It’s not common to install a house with a boiler and radiator heating system these days, but there are plenty of old systems out there. If you have this kind of system in your home, here is a guide to help you understand how it works and what you need to do for maintenance.
How the System Works
Although radiators might seem old fashioned, they provide a very comfortable and consistent heat for your building. They also don't dry out the air as much or blow dust around like a forced air system. They also tend to last a very long time, especially with proper maintenance.
In this kind of heating system, the radiator, boiler, and all the connecting pipes are filled with water. It is called a “closed system” because the water cycles through endlessly instead of draining from the house like plumbing. The boiler heats this water to about 180 degrees Fahrenheit, and a pump pushes the heated water to the radiator where the heat spreads to the air around it. Then the cooled water returns to the boiler to be heated again.
Types of Radiators
Radiators can be made from several different types of metals. Older systems tend to have cast iron radiators. If you’ve ever used cast iron cookware, you will be familiar with how this metal works. It tends to heat up slowly but then retain the heat for a very long time, even after being removed from the heating source. A cast iron radiator is no different, and will keep its warmth long after the system is shut off, making it very efficient at heating a home.
Unfortunately cast iron is very heavy and expensive, so newer radiators tend to be made of other metals like steel. These radiators work the same way as cast iron ones, but they heat up and cool down faster and tend to be lighter-weight and cheaper.
Maintaining Your Radiator
If you have a radiator, you should perform some basic maintenance once a year to keep it in the best shape possible. The most important task is to “bleed” the radiator of any air that gets into the system. Even though the pipes are closed, air can escape from the water over time. Since air is lighter than water, it rises to the top of the system, which happens to be the top of the radiator.
Bleeding this air is very simple to do:
For safety, turn off the system and allow the water to cool down (or perform this maintenance right before you turn on the system when the weather gets cooler).
Find the small valve near the top of your radiator. Since the closed system is under pressure, opening the valve will release the air. In order to open the valve, you should have a special bleed key that came with the house. If you don’t have one, you can buy a new one at a hardware or antique store, or sometimes a flathead screwdriver will work.
Hold a bowl right under the opening below the bleed valve and turn the bleed key counter-clockwise. You should hear a hiss as air escapes.
Once water starts coming out into the bowl, close the valve again by turning the bleed key clockwise.
Don’t worry if the water in your bowl looks gross, that’s normal!
Checking the Boiler Pressure
After you bleed the system of air, it’s important to check and make sure that the boiler pressure is right. Do this step before you turn the boiler on, since the temperature of the system will affect its pressure.
Open the service panel on the boiler, and you should see a gauge for temperature and a gauge for pressure. The boiler should be at 12 psi when the water is cold and 18 psi when the water is hot. If the pressure is below 12 psi while cold, you need to add some water to the system.
There will be a cold water pipe entering your boiler. To increase the pressure, slowly turn the valve controlling that pipe. Watch the pressure gauge, and when it hits 12 psi, close the valve.
If you do accidentally leave the valve open and the system becomes over-pressurized (usually around 25 psi), there is a pressure relief valve that will open so that the system will not break. However, this will result in gallons of water being dumped onto your floor, so do not leave the valve open unsupervised!
On the other hand, if your system has too high of a pressure (over 15 psi while cold), you need to relieve it. Connect a hose to or place a bucket under the boiler’s drain and open the valve until enough water has been removed. Again, keep an eye on the pressure gauge and do not leave the system draining unsupervised.
Maintaining the Combustion Chamber
In order to heat the water, your boiler has a combustion chamber that uses fire to provide heat. If too much grime builds up in the combustion chamber, it won’t perform as efficiently. Cleaning out this part of the system is dangerous because it deals with gas, oil, and fire, so it’s best to have an HVAC specialist come out to perform the maintenance every few years.
I hope this has given you a better idea of how a radiator/boiler system works and what you need to do to keep the system running smoothly and efficiently. If you properly maintain your water heating system, it can last for decades. If you have further questions or would like professional boiler and radiator maintenance, contact us at Complete Protection!