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And so we'd take it from there. I'd try to coax more information out of the guy. What was on the nameplate? Oh, there was no nameplate? How about on the motor? Could he get the horsepower rating? Can't read that either, eh? OK, how about the size of the flange? Or the length of the circulator from one end to the other? And the centerline between the flanges?
So I'd think about that marble. Which way would I go if I were rolling through the pipe? I liked to think of my marble as being large enough to touch the inside walls of the pipe. Big enough to feel the friction as its sides rubbed against the insides of the pipes. Friction loss. Delta-P. And there was also flow rate to consider, of course. I knew by this time that heat traveled on flow like a passenger on a train, and the more flow there is, the more heat there can be. You could see all of this on that beautifully simple tool, the System Syzer. The late, great Gil Carlson had invented the System Syzer. On it, he showed the normally used maximum flow rates for copper and iron pipes of various sizes. You could design for flows beyond these, of course, but you'd probably wind up with excessive pressure drop and velocity noise in most cases. If you stayed within Gil's limits, however, you'd be safe. For instance, Gil's wheel told me not to try to move more than 4 gpm through a 3/4-inch pipe. The folks who make baseboard convectors show that very same limit, by the way. That's good enough for me. If I needed more than 4 gpm, I'd move up to a 1-inch pipe, which can handle up to 8 gpm.
When a contractor would call and tell me about the broken red circulator, and he didn't have any other information, I'd ask him what size pipe served the circulator. I'd figure that the circulator shouldn't try to pump more than that pipe could handle. Here are the limits I'd use:
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Often I'd be able to look in the old B&G catalogs and find what I thought might be the right one for the job, but this was making the big assumption that the circulator that was there now was the right size for the job, and that's a big assumption to make. After all, the circulator was broken, and maybe the reason why it was broken was because it was the wrong size.
| Dan Holohan - [Intro] | [Email] | [Website] |
| The views expressed in this article are those of the individual author and do not necessarily reflect the views of the management or staff of MasterPlumbers.com |
