When to "Top Up" presurised heating system

[GolfingHero]

Hi Folks,
This is my first question on the forum but I have read many previous threads and found them very helpful, so here goes.
I have a pressurised heating system which was installed 7 years ago when my house was built.
The system incorporates a Megaflow indirect hot water tank and 2 spherical expansion chambers on the heating side.
My question, how do I check/know when or if the system requires filling?
There is a pressure guage located at one of the expansion chambers which is indicating zero.

 

[stevetheplumber]

Hi Folks,
This is my first question on the forum but I have read many previous threads and found them very helpful, so here goes.
I have a pressurised heating system which was installed 7 years ago when my house was built.
The system incorporates a Megaflow indirect hot water tank and 2 spherical expansion chambers on the heating side.
My question, how do I check/know when or if the system requires filling?
There is a pressure guage located at one of the expansion chambers which is indicating zero.

fill to 1 bar

 

[GolfingHero]

Thanks but how? do I have to open any vents?

 

[Billy Bob Bob]

there should be a braided flexible filling loop some where,try to find that first

 

[GolfingHero]

I have located that loop, it is equipped with a small ball valve, it is adjacent to the Expansion vessels located on the first floor. I have also discovered a second pressure guage which is located on the ground floor close to (below) the bolier.
I have already presuurised the system to 1 bar indicated on the first floor guage but find that the guage close to the boiler shows 1.3bar. Is this the effect of HEAD or is it more likely innaccurate guages?