R
rickphysicist
I am not a plumber but have been called in by my son whose plumbers have failed to solve a problem which sounds much like this. The boiler effectively shuts down through water starvation.
I notice two irregularities on the installation - Vaillant vented ecotech plus (inst. guide). One, the pump is in the return pipe before the boiler and drives through a raised loop with no bleed, Two, the feed and vent are within 150mm in the flow circuit but the wrong way round.
Number one exacerbates the problem but I am sure when we swap them round two will be the real cause.
When air/water mix flows down the flow circuit, the first opportunity the air gets to escape is the water feed pipe (15mm). It takes it, the bubbles expand rapidly as they move up the pipe, so reducing the system head throughout the system but especially at the junction with the flow pipe. This means more of the air will follow the initial bubble and none will move on to the vent pipe. The water head in the vent will be lowered and could even allow more air in that way. Water will certainly be expelled from the circuit and it's recharging will be obstructed by the counter flow of air - this is a 15mm pipe. Add to that the potential for further air input through bleed valves - depending on position - and one can see an escalating problem. That is what I think we are seeing and I hope to fix it soon.
I notice two irregularities on the installation - Vaillant vented ecotech plus (inst. guide). One, the pump is in the return pipe before the boiler and drives through a raised loop with no bleed, Two, the feed and vent are within 150mm in the flow circuit but the wrong way round.
Number one exacerbates the problem but I am sure when we swap them round two will be the real cause.
When air/water mix flows down the flow circuit, the first opportunity the air gets to escape is the water feed pipe (15mm). It takes it, the bubbles expand rapidly as they move up the pipe, so reducing the system head throughout the system but especially at the junction with the flow pipe. This means more of the air will follow the initial bubble and none will move on to the vent pipe. The water head in the vent will be lowered and could even allow more air in that way. Water will certainly be expelled from the circuit and it's recharging will be obstructed by the counter flow of air - this is a 15mm pipe. Add to that the potential for further air input through bleed valves - depending on position - and one can see an escalating problem. That is what I think we are seeing and I hope to fix it soon.
