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Posted by Joe Brix on November 30, 2005 at 08:53:33:
In Reply to: Re: To HeatPro and Joe Brix posted by Dave on November 30, 2005 at 06:13:57:
: The zone circulator controls do not need to start the boiler burner. An outdoor reset can make the buffer tank warm enough to provide heat when needed to each zone.
: +++How I understood the way my system currently is controlled is as follows: We have a Taco controller SR506 (I believe). Whenever a zone circ is running, the boiler pump also runs. The boiler itself just seems to fire when the operating temperature of the water in the boiler loop is below about 150 degrees. Once it reaches its high limit, which it does fairly often, the boiler shuts down, but if a zone pump is still running, then the boiler pump continues to pump until the water temp drops below 150, and then the boiler fires again. There are temp sensors in the header next to the boiler inlet and boiler outflow. So it seems like the boiler fires totally independently of the the circulators. I would assume that the tank wouldn't change anything....water would circulate in tank/boiler loop whenever a zone is calling for heat. Once the temp of water gets below 150, boiler will fire. Once water temp gets to 180 (operating temp), burner would shut off.
: Does that make sense?
Yup, that's right. The only thing I don't like about this set up is having the boiler in the primary loop. I would also make the boiler and it's circ a secondary loop off the buffer tank loop. Boiler's circ would only run when the boiler is firing as it's putting BTU's into the buffer.
I feel after the buffer tank has been brought up to temp, the boiler will cool off and start to suck BTU's out of the tank if you run the boiler circ as part of the primmary loop.
I think I listed this link before for you by
John Siegenthaler:
http://www.pmmag.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2379,78589,00.html
Will require an extra circulator, but now you can have a large differential along with the outdoor reset, so the boiler will run longer but less frequently.