QWe have periodic power failures in our area that are a real nuisance. Is it practical to install a generator to supply emergency power to our home? -- Edward

AA generator powerful enough to keep a lot of electrical appliances running can be quite expensive. If you are willing to settle for running a few key appliances, such as a refrigerator-freezer, sump pump, a TV and some lights, the cost would be a lot more reasonable. Basically, there are two types of home generators -- portable machines powered by gasoline ($500 and up, depending on output) and standby generators powered by natural gas or propane ($5,000 and up).

Portable generators have to be started and plugged in, and operating and maintaining them can be a hassle, especially because many power failures occur at night and are accompanied by heavy rain or high winds. A few extension cords can be run from the generator to specific appliances, but it is better to have special wiring installed. Portable generators shouldn't be set up in enclosed spaces, since they produce deadly carbon-monoxide gas.

A standby generator will switch on automatically during a power failure, even if you are not at home, and shut itself off when power is restored. Wiring for a generator is definitely a job for an experienced pro.

Contractors who install both types of generators are listed in telephone directory pages under Generators -- Electric and Gas.

You can get a rough idea of how big a generator you need by adding up the watts used by the equipment you want to run. Actual wattage ratings can be found on appliances, but it might take a lot of searching. Charts are available to give approximate wattages for various types of appliances, although these can be ambiguous because wattages vary with the type and size of the appliance (for example, one chart lists 600 to 2,000 watts for a refrigerator-freezer). For one such chart, see http://www.atozrentals andsales.com/atozgenwatt1.htm. After adding up the watts, add about 50 percent more to cover the higher start-up draw of most appliances. For more accurate sizing of a generator, it is best to depend on experienced dealers or installers.

Nail heads are popping up through our sheet vinyl flooring. What can we do about this? -- A. Gabler

The nails were probably used to fasten some sort of underlayment, possibly sheets of thin plywood. With a sheet vinyl floor, the best bet is to pound the nails back into place using a nail set or small punch. These pointed tools should do the least damage to the sheet vinyl.

There's a crack in my concrete basement floor that's about two feet long and 1/4 -inch wide. I bought a tube of concrete crack filler but am not sure how to prepare the crack. Can you help? -- J. Costantino

If the crack isn't leaking water into the basement, a patch of that concrete filler should be okay. The crack should be completely dry and should be cleaned of loose dirt and dust with a small paintbrush. If the crack is deep, push some foam-plastic backer rod (sold at home centers) into the crack to bring it to about 3/8 -inch deep. Finally, squeeze in some crack filler and smooth it with a putty knife.

If the crack lets water seep into the basement, it is best to repair it with hydraulic cement, sold in powder form in small containers. Fast Plug is one brand. Clean the crack as described above, then mix some cement with water and force it into the crack with a putty knife.

Questions and comments should be sent to Gene Austin, 1730 Blue Bell Pike, Blue Bell, Pa. 19422. Send e-mail to doit861@aol.com. Questions cannot be answered personally.