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Check out heating system before you need it


ALL IT takes is a few nippy nights, like the ones we've had lately, to remind folks it's getting to be time to turn on the heat. Some of us have personal rules about this -- one of Karol's colleagues absolutely, positively never turns on the furnace until November -- but whatever the imperatives, it's nice to know that when you need it, you can flip the switch and have the apparatus work.

Of course, it helps to know what is supposed to happen, and how things are supposed to work. Here's a primer on heating systems, so you can check yours out before you really need it.

The term encompassing all the systems that control the climate in your house is the acronym HVAC. It stands for heating, ventilation, and air conditioning. It applies to heat pumps, furnaces, coils, condensers, pipes, ducts -- all the things that heat or cool the air inside, keep air circulating, and vent the unwanted cooled or heated air to the outside, according to season.

There are numerous types of heating systems. The most common modern system is forced air, in which air is heated in a chamber and blown (or forced) throughout the house through ductwork.

The biggest advantage of forced air is that it heats evenly, and it can use virtually any kind of fuel. In addition, once the ductwork is in place, it's relatively easy to add air conditioning. However, a duct system designed for heat will still require some modification for air conditioning.

With forced air, heating works best when vents are in the floor, and air conditioning works best when vents are in the ceiling. In either system, the air has to keep circulating. In a heating system, the heavier, cooler air will fall, and return air vents near the floor collect it and carry it back to the air handler. In an air conditioning system, the lighter, warmer air collects near the ceiling, and vents high up catch it and return it to the air handler. (The air handler is what most people call the furnace. It includes a blower and may include both a device for heating and a coil for cooling.)

A retrofitted cooling system will require some changes to get high returns. When air-conditioning systems don't work very well -- if it's much hotter upstairs, for instance -- it's often because air returns are inadequate. There are three ways to alleviate this problem. If you have separate trunk lines for the upstairs and downstairs, you can install a damper in the downstairs line that can be shut off in summer so it forces more air upstairs. You can also close off vents downstairs to force more air upstairs. Installing a high return will help the most; it not only allows warm air to be recirculated, it also lowers air pressure in the house and allows more air to come out of the registers.

Disadvantages of forced-air systems include reduced humidity in the house and a perception of drafts from blown air (even though it may be hotter than the air in the room). Dry air can make people feel uncomfortable, and eventually it can damage wood and furniture.

When it's time to turn on the heat, there are some routine types of maintenance that will ensure you stay toasty all winter. The first thing is the simplest: Change the filter -- and keep changing it, at least every other month. A dirty filter reduces air flow and makes the system inefficient.

Chimneys and flues need to be maintained as well. They can become clogged -- with debris such as leaves, or a bird's nest. In an oil-fired system, there will be residue from burning that clings to the sides of the flue and can cause blockage. (If you use a fireplace at all, you need to make sure the flues are cleaned periodically. Blockages can cause fires and buildup of dangerous fumes in the house.)

In older houses, the most common type of heating is a boiler system, in which water is heated and hot water or steam is distributed through pipes and/or radiators. The boiler may be fired by gas or oil.

The biggest advantage of radiators is that they don't dry out the air, which helps people feel more comfortable and warmer, and the moister air helps preserve wood and furniture. People who have these systems prize them for their warmth -- and they make great places to dry wet mittens.

The biggest disadvantage is that you can't simply add air conditioning to the system; you have to install ductwork. There are also small things that can go wrong: Pipes and valves can rust, and air blockages can make radiators inefficient. Radiators are also hard to clean and very hard to paint. And replacement parts are not readily available.

Before you turn on the heat, get a service person to check out the burner. The devices that deliver fuel to the flame can become clogged, causing it not to work, or not to work efficiently. Both gas and oil burners have safety features that ensure fuel is being burned; they need to be checked by a professional to make sure they are in place.

Boilers also have flues, and they need to be checked to make sure they're clear. Failing to maintain a boiler system can lead to buildup of dangerous fumes in the house, even to fires. A small problem can make people living in the house ill; a big problem can kill people.

Both these systems -- forced air and boiler -- are getting to be somewhat old-fashioned. Next week we'll talk about more current systems -- such as heat pumps -- and some that are getting to be more popular -- such as solar, geothermal and radiant heat.

Pub Date: 9/13/98

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