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Posted by HeatPro on April 13, 2005 at 22:33:24:
In Reply to: New Radiant Zone Overtemping Boiler - HELP!!! posted by Dave Tzeutschler on April 13, 2005 at 19:31:31:
Yes, the zone is too small to turn the burner on to heat just the one zone, as it hits the high limit quickly. There is no sense to provide 100,000 btuh to heat a 5000 btuh zone (the bathroom output is 1/20th the input of the burner.) There is no way you can have the mixing valve feed the entire water of the house through the little zone. You have a control planning problem.
You probably have the zone as a separately-pumped circuit from the boiler supply and return manifolds as part of a multi-zone system; although you haven't described how it is connected.
Use the bathroom thermostat to run the circulator or open the zone valve to the tubing of the bathroom without turning on the burner. As other zones will fire the burner for their heat, there will be enough operation of the burner over the hour for the other zone operations to periodically feed hot water to the bathroom zone. The mixing valve will limit the water temperature to that circuit.