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slow wax motor
Monday, March 2 2009
Today I turned my attention to the low-voltage wiring and electromechanical valve controlling the new hydronic loop to Gretchen's basement library. While the six existing zones are controlled by Honeywell valves, the new zone valve was made by the Taco company and it only came with three connections. The activation circuit (to close the valve) shared a common wire with the "zone has closed" switch. The crazy wiring of my particular boiler wouldn't allow for such a shared terminal, so I had to pull the Taco valve apart, snip a wire and run an additional wire out of its controller head. It was all simple macroscopic 19th-Century technology, so it was obvious what to do.
But once I had the Taco valve hooked up to the rest of the boiler circuitry, I couldn't tell if it was working. I'd energize it and the connection would trigger a spark, but then nothing would seem to happen. Unlike the Honeywell valves, which all contain little geared motors, there was no noise. But then I realized that the valve actually was working; it was just extremely slow. It took a full minute or two for the valve to activate once it had been commanded to do so. In the context of a heating system, such delays aren't a problem, but it still seemed weird. So did some research and found out that these Taco valves use something called a "wax motor." Energizing them amounts to electroresistively-heating wax. The wax expands, drives a plunger, and the valve opens. Such motors are always slow and silent. Their chief advantage (beside the minimal moving parts) is the fact that their load is not an inductive one, and so they create less electrical noise in a busy room full of robots.
Throughout the day the weather became increasingly cold, falling well below norms for this season. There was also a wind and enough snow for there to be blizzard-like conditions, although this consisted mostly of the continual rearrangement of a light accumulation.
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