Why is the pump coming on only when the water is up to temperature? I may be missing something but I'd have thought the most economical solution would be to have the pump running all the while the tank is heated, so the water heating backs off only when you have a full tank of hot water.
Circulaing pump is pulling air via the vernt pipe
- Thread starter GeoffJ
- Start date
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Hi mfarrow
My logic is
a) I can demand hot water at any point - when I demand hot water then it needs to be hot
b) On a cloudy or winter day I may not have the energy to heat the whole tank
c) An average temperature tank is far less useful than having the top 3rd hot and the bottom cold
Regards
Geoff
My logic is
a) I can demand hot water at any point - when I demand hot water then it needs to be hot
b) On a cloudy or winter day I may not have the energy to heat the whole tank
c) An average temperature tank is far less useful than having the top 3rd hot and the bottom cold
Regards
Geoff
Right - sorry for the delay
The result of the Jam Jar test
When starting the pump the water level hardly moves. So there is no air coming in from the vent pipe.
So the comment by jeff the gasman seems to be correct
>The Venturi effect on some parts of a system can also have this effect.
Any views?
Is there such a thing a lower powered pump? 35W seems to be far too powerful for what I am up to.
Geoffj
The result of the Jam Jar test
When starting the pump the water level hardly moves. So there is no air coming in from the vent pipe.
So the comment by jeff the gasman seems to be correct
>The Venturi effect on some parts of a system can also have this effect.
Any views?
Is there such a thing a lower powered pump? 35W seems to be far too powerful for what I am up to.
Geoffj
You need to fit a 22mm No Stop Essex flange with 3” dip pipe and bird beak cut end or a warix flange to limit air being drawn into the circulator.
If its not a thermal store then the circulator should be bronze.
A shunt pump on a vented cylinder won't suck air down the vent.
If its not a thermal store then the circulator should be bronze.
A shunt pump on a vented cylinder won't suck air down the vent.
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You're running the risk of bacterial growth in the tank unless you have another source of heat for the winter.
you may need a negative head shower pump?
how high is the water level in the tanks from the shower head and where is the pump located?
sometimes is easier to raise tank
how high is the water level in the tanks from the shower head and where is the pump located?
sometimes is easier to raise tank
OK - I get it. I must not remove the vent pipe 
So we are certain that it is dissolved air in the water that is forming the bubbles in the pump. I guess the combination of high temperature and the reduced pressure at the pump inlet would cause this.
Any ideas on next steps- I would like to get a shunt-pump to work without gassing up.
- Is a negative head shower pump really going to change anything?
- The comment to install a "22mm No Stop Essex flange with 3” dip pipe and bird beak cut end or a warix flange" seems to only apply if air was getting in via the vent - it is not
- Yes the HW tank is also connected to the gas boiler (standard domestic install for HW + CH). it is a condensing boiler with a sealed system - The central heating side works perfectly with valves, pumps and timers.
Regards
Geoff
So we are certain that it is dissolved air in the water that is forming the bubbles in the pump. I guess the combination of high temperature and the reduced pressure at the pump inlet would cause this.
Any ideas on next steps- I would like to get a shunt-pump to work without gassing up.
- Is a negative head shower pump really going to change anything?
- The comment to install a "22mm No Stop Essex flange with 3” dip pipe and bird beak cut end or a warix flange" seems to only apply if air was getting in via the vent - it is not
- Yes the HW tank is also connected to the gas boiler (standard domestic install for HW + CH). it is a condensing boiler with a sealed system - The central heating side works perfectly with valves, pumps and timers.
Regards
Geoff
Completed a longer test with the pump now fully horizontal. Also put the jam jar on the vent pipe when air is flowing to see if any exits from the vent pipe
Still get air forming in the pump - even when the water is only luke warm - We can clearly hear the bubbles rising in the tank. Nothing is coming out of the vent pipe.
I believe that air is being created within or near the pump. It gets pushed into the bottom of the tank and then tries to go up the vent. The bubbles then get re-circulated by the pump and so there is a gradual build up in the level of air in the circuit until the pump is no longer primed and it ceases to pump.
Very keen to know the best next steps from anyone?
My logic suggests that an Essex flange is the only way to solve this. That way, most of the bubbles will be able to go up the vent, and they won't re-circulate causing the build-up.
Geoffj
Still get air forming in the pump - even when the water is only luke warm - We can clearly hear the bubbles rising in the tank. Nothing is coming out of the vent pipe.
I believe that air is being created within or near the pump. It gets pushed into the bottom of the tank and then tries to go up the vent. The bubbles then get re-circulated by the pump and so there is a gradual build up in the level of air in the circuit until the pump is no longer primed and it ceases to pump.
Very keen to know the best next steps from anyone?
My logic suggests that an Essex flange is the only way to solve this. That way, most of the bubbles will be able to go up the vent, and they won't re-circulate causing the build-up.
Geoffj
Essex flange will definitely sort it. The whole idea of any kind of flange when it's being used for a shower pump is to stop the small bubbles which naturally occur at the top of the cylinder from being sucked up. So in this case you're having the same issue.
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