Portable air conditioners can supplement central air

Q. We have central air-conditioning. It seems wasteful to cool the entire house when just we two are home. Is using a portable air conditioner in various rooms more efficient overall?

A. Natural ventilation is the most efficient cooling. In many climates though, such as hot, dry areas or humid areas, it is just too uncomfortable without some type of cooling. A swamp cooler, which relies on evaporative cooling, is the most economical cooling source in hot, dry climates. In most other regions, a standard refrigeration-cycle air conditioner design is typically used.

Using a portable or window air conditioner is a good idea especially when you and your wife are going to be in the same room for an extended time. This also is effective even with central air-conditioning. Even though the SEER efficiency of a central air conditioner is generally higher than the efficiency of a portable or window model, using them can save money overall.

Run the portable or window air conditioner to cool just a frequently used room or two to the comfortable cool temperature you desire. Raise the temperature setting on the wall thermostat for the central air conditioner four or five degrees higher than normal. Doing this significantly reduces the amount of electricity consumed as compared to trying to keep the entire house comfortably cool.

Portable air conditioners are particularly convenient to use because you can roll one from room to room. With this feature, one portable air conditioner can be used to keep different rooms cool depending upon which room you are using. Most portable air conditioner are relatively heavy, so most people would not typically carry one up and down stairs easily. It is better to have one for each floor of a two-story house.

Portable heat pumps, which look identical and operate similarly to a portable air conditioner, also provide heating during cold weather. This efficient heating source can produce up to 12,000 Btuh from a 120-volt electrical outlet. Most electric space heaters produce only 5,100 Btuh. The thermostat is built into the handheld remote control so it senses the temperature precisely where you are sitting. I use one year-round in my study.

A flat adapter panel is used to connect the portable air conditioner or heat pump to a window with one or two 5-inch-diameter flexible and collapsible ducts. This is where heat pulled from the room air is exhausted outdoors. The window adapter and ducts, which must be moved along with the portable air conditioner, fit most easily in single- or double-hung or slider windows.

Two-duct models are the most efficient because already-cooled room air is not drawn outdoors. All the air that is drawn through the condenser coils comes in one duct, flows through the hot coils, and is exhausted outdoors through the other duct. Some models also exhaust the condensate from the dehumidifying cooling coils, otherwise you have to empty a small water tank when it is full.

The following companies offer portable air conditioner/heat pumps: Danby, (800) 263-2629,; LG, (800) 423-4142,; Soleus Air, (877) 665-9765,; Sunpentown, (800) 330-0388,; and Toyotomi, (203) 775-1909,

Q. I am having a problem with nail pops from the drywall on the ceiling. There seem to be more and more of them. I tried to fill them with compound, but it pops out again. What can I do to stop this?

A. Nail pops can have several causes, but the end result is the same. The drywall compound over the head of a nail pops off exposing the head. Just putting more compound over the hole does not work for long.

If you push on the drywall, you will probably feel it move. Drive some additional drywall screws around the pops to make sure the drywall is secure to the framing. Drive the nails in deeper and fill all the holes with compound.

• Write to James Dulley at 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit

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