The first thing you need to do is make sure you have enough pressure in the boiler, and that your fill valve is working and the water to the boiler is on.
The pressure should be between 12 and 20 pounds. The needle on the bottom shows the pressure in PSI black print
The green handle in the back is the water valve yours may have a round handle clockwise is off counter clockwise is open. The item with the black piece on the top is the fill valve. (yours may look different) this puts water into your system if it is needed. This can be complicated if you are not sure you can do this yourself, Maybe you should call a Professional.
For the time being lets assume that the fill valve is working normal and the water is on. You will need a hose. take a good look at the next picture Click on it for a larger image) the vertical pipes coming out from the top of the boiler are the supply and return lines of your heating system.
The one on the left is the supply (on this boiler yours may be different) the two green things are your zone valves. The one on the right is your return. notice that on the right there are two red handle valves and two blue handle valves. The red handle valves are gate valves and stop the flow of water if turned off (yours may not be red or may be the lever type seen in the first picture) The Blue handle valves are boiler drains. you will need to hook your hose up to the one of the blue ones one at a time. with the hose hooked up to one of the boiler drains, turn the red gate valve off (clockwise) then make sure your zone valve is in the manual open position. then open the boiler drain. till the water is flowing slowly don't let the pressure go below 12 psi while you do this and let the water flow till you don't hear any more air coming out (about 10 minutes) repeat this with all zones that need to be purged. Don't forget to open the gate valves when you are done and put the zone valves back to auto.
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