a simple test. Turn off the boiler gas valve and pump cold water round the system. My guess is that water will still pour from that vent. Until I'm proved wrong, my money's on Bernoulli's equation.
Blimey, it looks like you're all as perplexed as I am.
The house is a converted farm building. It was converted 10 years ago which would be when the heating was installed. As far as I know no adaptions / alterations have been made since.
We moved into the house in November. The radiators have been full of air and gurgling away since we moved in.
The second sign of trouble was a damp patch on the ceiling which led to the investigation of the loftspace to find huge amounts of condensation caused by a tank full of hot water.
The one bit of the system that is reall hard to get access to is the f/e tank.
Most of the house is single storey with just one upstairs room. The f/e tank is in the loftspace above the single storey part. So to get the necessary height above the highest radiator the tank is right up in the rafters of the loft and impossible to see into.
Thanks for your help so far fellas.
The house is a converted farm building. It was converted 10 years ago which would be when the heating was installed. As far as I know no adaptions / alterations have been made since.
We moved into the house in November. The radiators have been full of air and gurgling away since we moved in.
The second sign of trouble was a damp patch on the ceiling which led to the investigation of the loftspace to find huge amounts of condensation caused by a tank full of hot water.
The one bit of the system that is reall hard to get access to is the f/e tank.
Most of the house is single storey with just one upstairs room. The f/e tank is in the loftspace above the single storey part. So to get the necessary height above the highest radiator the tank is right up in the rafters of the loft and impossible to see into.
Thanks for your help so far fellas.
We moved into the house in November. The radiators have been full of air and gurgling away since we moved in.
you have bled them
you have bled them
So what happened when you temporarily closed the gatevalve on the cold feed with everything hot and pumping? Did the pump-over slow down? or stop?
And the condition of the pump isolator on the suction (top) side of the pump also suggests a potential air leak.
And the condition of the pump isolator on the suction (top) side of the pump also suggests a potential air leak.
I have the answer.............
Rip the lot out and fit a combi
Rip the lot out and fit a combi
dia said:
"Pump in the worse possible position sucking out from the least line of resistance, the top of the boiler, "
but it isn't, it's pumping towards the boiler.
This is a problem I've seen half a dozen times, surprised nobody else has come across it. (One result of it is that you get reversed flow in combi boiler's radiator circuits when they're providing hot water, cos the diverter valves let-by a tiny bit.)
Felix is right but does he know why!
It isn't a venturi, as we look at the pipes. You only get a venturi, and the suction effect, where there's a big reduction in the diameter of the pipe. We have no reduction?? No reduction means no suction. There is a reduction in the sense that the size of the pipe 22mm? is smaller than the size of the boiler, which is where the vent goes off. If you do your Bernoulli sums you'll find the difference. I doubt it will be huge because the pipe is fairly large compared to the boiler - I'll work it out when I have some time. There will be a difference, though the set-up is common enough and we would see it more often if it were large.
Except that there is a venturi. A magnet will confirm that there's a build-up inside the pipe, of scale containing magnetite, at the point where the feed pipe joins the return. THAT is what has caused the reduction in diameter and resultant venturi effect. Berni's figures wouldn't be accurate here because of flow separation, which is to do with the real situation of the flow at the side of a pipe being much slower than in the middle, and the more important dramatic effects caused by turbulence where you dont get laminar flow. The effects due to turbulence can outweigh the effect of pipe diameter by a large factor.
It's made worse by the fact that the vent pipe rises very little above the level of water in the f/e tank. It would be better in this case if the vent pipe were larger in diameter in the length where the water level is because it would then rise less.
The scale will have been building rapidly once pump-over started, as that leads to introduction of air therefore oxygen into the water.
Solution may well be to drain down, cut the pipes and have a butcher's. It's common to find that replacing the adjacent pipes is easier than cleaning them. When you put them back it would be good to make the feed pipe come in from underneath, ie with bends, so that you don't get convection currents mixing the hot and cold (airy) water much. Of course you could always put a fat bit of pipe in there to tee off!
http://home.earthlink.net/~mmc1919/venturi.html
"Pump in the worse possible position sucking out from the least line of resistance, the top of the boiler, "
but it isn't, it's pumping towards the boiler.
This is a problem I've seen half a dozen times, surprised nobody else has come across it. (One result of it is that you get reversed flow in combi boiler's radiator circuits when they're providing hot water, cos the diverter valves let-by a tiny bit.)
Felix is right but does he know why!
It isn't a venturi, as we look at the pipes. You only get a venturi, and the suction effect, where there's a big reduction in the diameter of the pipe. We have no reduction?? No reduction means no suction. There is a reduction in the sense that the size of the pipe 22mm? is smaller than the size of the boiler, which is where the vent goes off. If you do your Bernoulli sums you'll find the difference. I doubt it will be huge because the pipe is fairly large compared to the boiler - I'll work it out when I have some time. There will be a difference, though the set-up is common enough and we would see it more often if it were large.
Except that there is a venturi. A magnet will confirm that there's a build-up inside the pipe, of scale containing magnetite, at the point where the feed pipe joins the return. THAT is what has caused the reduction in diameter and resultant venturi effect. Berni's figures wouldn't be accurate here because of flow separation, which is to do with the real situation of the flow at the side of a pipe being much slower than in the middle, and the more important dramatic effects caused by turbulence where you dont get laminar flow. The effects due to turbulence can outweigh the effect of pipe diameter by a large factor.
It's made worse by the fact that the vent pipe rises very little above the level of water in the f/e tank. It would be better in this case if the vent pipe were larger in diameter in the length where the water level is because it would then rise less.
The scale will have been building rapidly once pump-over started, as that leads to introduction of air therefore oxygen into the water.
Solution may well be to drain down, cut the pipes and have a butcher's. It's common to find that replacing the adjacent pipes is easier than cleaning them. When you put them back it would be good to make the feed pipe come in from underneath, ie with bends, so that you don't get convection currents mixing the hot and cold (airy) water much. Of course you could always put a fat bit of pipe in there to tee off!
http://home.earthlink.net/~mmc1919/venturi.html
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