An Easier Parallel Boiler Connection?
Posted: Fri. Jul. 10, 2009 1:14 am
In reviewing the AHS parallel boiler configuration and looking at my current oil-boiler configuration (looks just like the right-hand side of the AHS diagram), I'm wondering if I can add a Ka-6 in parallel with my existing oil boiler by simply adding the AHS-indicated "new check valve" between the Ka-6 and oil burner supplies (allow flow from coal boiler toward oil boiler, up to radiant heat but not back toward Ka-6) and installing a zone-valve (with limit contact) on the return to the oil-burner. The zone-valve on the oil-burner return would remain closed when the Ka-6 is operating but open when the Ka-6 is below operating temperature ("failed-over to oil" condition) to allow return to flow through the oil-burner. As a precaution the oil-burner control power wouldn't be allowed to "make" unless the zone-valve limit contact was closed. My existing return pump is located prior to the oil burner, and the Ka-6 return would be plumbed in parallel with the oil-burner return. This setup would look just like the AHS parallel-boiler diagram, except the "new circulator" pump would be eliminated and a zone-valve (with limit contact) would be added on the oil-burner return. Plumbed this way the Ka-6 wouldn't constantly heat the oil-burner (and send hot air up the chimney), and the oil-burner wouldn't heat the Ka-6 when it's shut-down. The downsides would seem to be cold-starting the oil-burner at the start of failed-over operation, and pumping water through the coal boiler when shut-down (wastes heat) which I wouldn't expect to happen more than a couple times per year. At the end of the winter season I could close a manual valve on the return to the coal boiler to eliminate pumping oil-burner heated water through it during summer months.
What drawbacks exist with this scenario? What am I missing? Any advice would be appreciated. Thanks in advance.
http://www.alternateheatingsystems.com/boilers_in_tandem.htm
What drawbacks exist with this scenario? What am I missing? Any advice would be appreciated. Thanks in advance.
http://www.alternateheatingsystems.com/boilers_in_tandem.htm