Has our plumber put us in danger?
- Thread starter vexation
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I see above as a plumbing issue rather than what the boiler change has done.
If the water level in the vent drops, it is because the vent is on the suction side of the pump. The F+E pipe will be on the positive side of the pump. When the pump runs, water is pulled down in the vent and pushed up the F+E pipe into the cistern. If the F+E pipe was indeed blocked, water in the vent would not dip (unless an air bubble in the system could absorb rise in pressure).
When pump stops, system water finds its own level. Water in the vent rushes up the vent, past the level of the water in the header tank to spurt out before settling at the same level as the header tank water
Positioning of the two pipes to the header tank, in relation to the pump, is incorrect. These pipes are influenced by the pump. I as a heating engineer would be looking at the plumbing runs to ensure pump is located in the correct position. It looks to me the system was originally a gravity HW system with pumped heating zone, which has been converted to fully pumped without plumbing alterations. Often (for gravity HW systems) the pump was fitted in the return from the rads, but with no mechanical force (like a pump) in the gravity loop, system functioned correctly. Be aware, feed and vents would have been connected to the system at or near the indirect coil (not influenced by pump)
When a gravity HW zone is converted to fully pumped, without remodelling the F+E and vent locations, pump over is often the result (in this case suction- same thing)
Visualise a feed connection on a boiler. Let the pipe plumbed to this connection have two tees fitted to it (max 150mm between tees). First tee (branch 22mm) is connected to the vent pipe, second tee (15 branch) connects to F+E pipe. Then comes the pump inlet. Such a pipe run will mean both vent and feed pipes are at the pressure, so even blocked feed pipe, will not result in pump over.
I suspect this problem has always been there but new boiler characteristics have brought to light an existent anomaly.
If the water level in the vent drops, it is because the vent is on the suction side of the pump. The F+E pipe will be on the positive side of the pump. When the pump runs, water is pulled down in the vent and pushed up the F+E pipe into the cistern. If the F+E pipe was indeed blocked, water in the vent would not dip (unless an air bubble in the system could absorb rise in pressure).
When pump stops, system water finds its own level. Water in the vent rushes up the vent, past the level of the water in the header tank to spurt out before settling at the same level as the header tank water
Positioning of the two pipes to the header tank, in relation to the pump, is incorrect. These pipes are influenced by the pump. I as a heating engineer would be looking at the plumbing runs to ensure pump is located in the correct position. It looks to me the system was originally a gravity HW system with pumped heating zone, which has been converted to fully pumped without plumbing alterations. Often (for gravity HW systems) the pump was fitted in the return from the rads, but with no mechanical force (like a pump) in the gravity loop, system functioned correctly. Be aware, feed and vents would have been connected to the system at or near the indirect coil (not influenced by pump)
When a gravity HW zone is converted to fully pumped, without remodelling the F+E and vent locations, pump over is often the result (in this case suction- same thing)
Visualise a feed connection on a boiler. Let the pipe plumbed to this connection have two tees fitted to it (max 150mm between tees). First tee (branch 22mm) is connected to the vent pipe, second tee (15 branch) connects to F+E pipe. Then comes the pump inlet. Such a pipe run will mean both vent and feed pipes are at the pressure, so even blocked feed pipe, will not result in pump over.
I suspect this problem has always been there but new boiler characteristics have brought to light an existent anomaly.
Still pumps over after all rad & HW circuit bled. The top of the vent goes up 700mm above the F&E level and the feed point into the bottom of the pump is 2900mm below the F&E level.
One extra bit of data - with the manual bypass fully open, it pumps over noticeably more vigorously than with it shut. Also, watching it do it, the water has plenty of lime scale in it - both dissolved and in flakes.
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What the regulars are doing is remote diagnosis. Unfortunately, one needs to be on site for confirmation and firm fix. Just because the boiler was fitted from new does not mean plumbing was correct. I regularly look at newbuild with boiler having silly faults.
I strongly suspect plumbing is incorrect. I have already mentioned that feed and vent pipes should be at equal pressure. Bypass manipulation should not result in pumpover (it is just a short between flow and return after the pump)
I strongly suspect plumbing is incorrect. I have already mentioned that feed and vent pipes should be at equal pressure. Bypass manipulation should not result in pumpover (it is just a short between flow and return after the pump)
How can you watch water and know whats dissolved in it?
Any flakes are most unlikely to be lime scale which is whitish!
I would expect that any dirt is primarily metal oxides!
In any case any visible particles indicate a serious contamination issue and the likelyhood of much pipe blockage.
I thought you had said that it had been power flushed. With noticeable flakes in it then it certainle has not been flushed in any way!
Tony
been there got the tee-shirt with this problem!!
my advise would be check that the pump has been fitted the right way. usually an arrow on the pump for direction of flow. the arrow should be pointing towards the 3 way valve. another thing would be to reduce pump speed. usually 3 speed levels with these pumps try the lowest setting first. the old pump may have been set at a slower speed to accomodate existing problems with pipework. ive had this problem a few times before when changing open vented boilers. complete headache for the plumber and customer. auto air vents def need to be fitted to the highest point in the airing cuboard! this is a must!!
Peering into the F&E tank with a 1,000,000cd halogen lamp can be quite revealing.
Of course I'm only guessing, but the water is milky white with white flakes - just like looking into a scaled-up kettle. Our water is chronic with lime here in Dorset. This is after the system was over-pumping and overflowing for a while so plenty of fresh water has been through I guess.Well I watched the power flush at every stage and the water was black. Now it's white. Not sure if that's an improvement or not
Glow Worm Ultimate 80FF
The pump does have the arrow pointing up to the 3-port. The previous pump was a GRUNDFOS UPS 15-60 and was set to the maximum speed all the time. That was 2100 RPM.
The new pump is a "Circulating Pumps ltd. CP63. This has lower RPM for each range, (1800 RPM max) but the corresponding power figures are actually a bit higher - so I'm guessing more torque?
There's two high points of course - one either side of the 3-port. At the moment there's just an auto valve on the HW side. But this seems useless as any air trapped when HW only is going stays in that circuit. only when both CH & HW are running does the air get out and collect in the rads.ive had this problem a few times before when changing open vented boilers. complete headache for the plumber and customer. auto air vents def need to be fitted to the highest point in the airing cuboard! this is a must!!
Reading back over the previous page this stood out to me:
Measured at 700mm - but is this enough? I don't know if it's unusual, but the F&E tank is a fair distance away from the airing cupboard: Directly above the pump are two large cold water storage tanks (put in because of our power-shower) and then, several meters away is the F&E. Both feed and vent go straight up from the pump then along horizontally until they reach the tank.
The horizontal run is at the same level as the bottom of the tank so there's not much head above it.
Measured at 700mm - but is this enough? I don't know if it's unusual, but the F&E tank is a fair distance away from the airing cupboard: Directly above the pump are two large cold water storage tanks (put in because of our power-shower) and then, several meters away is the F&E. Both feed and vent go straight up from the pump then along horizontally until they reach the tank.
The horizontal run is at the same level as the bottom of the tank so there's not much head above it.
Therein might lie the problem. Do both the cold feed and expansion pipe rise from where they enter the roof space to the feed cistern to enable any trapped air to vent out at the F&E end? It's possible you may have an airlock in the horizontal cold feed (or even both pipes) In carrying out the pipework mods near the pump it is possible the fitter may have pushed the pipes upward so creating a high point.
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