A Shore homeowner wrote me several weeks ago about replacing an air-conditioning unit and expressed disappointment that I didn't show up to install a new unit guaranteed to last 100 years for free.

Yet the problem of salty ocean air doing in air-conditioning units before their time is very real.

In this space, I recommended research, including contacting contractors who work at the Shore and asking neighbors about their experiences.

Hank Ohls e-mailed the day after that column appeared, offering advice. Ohls has owned a beachfront townhouse in Sea Isle City for 25 years.

When the duplex townhouses were constructed, the builder put the outside condensers on the ground-level beachfront deck, Ohls said. The units lasted four to five years before they had to be replaced.

Ohls believes they rusted because of exposure to coastal storms and salt spray.

A few years ago, when he had to replace another condenser, he had the contractor put the new one on the west side of the building on a deck, where it would be protected from coastal storms. The plumbing tubes were installed in the crawl space under the house.

The condenser was an upgraded "seashore" model, made by Carrier, Bryant and others. The Carrier Infinity Coastal model, for example, is designed for use within 10 miles of the seashore. The coils are coated to deter corrosion. Such models come with enhanced warranties.

But not every situation is exactly the same, and Ohls was careful enough to do his research and take the kinds of precautions that experience and common sense dictate.

Since doing that, there has been no rust so far, Ohls said.

Question: I primed and painted bare pine, but the knots bled through.

The knots were again reprimed and repainted, and the knots bled through again.

Next, I tried two coats of polyurethane before any painting. The knots bled through again.

What I can do to permanently seal the knots?

Answer: I have had unquestioned success with two primer coats of Zinsser B-I-N primer-sealer, which is shellac-based.

Or, you can save yourself work by buying higher-grade pine with no knots.