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homemade pressurized fluid supply
Saturday, November 26 2005
This evening Gretchen and I watched a Tivo'd episode of Nova about the domestication and evolution of the domestic dog. We all know that dogs originally came from wolves, but this show helped amend a lot of my assumptions about how humans have altered dog evolution since then. It's easy in our present society, for example, to assume that dogs have always been selected for their appearance above all else. But, as the show made clear, the importance attached to appearance in dog breeds is a relatively recent development, dating to the rise of the middle class in Victorian Europe and America. The appearances dog breeders then tried to maintain had originally developed as side effects over the preceding millenia as people selected for useful traits. The Saluki, for instance, is now bred to retain its long snout, narrow waist, long legs, and deep chest. But our best theories tell us that all of these traits are the result of breeding by ancient Egyptian hunters wanting one thing: speed. The modern obsession with appearances would be as logical to those hunters as them buying a nice looking furnace would be to us.
More fascinating still, traits such as floppy ears, curly tails, and patchy coloration, none of which are found in wild wolf populations, are probably all side effects that come from breeding against aggressiveness. An early 20th century experiment in Russia to breed gentle foxes yielded a completely unexpected result: floppy-eared patchy-colored foxes that barked. The thinking is that aggressiveness comes from adrenaline, and if your breeding happens to favor individuals that don't make many of adrenaline's chemical precursors, this will affect other things such ear stiffness and melanin. The original breeders of Labradors didn't set out with a goal of creating yet another floppy-eared dog; this is a side effect of the breeding for their working traits. Now, of course, breeders catering to suburban soccer moms care only about appearances, and while your Golden Lab might win awards at a dog show, you might not actually want to take him hunting.
I spent most of the day injecting antifreeze into the plastic hoses that provide the four parallel hydronic loops through the basement slab. Each of those hoses is a half inch wide and I was curious how much total volume they would contain. The basement slab is fifty and a half feet long and if each of those four loops went up and back across it once, that would come to a little over 400 feet of hose. According to the chart on the Cryo-tek antifreeze bottle, 400 feet of half inch hose holds about five gallons. Using the system theoretically described the other day, I injected two gallons into the slab without difficulty, siphoning out the old stuff from the other end of those plastic hoses in equal measure to what I was adding. Then I figured that if I'd gone to all this trouble setting up an elaborate injection system (involving a hose running up to the first floor) why not inject more than just two gallons of antifreeze? So I drove to Home Depot and bought four more gallons, along with a 4.4 gallon hydronic expansion tank. I intended to make a tool with the expansion tank that would allow me to inject the old hydronic fluid (which is about 25% antifreeze) back into the system under pressure, thereby avoiding the usually-inevitable addition of fresh makeup water (which, of course, contains no antifreeze).
After adding all six gallons to the slab, there was still no sign of the antifreeze (which happened to be colored blue) in the translucent hoses coming up out of the slab. I added three or four gallons of the old hydronic fluid behind the new antifreeze and, if there was any trace of blue, it was faint. Evidently each of those four loops go back and forth across that slab at least twice, which would suggest a slab fluid volume of at least ten gallons, not five.
I spent much of the latter part of the afternoon and into the evening making that tool for injecting fluid into the hydronic system under pressure. The idea was to turn off the fresh water makeup plumbing and substitute a pressurized cannister of old hydronic fluid in its place. The cheapest pressurizable cannister I'd been able to find that easily attached to conventional plumbing was that expansion tank. For it I made a piece of half inch plumbing with three half-inch female threaded adapters. One of these was for the expansion tank's single connection and the other two were for hose taps.
After I'd built this tool and tested it for leaks, I gave it a test drive. I bled all the air from the expansion tank's air nipple (something that is never done when using the tank for its intended purpose). Then I filled it with water through one of the bibs, stopping occasionally to bleed more air from the nipple so I'd have room to add more water. After several such cycles no more air could be bled, so I closed the fill tap and then opened the other (output) tap, which I'd connected to the hydronic system via another hose. After using a motorized air pump to force 20 psi of air into the expansion tank's air nipple, I switched on the hydronic pump and had it take whatever it needed from my tank (instead of from the household fresh water system). The first time I ran this system, I was amazed and delighted that it took nearly four gallons of fluid from the tank. That was almost four gallons of recycled hydronic fluid which, because it contained 25% antifreeze, was worth about $11! (I have five or six more gallons of 25% antifreeze still on hand that I'd hate to throw away, but all the hydronic pipes are full.)
I know it's difficult to follow me when I write about these sorts of things, so I drew a diagram (using Microsoft Visio).
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