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Posted by HeatPro on June 13, 2006 at 18:08:16:
In Reply to: Circulator location? posted by Russ on June 13, 2006 at 17:28:36:
There are good reasons for putting a circulator on the return side, even though it is generally the wrong thing to do as in the lesson on series design at www.heatpro.us
A good reason is to provide a positive pressure into a boiler when the boiler is a small-tube (instantaneous-type tankless boiler) that has a hight pressure drop, as many of the Japanese and European boilers. When that is the problem, the circulator pumps into the boiler and away from the expansion tank.
After you find out WHICH type boiler you must apply the circulator to, you will be able to determine where the circulator should be placed. Many piping diagrams of Weil boilers are as loop sub-loop where the circulator pumps water from the main loop into closely-spaced risers from that main loop.
Another way to say it is that using rules of thumb for EVERY situation is equivalent to keeping your thumb under the hammer.