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Just Don't Get Modcon Boiler Pump Charts!
Can someone explain to me what the delta T rise on a modcon boiler circulator sizing chart relates to? For example, a Lochinfar 55 reads 3 gpm at a 35 degree rise, 4 gpm at a 25 degree rise, and 5 gpm at a 20 degree rise. Rise of what? The water is circulating in the primary loop at a rate that hardly allows for any temperature drop from one end to the other, and this is temperature drop, not rise. Also, the circulator they send with the boiler will move water thru the primary at 9 gpm, not 5, never mind 3! How doI "design" for a 35 degree delta T rise? and what is with the oversized circulators? Do i need to worry about any of this, as long as i am always moving a minimum of 3 gpm thru the heat exchanger?