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boiler wiring homestretch
Monday, September 26 2005
I spent most of the day down in the boiler room continuing with low-voltage electrical work, which has occupied most of my solar-related project time for the past week. The other day I'd discovered that all the valves operate on low-voltage AC power, not DC power, and this initially seemed to complicate my plans. In the end, though, all I needed to do was build a rectifier circuit for the parts of the circuitry that really do need direct current power (the controls for the three different relays).
Today I finished the last of the boiler room wiring and confirmed by a series of tests that it was all working correctly. Electrically, all I need to do now is finish the running of low-voltage signal wire up to the solar deck and then I need to hook up two electric thermostats that can monitor whether or not the solar panel is warm enough to heat water for the two applications (slab and hot water heater).
In the midst of all this wiring and soldering (and, almost as importantly, the tidying-up of wiring), I discovered a very small leak in one of the solders I'd made in the solar hydronic piping. Normally failing solder joints leak spectacularly, but this was producing a drop every ten minutes or so, and probably had been doing so for weeks. I couldn't let this situation persist, so I drained the pipes (this involved removing the solar system's expansion tank and one of the valve mechanisms) and then, using an enormous amount of heat, resolder the joint as best I could without actually disassembling it. In the process the heat migrated through the pipe some six inches away and made another soldered joint fail, though this one was holding back a sizeable water pressure which then came pouring out. I wouldn't think it possible for a joint with water contacting it to heat up enough to fail, but I've seen it with my own eyes. Perhaps the pipe ruptured at that joint from the pressure of boiling water vapors that could not escape. By the way, in the case of both of these failed joints, they involved copper soldered to heavy brass valves. This not the first time such solders have failed; it takes a lot of heat to successfully solder such big pieces of metal.
After I finally got the two leaks fixed a broke open a forty ounce bottle of malt liquor to celebrate as I tidied up the rest of the wiring and then cleaned up the boiler room in a way it has never been cleaned under my entire administration.
Here you can see the solar expansion tank, the solar circulator pump (it's green) and the cold water make-up system (in the midground in front of the expansion tank). The indirect hot water heater is the massive blue thing in the back.
The bulk of the solar "plumbing logic" viewed from below. You can see three or four electrically-controlled valves in this picture.
The solar controler, with the mode rotary switches and instructions for what the modes mean.
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