Old 10-08-00, 06:32 PM
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Am unsure how to bleed radiators so that hot water will be forced through so that I'll get heat. Also I would like to replace turn valves so that when room isn't occupied radiator can be turned lower or off. The rooms in front of house are nice and warm, rooms in back are stone cold. Need this info quickly. Thanks!
Old 10-08-00, 07:34 PM
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If this is a hot water heating system, there are two kinds of radiators you can have; cast iron baseboard radiators and finned copper tube baseboard radiators.

Cast iron baseboard radiators are connected to each other by a pipe near the bottom of the radiator, SO EACH RADIATOR will have an air vent at the top. Finned copper tube radiators essentially consist of a horizontal 3/4 inch copper pipe, so they only have an air vent at the DOWNSTREAM END of each horizontal section before the pipe turns down and goes in the floor.

In both cases, the first thing to do is go to where the boiler is and check the pressure. If you guestimate the height difference from the boiler to the topmost radiator in the building in feet, then devide by 2, that should be the minimum pressure reading on the gauge, and a few extra psi above this won't do any harm. Check the gauge with the circulating pump off. If the pressure is below the difference in height/2, then add some water until it reads the calculated pressure.

Now, go to the topmost floor and turn the air vent screws to bleed the air out. Normally, the air vents will have a little slot screw on top that you can open a bit with a screwdriver, but sometimes they have a wood wheel or metal knob you turn. In every case, you turn the screw counterclockwise to open it when viewed from above.

Allow air to blow out of each air vent you find until the water starts coming out, then turn the screw clockwise (when viewed from above) to close it until the water stops. Turn it closed until the screw is snug, but don't twist the byjesus out of that screw.

If you find that the air blow peeters out to nothing while bleeding a radiator, but the water doesn't come out, it just means that there's not enough water in the system to fill it completely, and you have to add more water.

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