Water pressure below 1 bar on Greenstar 30Si Combi Mk III. How

1Understand how they work. Combination boilers work on what’s known as sealed central heating systems. Meaning they are completely free of Tanks, and natural air supply. This is essential not least because if a mains water holding component within that boiler became defective and thus enters the Heating side of the boiler there would be potential for all sorts of problems with floods in the loft area and much more. There are many advantages of sealed central heating systems. So we need to manually regulate the amount of water actually circulating your radiators. And this is achieved through a filling loop, usually located close to the combination boiler.2Identify the filling loop, the pressure gauge and the boiler.3Practice switching the boiler controls to off before attempting to top up the pressure.4Make sure the pressure gauge can be monitored whilst accessing the filling loop. The biggest mistake that can be made is over pressurizing the boiler; this is usually caused by not monitoring the gauge as you increase the pressure. If this is not achievable then ask for a friend or family member to assist by looking at the gauge as you take care of the filling loop.The ideal pressure for any sealed system is 1.5bar (displayed on the pressure gauge).The filling loop will have a silver flexible tube with two handles on each side of it. When the handles are in the off position they will be across the flow of the pipe. You will need to slowly turn them so that they straighten up in line with the pipe.By now you should hear the water flowing through into the boiler.5Keep an eye on the pressure gauge as it slowly creeps up to the green area or the 1.5 bar marker. Anywhere between 1 bar and 2.2 bar is fine.6Turn the handles back into the original position.A

Hi my name is Brian,
I have been in the Plumbing & Heating trade for approximately 15 years,
lets see if i can help. Push the white key in fully twist it half a turn so it wont come back out then turn your black tap on, I think there is only one just have another look under there if it doesnt fill when you turn it on. Get to a pressure of 1 to 1.5 with the boiler cold. turn tap off and remove key. Hopefully job done..

Hi I am Rick, UK Plumber, and I specialize on Boiler problems, OK there are two possible problems here, 1, the key system was not fully fitted and there is a separate filling loop at another place usually near the boiler but can be any place that the cold main runs near the heating pipes. 2 the key is not going in correctly, often this is due to the O rings being dry, so apply a smear of petroleum jelly or similar to the key and insert it as far as it will go before twisting clockwise fully then open the square plastic valve it may be white or black, you should hear water flowing, if not then there is a blockage that will need to be manually cleared, after draining down, Rick