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Posted by HeatPro on April 29, 2006 at 23:05:20:
In Reply to: Re: adding pump delay posted by Dave on April 29, 2006 at 08:35:00:
The water temp at the gauge gets to 190F or so, but the tubes of the boiler probably get locally hotter temps so the clanking comes from the boiler tubes being slammed with cavitation of collapsing steam. That is the reason for the ErgoMax install, but that doesn't help when the water stops and excess heat happens in the boiler tubes. It isn't good to shot-peen the tubes with water several times a day.
You can get a delay-upon-off timer from HVAC suppliers that can let the circulator run a while after shutoff that can act at the circulator relay.
http://www.issc-kanson.com/hotprod.htm