As mentioned in my other post, I recently added a DHW primary circuit pump and a motorised valve to upgrade an old Profile with 28mm Gravity HW.
Here it is now:
View media item 11525
As you see, the DHW return joins the return from CH below the CH pump.
Perhaps not surprisingly, there is a modest amount of reverse flow going up the CH return, when the HW circulator is running. I am thinking a 28mm check valve (is there such a thing?) would cure that
With both pumps on Low, there is no pumping over except if HW is on, and CH is started. There is then a slight and momentary "gulp" of perhaps half a cup of water out of the vent. I am of the opinion that this is due to the back-flow being abruptly reversed. It might be relevant that all upstairs rads, and most downstairs rads, were turned off at this time. I was considering increasing the height of the vent pipe bend by 700mm or so in the hope that this will cure it. I was also considering bridging the F&E and the vent where they pass through the airing cupboard or loft. They both run horizontally in the loft for 4 metres or so before going to the F&E tank.
Both pumps are 15/50 and are currently set to low speed. When they were both on High speed during testing, there was a consistent flow out of the Vent. I suppose the HW pump could afford to be even weaker since it only has to waft the water up a 28mm pipe and round the cylinder. However there is a horizontal run of 5 metres or so under the landing floor after they have risen from the boiler before they reach the airing cupboard and rise up to the boiler.
The system is pretty clean, I used X400 twice and have a Magnaclean on CH return.
What suggestions, please?
I am not very fond of plumbing and don't want to cut and alter the pipes much more if I can help it.
Here it is now:
View media item 11525
As you see, the DHW return joins the return from CH below the CH pump.
Perhaps not surprisingly, there is a modest amount of reverse flow going up the CH return, when the HW circulator is running. I am thinking a 28mm check valve (is there such a thing?) would cure that
With both pumps on Low, there is no pumping over except if HW is on, and CH is started. There is then a slight and momentary "gulp" of perhaps half a cup of water out of the vent. I am of the opinion that this is due to the back-flow being abruptly reversed. It might be relevant that all upstairs rads, and most downstairs rads, were turned off at this time. I was considering increasing the height of the vent pipe bend by 700mm or so in the hope that this will cure it. I was also considering bridging the F&E and the vent where they pass through the airing cupboard or loft. They both run horizontally in the loft for 4 metres or so before going to the F&E tank.
Both pumps are 15/50 and are currently set to low speed. When they were both on High speed during testing, there was a consistent flow out of the Vent. I suppose the HW pump could afford to be even weaker since it only has to waft the water up a 28mm pipe and round the cylinder. However there is a horizontal run of 5 metres or so under the landing floor after they have risen from the boiler before they reach the airing cupboard and rise up to the boiler.
The system is pretty clean, I used X400 twice and have a Magnaclean on CH return.
What suggestions, please?
I am not very fond of plumbing and don't want to cut and alter the pipes much more if I can help it.
