Q - I have made energy improvements to my house and my furnace doesn't come on as often or for as long as before. How can I tell if my furnace is oversized for my house now - and is that inefficient? R.T.

A - When you make your house more energy efficient by insulating, caulking, etc., its heating needs are reduced. This is why your furnace runs less often and for a shorter time.Your furnace may no longer be an energy-efficient match with your house and may be losing too many of your energy dollars up the chimney. In fact, if your furnace is more than 10 years old, it probably was too big initially. Contractors often determined the proper heating capacity and then sized the furnace several percent larger for good measure.

A furnace loses a substantial amount of energy when the burners are off, called off-time losses. Since the flue and chimney are still hot, an upward draft continues after the burners go off. This draws already-heated air out of your house and may create chilly drafts.

These can make you feel colder, so you often turn up the thermostat, wasting even more energy. A properly sized furnace that runs more frequently also provides more comfortable and even heat and better air-cleaning.

The most accurate method to determine if your furnace is too large for your house is to have a furnace contractor do a computerized heat loss analysis on your house. Contractor sometimes charge for this analysis unless you purchase a new furnace.

He may use a simple "on-off-cycle" chart first. He will have you rec-ord how many minutes your furnace runs for an hour and the outside temperature. You should make several readings at several outside temperatures. If this indicates an oversized furnace, he will do the computerized analysis.

If you find that your furnace is too large now, you may be able to have it downsized. Your furnace technician may be able to change the nozzle or orifice sizes or block off portions of burners.

Even though your present furnace is working properly, you are sometimes better off by replacing your furnace now with a new and smaller capacity high-efficiency model. It can save money in the long-run and greatly increase your family's comfort.

You can write to me for UTILITY BILLS UPDATE No. 066 showing a simple "on-off-cycle" chart to check if your own furnace is properly sized, and a chart showing the savings from replacing your furnace with a new highefficiency one. Write to James Dulley, The Deseret News, 6906 Royal Green Dr., Cincinnati, OH 45244. Please include $1.00 and a self-addressed envelope.

Q - I have to do some caulking around a damaged window frame outdoors. The caulk cartridge instructions say not to use it below 40 degrees. Is there any trick to using it at colder temperatures? H.A.

A - If you must caulk in cold weather, your best chance for a good job is to try to raise the temperature of the area around the gaps and of the caulk itself. You will need a helper for this.

First, store the cartridge indoors to make sure it's warm. Run an electric extension cord outdoors to the damaged area. Wrap the caulking gun, with the cartridge in it, with a regular heating pad to keep it warm.

Have your helper direct the air flow from a hair dryer on the crack to warm it. He should direct it a couple of inches ahead of the tip of the caulking gun as you move it.