Pressure drops when 650 litre buffer tank is filled with water but no drop with air

[Trevor Rix]

Re: Pressure drops when 650 litre buffer tank is filled with water but no drop with a

a wild stab in the dark, is the buffer heating a dhw cylinder? maybe a leak on the coil?

Could you please read the whole thread.

 

[devoncreamy]

Re: Pressure drops when 650 litre buffer tank is filled with water but no drop with a

have scan read, my apologies. good luck

 

[missplumb]

Re: Pressure drops when 650 litre buffer tank is filled with water but no drop with a

what volume is the buffer?, why are you cold filling to 2.5 bar, should only be about 1 bar, possibly 1.5 for system with Kamstrup heat meter. only having 0.5 bar expansion on a system of 3000 ltrs is very likely to cause is to blow off. It doesnt take much of a leak at 80 degrees to lose that much pressure, and it will evaporate quite quickly. Also looking at pic 4, the strainer is upside down. Im not sure what the water regs are in Suffolk but in North Yorks, any system over 45kw is required to have an automatic filling system.

 

[Trevor Rix]

Re: Pressure drops when 650 litre buffer tank is filled with water but no drop with a

what volume is the buffer?, why are you cold filling to 2.5 bar, should only be about 1 bar, possibly 1.5 for system with Kamstrup heat meter. only having 0.5 bar expansion on a system of 3000 ltrs is very likely to cause is to blow off. It doesnt take much of a leak at 80 degrees to lose that much pressure, and it will evaporate quite quickly. Also looking at pic 4, the strainer is upside down. Im not sure what the water regs are in Suffolk but in North Yorks, any system over 45kw is required to have an automatic filling system.

Sorry for the slow reply. I did not receive a notification. Thanks for your observations.

The buffer is 650 litres. I am the customer/end user, not the installer/plumber. The pressure switch now installed (not shown in photos) is set to inactivate the boiler at 0.6 bars, so 1.0 bars would not provide much leeway. The installers decide on the pressures for testing purposes, not me. I think the normal operating target is 1 to 2 bars, the upper limit being the blow off point on the buffer of around 2.8 bars. The heat meters are Sontex.

Where do I find the strainer are you referring to? I did not know there was one.

Are saying that there should be an automatic topup of mains water if the pressure drops too low? I have not heard of that before.

 

[trplumb]

Re: Pressure drops when 650 litre buffer tank is filled with water but no drop with a

Sorry for the slow reply. I did not receive a notification. Thanks for your observations.

The buffer is 650 litres. I am the customer/end user, not the installer/plumber. The pressure switch now installed (not shown in photos) is set to inactivate the boiler at 0.6 bars, so 1.0 bars would not provide much leeway. The installers decide on the pressures for testing purposes, not me. I think the normal operating target is 1 to 2 bars, the upper limit being the blow off point on the buffer of around 2.8 bars. The heat meters are Sontex.

Where do I find the strainer are you referring to? I did not know there was one.

Are saying that there should be an automatic topup of mains water if the pressure drops too low? I have not heard of that before.

Automatic top ups can introduce fresh water into your sealed heating system and causes oxidising(very bad). U needa sort out the leak!!!!
1.. If xpan ves is set at 1.5bar then your sealed system should be the same pressure. Pres drops can be caused by any one of your blow offs(exp relief valves) expelling water through pipework to outside where it cant be noticed(check tundish is dry). Blow offs arent accurate(less 3bar)
2..One off isolating valves letting water through when meant to be closed.
3..Pin hole in any coil fitted to buffer.

 

[Trevor Rix]

Re: Pressure drops when 650 litre buffer tank is filled with water but no drop with a

Automatic top ups can introduce fresh water into your sealed heating system and causes oxidising(very bad). U needa sort out the leak!!!!
1.. If xpan ves is set at 1.5bar then your sealed system should be the same pressure. Pres drops can be caused by any one of your blow offs(exp relief valves) expelling water through pipework to outside where it cant be noticed(check tundish is dry). Blow offs arent accurate(less 3bar)
2..One off isolating valves letting water through when meant to be closed.
3..Pin hole in any coil fitted to buffer.

There are no automatic top ups.

What leak? The problem is that there was no leak. There were unexplained pressure drops, fast enough drops to switch off the boiler within a couple of days, that stopped dropping during testing when air replaced the water. The whole system is now filled with water and is up and running with everything connected and working.

There are only two blow offs, one on the buffer tank, and one on the boiler in case of excess heat. They are not blowing off.

There are no isolating valves that are turned off.

There are no coils.

 

[Last Plumber]

Re: Pressure drops when 650 litre buffer tank is filled with water but no drop with a

Is this still going on ?
I've not looked at this thread for weeks.

 

[Trevor Rix]

Re: Pressure drops when 650 litre buffer tank is filled with water but no drop with a

Is this still going on ?
I've not looked at this thread for weeks.

It's still going on in the sense that the cause of the drops in pressure is unresolved. It's as if replacing the water with air magically stopped the pressure drops. This is logically not possible. No one who has looked at the system and no one in this thread has come up with a plausible explanation.

The system is now working and is being monitored for pressure drops. So far so good.

 

[ShaunCorbs]

Re: Pressure drops when 650 litre buffer tank is filled with water but no drop with a

It's still going on in the sense that the cause of the drops in pressure is unresolved. It's as if replacing the water with air magically stopped the pressure drops. This is logically not possible. No one who has looked at the system and no one in this thread has come up with a plausible explanation.

The system is now working and is being monitored for pressure drops. So far so good.

have you pressure tested the system yet?

 

[Last Plumber]

Re: Pressure drops when 650 litre buffer tank is filled with water but no drop with a

Wierd !

Air will obviously contract a lot. So the temperature of air put in, once stabilised will drastically change pressure just like testing a large gas installation but you've thought of that ?