CLEANING UP WOOD HEAT FOR 1982-83

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The Stovetemp thermostat can be fitted to many (but not all) woodstoves, and it mounts with one stud and a wing nut. Our staff member/tester feels that the Stovetemp, at $39.95, is a worthwhile investment (and would be even if it offered no more than convenience). You can purchase one from any stove dealer who carries Condar products . . . or you can order a unit directly from the manufacturer (Dept. TMEN, Box 6, Hiram, Ohio 44234) for the price mentioned above plus $1.50 shipping and handling.

PART III: A SLACK TEMPERATURE WOODSTOVE THERMOSTAT

After reading our report on the Condar Stovetemp, you likely understand why we became interested in exploring the potential of automatic draft regulation for woodburners. In fact, that particular product — along with some very educational conversations with its designer, Dr. Stockton Barnett — inspired us to start tinkering on our own.

Through the late spring and early summer of this year, some of our staffers — headed by independent researcher B.V. Alvarez — have been working on a new type of thermostat. We feel that B.V. has made a real breakthrough, and he'd like to share the design (shown on page 43) with MOTHER'S readers. The device that we're about to describe sits atop a mighty pile of test models that didn't quite make it, too . . .and, perhaps partly as a result of its trial and error evolution, it's a bit different in concept from any other woodstove control that we've seen. At this point, the thermostat has been through 30 days of testing in our lab, and we're pretty satisfied with its performance. Still, it being mid-July as this is written, we naturally haven't been able to run the control through a heating season in a home. However, our testing thus far leads us to believe that we may be onto something . . .but let us tell you the whys and hows concerning the construction of our thermostat, and then you can decide.

CONCEPT

Judging from the testing done by the Condar people on their draft control, we were able to assume that the success of a woodstove thermostat hinges on its ability to react very quickly to temperature changes. With that notion in mind, we decided that it might be advantageous to use the temperature within the heater, rather than that of the metal on the stove body, to control our thermostat . . .since steel or iron takes some time to react to changes in the condition of the blaze inside the firebox.

We then decided to place our temperature sensor inside the chimney . . . in order to avoid the inaccurate readings that could be caused by localized burn conditions inside the firebox. (We reasoned that the stack gas temperature should reflect the average state of the fire below.) After trying a number of different techniques for sensing heat and driving a valve, we determined to use air as the working medium. A tube placed inside the chimney is heated by the smoke, and air inside that cylinder expands in proportion to the degree of warmth surrounding it. The sensor is connected to a diaphragm-driven valve positioned on the stove's door (though the valve could be located almost anywhere on the heater's body) by a length of 1/8" nylon tubing.

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