how do I know if pressure bar is the black one or red one

[bambi64]

Hi can someone please help me as i am a newbie when it comes to gas boiler. There is a red hand on this one like a hand on a clock, then there is black bars also.

When I turned boiler on the red hand moved too near 3 on the boiler.
What is wrong
From Helen

 

[BingoBongo]

One is for you toove so you know where you set the pressure when cold.so you can check if it's dropping or rising too much.pressure should be 1.5 when cold and when on it will rise to 2 or 2.5 as long as it's not going over 3 and losing pressure there's nothing to worry about.

 

[djsarge1973]

Simple
RED = NOT GOOD!!!
BLACK = Good
as a rule of thumb it should be on 1 when the boiler is cold, rising to 1.5 -2 when running IF the needle goes over 3 you will hear a "bang-bang-bang" as the Pressure Relief Valve (P.R.V) dumps out the water out, if this occurs it could be the "expansion vessel" may have lost its charge or the internal Diaphram has ruptured, hope this helps