A heating system is classified by the medium that transfers the heat from the furnace through the house. Forced-air, hot water and steam are the most common heating systems in the United States.
Hot-water systems have some advantages over forced-air heating. Generally they are quieter than forced-air. (This is not true of a steam system, which can be noisy.)
Hot-water heating provides radiant heat, which many people find more comfortable than forced-hot air. Hot-water systems take up less room because the water circulates in small-diameter pipes. In contrast, the forced-air system relies on large-diameter ducts to move the air around.
But hot-water systems do have their problems. For example, they are usually more expensive to install than forced-air; and they are not easily adapted for air-conditioning or cooling.
The heart of the hot-water system is the central boiler. The water in the boiler is heated by gas, oil or, in some older systems, coal or wood. The hot water circulates through pipes to radiators or heating panels that radiate the heat into the rooms. Early hot-water systems relied on gravity to circulate the water. As the water heated, it expanded and pushed into the radiators where it relinquished its heat. After giving up the heat, the water dropped to the boiler.
One drawback to the gravity system was that it took time for the water to expand sufficiently to circulate. In an effort to make the system more responsive, hydronic designers added a circulating pump to move the water through the system.
In addition to the boiler, pipes, radiators and circulating pump, hot-water systems also have an expansion tank that allows the water in the system to expand or condense without rupturing the pipes or fittings in the network.
The annual maintenance routine for a hot-water heating system should start with a furnace tuneup by a professional service technician. The technician should inspect and clean the combustion chamber and the fuel nozzle. He should also run a combustion test.
The furnace tuneup is a job for a professional, but there are a number of simpler maintenance tasks that every homeowner can do. Water systems often accumulate sludge in the form of mineral deposits and rust. To remove the sludge, simply drain a bucket or two of water from the boiler. First turn off the burner, then close the water inlet valve to the boiler.
Now position a bucket under the boiler drain valve. The water in the boiler will be hot. To avoid getting burned, it’s best to wait an hour or two before opening the drain valve. Drain the water until it runs clear, then close the drain valve, open the supply valve and turn on the furnace. Newer systems should be drained yearly, but older systems collect sludge more readily. With such a system it may be necessary to drain more frequently.
If you have an old hot-water system that’s never been drained, then drawing a few buckets of water may not be enough. You may need to call in a professional to flush out the system. This “professional flush” is done with chemical additives and very hot water.
After draining the boiler, check the expansion tank. Depending upon the age of your system you may have either one of two types. Newer systems have a diaphragm tank, which is sealed, so it’s not necessary to drain it. Older systems’ tanks should be flushed out yearly. You can easily recognize this type of tank because it has two valves–a shutoff valve going into the furnace and a drain valve on the bottom of the tank.
To drain the tank, first close the shutoff valve. Position a bucket under the drain, then open the valve. The water should flow out, but if it doesn’t, it may be necessary to open the vacuum-breaker plug (not all tanks have this plug) on the drain valve. You can open the plug with an adjustable wrench. After the tank has been drained, close the drain valve and vacuum-breaker plug, then open the shutoff valve. If all this seems like a lot of trouble, you might want to consult a heating technician about replacing your old expansion tank with a newer diaphragm model.
Next you should bleed the radiators. Bleeding releases the trapped air. To bleed a radiator, first position a pan under the bleed valve. Then open the valve. Depending upon the type of bleed valve, you can use either a screwdriver or a radiator key (available at hardware stores or plumbing supply stores) to open the valve. At first air will come out of the valve, then water. At that point, close the valve. You should bleed each radiator once or twice each year.
