Do It Yourself: Window AC units outperform portables

Q. We are considering a portable air conditioner for our 250-square-foot living room, but know little about these devices. Would it need an electrical circuit by itself? How is it vented and is it better than a window air conditioner?

A. Portable air conditioners differ from other air conditioners in that they can be moved about on wheels. A portable unit for a 250-square-foot room would need at least 10,000 BTUs of cooling power.

Air conditioners are high wattage devices, using a lot of electricity to operate, and it is likely that a portable of this size would draw 1,200 to 1,500 watts, depending on its energy efficiency. In many homes, that much wattage would monopolize an electrical circuit and you would not be able to plug in any other equipment – except low wattage devices like lights or a radio – without overloading the circuit and tripping a circuit breaker.

You should have an electrician check your wiring and the capacity of the circuit or circuits where you plan to use the cooler. You should also make sure that the unit you buy can be used in those circuits. You’ll need grounded outlets, and some units might even require a 240-volt outlet. The electrical requirements might hamper any plans you have to move the unit from room to room.

Portables expel both heat and water, and many come with a panel that fits in the bottom of a double-hung window. The flexible exhaust pipe protrudes to the outside through a hole in the panel. Some portables expel the water into a container under the unit; this must be emptied regularly. Others (usually better performers) have two exhaust hoses, one for water; this can also lead to installation problems.

In general, window units are more efficient in cooling and use less energy and often cost less.

Q. I have small rotted areas in several wood window sills, and I want to patch them before repainting. I’ve used the two-part wood filler and don’t like it much because of the very strong odor and difficulty in smoothing. Is there something easier I can use?

A. Try Minwax Stainable Wood Filler, a ready-to-use latex product that worked well for me. It can be painted as well as stained, is relatively easy to smooth with a putty knife and sandpaper, and dries quickly.

This product comes in a 1-pound container for larger jobs, or in a 6-ounce toothpaste-type tube if you need only a little. It has a texture much like wood and comparatively little odor.

If these are deep holes, apply the filler in 1/4-inch layers and let each layer dry before adding another. When you sand, use rather coarse sandpaper at first, about 80 grit, then switch to a finer grit to finish smoothing. Be sure to read the directions and cautions on the container before using.