I wanted to let everyone know that changing the thermostat cycles per hour (CPH) from “3” to “1” has had a positive impact on hot water production from the desuperheater.  Previously, the best we had ever gotten was ~90F water in the tank.  This morning the tank storing water heated by the desuperheater is at 105F.

So, if our groundwater is coming in at 47F and we heated it to 105F, how much energy did we essentially get for “free”?

A BTU is defined as the amount of energy required to raise one pound of water by 1 degree F.  One gallon of water weighs 8.3454 pounds.  The desuperheater raised 50 gallons of water (417.27 lbs) by 58 degrees F.  Therefore: 417.27lbs x 58F = 24,201 BTUs.  Since one gallon of propane (which is what we would otherwise have to use to heat our hot water) contains 92,000 BTUs, and our burner is 94% efficient (we only get 86,480 BTUs per gallon) we avoided burning 0.28 gallons of propane to heat this water.

It has not been sunny in two days, however, we still have some warm water in the solar tank.  That tank is at 90F this morning.  Doing the math…  80 gallons (667.32lbs) raised by 43F (from 47F to 90F) = 28,694 BTUs.  This avoided burning 0.33 gallons of propane.

In the past 48 hours, the desuperheater and solar hot water system have provided us with the equivalent of (at least) 0.61 gallons of propane for free.  I say, at least, because we have also had our normal usage during that time period… laundry, bathing, dishes, etc., and we still have more in storage.  Neat.

Ed