Q - We want to stay as comfortable as possible, yet lower our heating and air-conditioning costs. Is there any way to set different temperatures in various rooms with one single central forced-air furnace? W.K.

A - A typical central forced-air heating and air-conditioning system with one thermostat is not very energy efficient. It is wasteful to keep unoccupied rooms, like bedrooms, warm all day.Some rooms, like playrooms, exercise rooms or kitchens, needn't be kept as warm as a living room for adequate comfort. Each degree you can lower a room's temperature can reduce the heat loss from it by 2 percent to 3 percent.

There are several new special types of "zoned-temperature control" systems available that allow you to set different temperatures in various rooms with one central furnace. These can be used with your present furnace and duct systems to control the amount of heated or cooled air going to the various rooms at various times throughout the day and night.

Zone-control systems use separate thermostats in several rooms (two or more zones) of your home. Each thermostat controls both the furnace burner and a special motorized damper baffle in the hot air duct going to the rooms in that zone. For example, your house could be divided into zones of the kitchen, the dining and living rooms, the bedrooms, the family room.

When a specific zone reaches the temperature setting on that zone's thermostat, the damper in that duct closes. Even though the furnace burner stays on to heat other rooms, the closed damper blocks any more hot air from going to rooms in that zone. When the temperature drops a little below the thermostat setting in that zone, the damper partially opens again.

Therefore, the hot air only goes to the rooms that need it. If you are baking in the kitchen, there may already be enough heat so the damper to that zone stays closed. That way the furnace isn't wasting heat and making you uncomfortably warm by blowing hot air where you don't need it.

The most energy-efficient system uses a clock-type thermostat in each controlled zone. This automatically lowers the temperature in the bedrooms after you wake in the morning. At the same time, the temperature in the kitchen and living room, which was set lower at night, is set higher.

These zone-control systems are particularly effective with the new superhigh-efficiency multispeed furnaces and heat pumps. With only several rooms requiring heat at any one time, the furnace or heat pump can run in the energy-saving low-output speed most of the time.

You can write to me for UTILITY BILLS UPDATE No. 203 listing the manufacturers of zone-control systems and product information and specifications. Write to James Dul-ley, The Deseret News, 6906 Royal Green Drive, Cincinnati, OH 45244. Please include $1 and a self-addressed stamped business-size envelope.

Q - I live in an apartment with electric baseboard radiators. How often should I clean them, and should I use my vacuum cleaner to remove the dust? G.X.

A - You should clean off the dust and dirt with your vacuum cleaner about once each month. If you have a dog or cat that sheds heavily, increase the frequency of the cleanings.

As the radiator gets dirty, not only is the air flow blocked, but the dust insulates the heating fins from the room air. When cleaning the radiators, make sure to get the vacuum nozzle inside to the heating fins as much as possible, from both top and bottom.