Fixit: Keep cat litter away from furnace

Q Is it true that cat litter boxes need to be kept away from the furnace? Last summer, a heating and air conditioning technician said that the efficiency of our central air conditioning unit had been diminished by approximately 30 percent because the cats' litter box was within a few feet of the furnace. He said this was caused by dust generated by the litter, which then collected on the damp coils. Is this true? If so, can it be resolved by using a nonclay litter such as newsprint litter?

A Yes, it's possible, according to George Youngvorst, a senior instructor in Heating, Ventilation and Air Conditioning (HVAC) at Dunwoody College of Technology in Minneapolis.

Keep the litter box away from the furnace, but that's not all. Keep away paints, solvents and similar types of corrosive materials that might off-gas into the area where the furnace is.

Youngvorst explained that the acidic property of the litter, along with the "dust" that may be generated, could put a layer of film on the indoor air conditioning coil. This layer acts as an insulator and can keep the coil from transferring heat as it's designed to do. How much efficiency is lost would depend upon the thickness of the layer on the coil. But the coils can be cleaned. Youngvorst recommends you have a HVAC technician do the job.

Changing litter type may not make a difference; keeping the litter box away from the furnace will.

More than potholes Q When streets are repaved with asphalt, why do so many manhole covers end up recessed below the new street level? It really makes for a bumpy ride, especially in winter while we're also dodging potholes.

A By design, the manhole covers are set a quarter of an inch below the surface so snowplows don't catch them. But it isn't always just a quarter of an inch. Workers will err on the side of caution, so the covers may end up a little deeper than that.

The deepest set manhole covers tend to occur when a street is resurfaced. In that case, the street surface is ground down and a new cover laid. The manhole covers aren't pulled and reset, however, so that results in a wide variability in height.

Source: Department of Public Works, Minneapolis Send your questions to Fixit in care of the Star Tribune, 425 Portland Av. S., Minneapolis, MN 55488, or call 612-673-7032, or e-mail fixit@startribune.com. Past columns are available at www. startribune.com/fixit. Sorry, Fixit cannot supply individual replies. Fixit appears every day in Variety except Friday and Sunday.