combi boiler presure bar is 0.

[happyman]

I have a biasi combi boiler presure bar is 0.
underneath the boiler there is a black knob, I turn it to fill the boiler but after about a few minute I turned it off because the presure guage was unchanged.
Should I have waited a bit longer or do I need filling loop?
N.B

i ALSO NOTICED THAT ON THE PIPE WORKS THERE WAS A YELLOW KNOB WHICH I COULD TURN AND A BLUE KNOB I COULD NOT TURN. WHAT ARE THESE FOR?
THANKING YOU

[gucciman]

the yellow knob is the gas and the blue knob the incoming cold mains water feed into the boiler, don't touch either of them.

what do you mean you need a filling loop? is there not one fitted already? I know your meant to remove the filling loop when its not being used but no-body ever does so you should have one. are you sure that your loop doesn't have 2 taps, 1 at each end of the loop? sometimes there can be a tap at one end and a valve that you have to turn with a screwdriver at the other end or its very common for the tap to break off.

you could try taking one end of the filling loop off and opening the tap for a very short time to see if any water is coming out.

your filling loop should or is normally a silver coloured braided flexible pipe and is connected between the thin 15mm copper pipe that carries the cold mains and the fatter 22mm copper pipe that returns the central heating water back to the boiler.

a combi boiler will normally fill very quickly when you open the filling loop, it certainly shouldn't take a few minutes, i would suggest that either your pressure relief valve is opened and the water your adding is going straight through the boiler and outside or your not actually adding any water to the boiler, another possibility is your pressure guage is broken.

if you still cant work it out then call out a heating engineer and have the boiler serviced.