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Posted by Boilermate on July 17, 2008 at 11:54:34:
In Reply to: Maximizing Efficiency of Indirect Water Heater? posted by Sean on June 25, 2008 at 16:48:23:
When you say "indirect" I assume you mean a BoilerMate, SuperStore, or similar system. In such an arrangement the boiler heats the water that goes thru the coil and heats the dhw.
I'm not sure it makes much of a difference if you have a fixed differential aquastat. You would draw less hot water if it was set higher, but the boiler would have to warm up longer before it began heating up the tank.
For max efficiency it would seem that installing a variable differential aquastat and setting it with a wide differential (say call at 110 and satisfied at 140) would do the trick.