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Posted by HeatPro on August 18, 2005 at 20:32:43:
In Reply to: Swapping Taco 007 for 0011 circulator posted by Jeff Gray on August 18, 2005 at 11:26:09:
Who is "The company I'm getting the boiler from says this is a bad idea."? If it is the manufacturer of the boiler or their rep, I'd suggest following their advice. I'd definitely follow them exactly if it is a copper-tube boiler.
A potential problem with a boiler is not providing enough water flow through the boiler when some of the zones are open. This is less of a problem with boilers that contain a great deal of water, as the large mass of water can absorb some heat for a while so it doesn't shut down immediately or worse - make steam from residual heat in the exchanger. There are some solutions for small-water-content boilers. There would be less need for typing here if you had identified your boiler type so a shotgun approach wasn't necessary to cover all types of boilers. To shorten the process, it is best to have an undiminished flow through all residential boilers as they are small and have just a few gallons of water in them. Having a 150,000 btuh fire and only 30,000 btuh of water flow to serve a few open zones can give a boiler fits. A large bypass with a circulator running water through a primary loop at a predictable rate is a benefit to boiler and circulator longevity and performance. Taking supplies and return manifolds teed off a primary loop with another circulator feeding zone valves from that does not diminish boiler water flow, so is a concept suggested by most of the boiler company engineers to prevent problems.
If you can identify which boiler type, whether cast-iron, steel, or copper-tube you are going to use and its water content, more definite suggestions can be made. A universal problem on the net is that unfamiliarity with all types makes the questions appear to assume that all boilers are the same - they are not.