Combi losing and gaining pressure (expansion vessel or filling loop?)

[Agile]

Right, but just checking - before I start, should I completely let the air out of the expansion vessel, or does the air in there not matter?

I do advise letting all the air out before starting. This is because some water sometimes migrates to the air side and it is good to get that out first. It also gives an indication of the condition of the EXV.

Only then let the pressure out of the heating system and keep it depressurised as you top up the air to about 0.9 bar.

Tony

 

[Aquaheat]

I do advise letting all the air out before starting. This is because some water sometimes migrates to the air side and it is good to get that out first. It also gives an indication of the condition of the EXV.

Only then let the pressure out of the heating system and keep it depressurised as you top up the air to about 0.9 bar.

Tony

Why pressurise to 0.9bar when MIs request 0.5bar for a typical system?

Jon

 

[Agile]

Because my experience indicates that 0.9 bar air pressure is normally more effective with a system pressure of 1.5 bar.

It is also the figure more makers quote.

But perhaps they are thinking of a system pressure of 1.0 bar which reduces the chances of their boilers leaking. Maybe they fear they are likely to leak?

 

[Steelmasons]

Because my experience indicates that 0.9 bar air pressure is normally more effective with a system pressure of 1.5 bar.

A cold fill pressure of 1.5 bar would yield a vessel pre-charge pressure of 1.3bar.

It is also the figure more makers quote.

Absolute rubbish.