Expansion tank pressure

[Rekusu]

What ho one and all,

Owing to a minor hot water issue, I turned off the mains and depressurised the system before checking the expansion tank pressure. The system is mains feed with a PRV set to around 3 bar. The expansion tank reading was 0.75 bar.

Assuming that the tank should be around 3 bar (?), do I just hook up the car tire inflator a wait until I have around 3 bar on the dial? Or do I have to drain some of the water from the expansion tank?

Thanks

 

[Dereekoo]

If you are saying there is no water pressure in the system and the expansion tank is at 0.8 bar then this is the correct pressure for a non pressurised system (check boiler manufacturers spec to confirm this). Just a question of pressurising your system with water to about 1 bar (again check boiler manufactures spec)

 

[Rekusu]

We have mains water pressure throughout the house but two of the hot water taps are blasting air and water. Don't know where the air is coming from and it does clear, but like the Terminator, it does return.

The house water pressure is about (or less than) 3 bar. Checked the expansion tank to find that it is around 0.75 bar. From what I can discover, it should be nearer the mains pressure of 3 bar.

The UFH expansion tank is around 1.25 bar, which is more or less correct. The pressure dial on the boiler also shows 1.25 bar.

 

[Rodders53]

Is this an unvented hot water cylinder pressure vessel? White usually.

Or a boiler pressure vessel? Red usually.

The manufacturers installation manuals should specify the setting and how to do it...