Thatchmont Condominium

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Fix Radiators for Control Over Heat

There is a shut off valve for each radiator located at the bottom where the radiator connects with the main pipe. This should be completely open if you want the radiator to provide heat or completely closed if the room is too warm after adjusting the radiator. Do not use this valve to adjust the heat. Doing so causes the pipes to bang.

To control the amount of heat each radiator provides to the room, you must have a working adjustable air valve. This is located on the side of the radiator opposite where the shut off valve is attached. When the main system is supplying heat, the air valve will hiss, letting air escape from the radiator and allowing steam to enter the radiator and give off heat. Each air valve contains a column of liquid that expands with heat, so that the air flow through the valve is interupted once the radiator gets hot.

A good air valve allows this shut off to occur from quite cold to quite hot. The longer the air valves stays open, the more heat the radiator will provide for the room. A cheap or broken air valve won't allow for much control and should be replaced.

The air valve can have several ways to adjust it, depending on what model you have. In most units there is a knob next to the air valve that has a set of numbers on it. As the knob is turned, so that the numbers at the top increase, it increases the rate that air can escape through the valve and the amount of heat that the radiator provides to the room. This should be adjusted to obtain the most comfortable temperature. Note it will take several hours after you adjust the valve for the room to reach the new temperature. It should be adjusted in small amounts each time to obtain optimum comfort. You may also find that when it is sunny or very windy, you may have to make small adjustments to the air valve to keep the room at the desired comfort level.

Air valves can be replaced by unit owners who are familiar with plumbing techniques. Replacements are available at Aborn Hardware on Harvard St. Home Depot has them but the model they carry doesn't work well. 

To replace your air valve, close the shut off valve at the floor. Remove the faulty air valve. Put one or two turns of Teflon tape over the threads of the replacement valve. Screw the new valve into the radiator until it is hand tight. Turn it an additional amount so that the valve points up (don't force it to avoid breaking it off!). Close the air valve adjusting knob and open the shut off valve. Check that the radiator does not get hot when the heat is on. This indicates that the threads are not leaking air and the air valve adjustment works properly. Then adjust the air valve to reach the desired comfort level.

For better control of the temperature in your unit, you can install thermostatically controlled air escape valves. These only allow steam to enter the radiator when the air temperature in your unit is too cold. They are described at http://www.thisoldhouse.com/toh/video/0,,1638722,00.html

 Air valves may also be replaced by a plumber.

Banging or Noisy Radiator Pipes

The radiators we have here are single-pipe steam radiators. This means that steam rises into the radiator, condenses into water, and runs back down the same pipe it came from. The banging and clanking that sometimes occurs is caused when there is an obstruction so the steam bubbles up through collected water.

This is usually caused by one of two things:

1. The radiator floor valve isn't turned open all the way. These things are only either on or off, and cannot be adjusted to be part of the way on. If the valve is partly but not completely closed, water collects and the steam bursts through it causing much noise. If you can't move the valve, you probably need to get it replaced because it is corroded.
2. The radiator isn't leveled right. It should be higher on the end away from the floor pipe. If not, water can collect in the radiator rather than running out quickly enough.