Gas and Oil Home Heating Furnaces - Steam radiators?

Hi,
I own a older home in NewEngland.It has a oil fired steam boiler, appox 20yrs old.with the large radiators.It heats good.
In two of the smaller bedrooms,it gets too hot at night.There is a shut-off valve on the side,near the floor.Can this be used to limit the amount of heat output of that radiator?If i shut it off half way,will it still heat,but less.This won't harm the system will it?Thanks.Charlie:confused:

Danfoss Inc.; Ammark Corp.; and Honeywell make a non-electric thermostatically controlled valve for Steam 1-pipe and 2-pipe systems. This works very well when it's used to control over heating and does not when more heat is required. Closing the valve partially will not work. What all air vent valves do is allow the air to vacate the radiator so the steam can enter it. In other words, steam cannot occupy a space that's already occupied by air. The faster the air leaves, the faster you get heat, the slower, the slower you get heat from that radiator. If you control the opening and closing of the air vent valve, which these type of valves do, you control the amount of heat or temperature in the room.

Thanks for the reply,
As a matter of fact mine have adjustable air valves on the sides.
This radiator was full open.I adjusted it to 1/2.We'll try that.
Thanks again,Charlie

<img src="http://www.resercon.com/valves.jpg" >
We are not talking about the same types of valves. The type of valve you presently have does not take into consideration heat loss and gain when controlling room temperature, but this one does.

Hi,
I see they are different than what I have on my unit,but wont turning the air valve from open to 1/4 help cut down the amount of heat given off by that radiator?thanks, Charlie:confused:

The type of valve you presently have will delay or slow down the amount of heat going to that radiator. They are used to try and balance the system by doing that. Another way of saying it is slowing down the steam from entering this radiator may result in the boiler going off before it has a chance to over heat the room. However, if the slow down is insufficient and there is still a demand for heat in the other rooms, especially where the thermostat is, that room will still over heat. On the other hand it may just work by closing your valve. The only real problem I see is temperature swings. Such as, if the temperature is mild, the room may over heat. If it's very cold, the room may not heat well. On the other hand, you can just keep on adjusting the valve as the temperature changes outside.