'Super' furnace could mean a hot savings of $400 a year


January 14, 1995|By James Dulley | James Dulley,Special to The Sun

Q: Does it make economic sense to replace my noisy old gas furnace (it still works) with a new "super" model? Will a super furnace reduce chilly drafts and clean the air better for my allergies?

A: The answer to all your questions is "Yes." Older gas furnaces operate at about 60 percent efficiency. Installing a new super furnace at 95 percent efficiency can cut the typical family's utility bills by up to $400 per year.

Several new models use "smart" ECM blower motors. If a carpet slides over a register, the motor senses (checks every five

seconds) greater resistance and speeds up to compensate. Also, efficient ECM motors use two-thirds less electricity than standard motors, for an additional $100 savings per year.

Central air conditioners operate more efficiently with a new super furnace blower and comfort is improved. Some new furnaces are designed smaller to provide extra space for larger, high efficiency air conditioner coils.

Most of the design changes for the 1995 furnace models target improvements in comfort and indoor air quality -- two-stage (low/high) output burners, variable-speed blowers, more sophisticated temperature controls, quieter operation and cleaner indoor air.

The highest-efficiency super furnaces use a two-stage burner. On low fire, the burner uses about 40 percent less gas than on high fire. The blower also runs slower and much quieter on low fire. These typically cost about $400 more than a single-stage burner model.

Other than on the coldest days, the furnace runs on low fire. At this lower heat output, it stays on longer. This maintains steady room temperatures (only 1 degree swing) and eliminates chilly drafts from a high blower speed.

For someone with allergies, this is a plus. By keeping the furnace running longer, the central air cleaner has more time to remove allergens from the air.

Super furnaces use condensing heat exchangers. Sealed combustion designs use outdoor combustion air to minimize drafts and the possibility of carbon monoxide poisoning. By capturing nearly all the heat, the cool flue gases are blown outdoors (induced vent fan) through a small plastic pipe.

Because no chimney is needed, these furnaces are ideal for converting from costly electric heat to gas. Even if natural gas is not available, heating with bottled gas may be less expensive than using electric heat. Bottled gas conversion kits are available for all super furnaces.

Write for Utility Bills Update No. 992 showing a buyer's guide of 21 super-efficient gas furnace manufacturers listing efficiencies, heat outputs, blower speeds, dimensions, burner types, sealed combustion and a payback savings chart. Please include $2 and a self-addressed envelope and mail to James Dulley, The Sun, 6906 Royalgreen Drive, Cincinnati, Ohio 45244.

Q: My daughter takes long showers and often forgets to switch off the bathroom vent fan when she is finished. How long should she let the fan run and does it draw out much air?

A: It is important to run the vent fan to remove excess moisture, but running it too long wastes electricity and heated air. A typical vent fan will exhaust all the air in a bathroom in about five minutes. Running it for about five minutes after you are done showering is usually adequate.

If your daughter continues to leave it on, install a timer switch (costs about $20 at most home centers). Adjust it to shut the fan off after 10 minutes -- five while showering and five for venting.

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