Desuperheater Issues

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Please explain more, Are two tanks necessary for additional volume or is there more?

 

Buffer tank is to seperate water heated by DSH from water heating by elements or burner in finish tank.
It is the way to ensure the best yield from your DSH.
j

 

Value of two tanks

Here is the deal: Simple superheating, R410a (unless we go to new refrigerants capable of over 400 psig) will fairly easily raise a hot water tank temperature to @90 - 100, degrees F, IF THE HEAT PUMP RUNS LONG ENOUGH, and if they have the right designed controls.

If the available heat or condensing temperature in the condenser coil (winter mode) is UNDER that temperature, then hot water in the primary tank will transfer back to the desuperheater coil (if the water circulating pump continues to run), in other words, you will get no further hot water heating, but it doesn't necessarily hurt the heat pump. It simply can't go any higher.

The physics principle is this: heat travels from a hotter surface to a cooler one.

So, the heat pump has to be in top tune or efficiency, and the primary tank, unless you have a LOT of tonnage, can only get so far, WHEN IT IS RUNNING. This is especially true of units under 3 tons.

The second tank is essentially this: You have 58 degree incoming water or less, you preheat heat it to 86 - 95 degrees in the first tank from the heat in the heat pump, thereby getting the maximum heat transfer easily, and now you feed a second electric tank in series,.80 - 90 F degree water instead of 58 degree water. The second tank "satisfies" earlier, and recovery is much quicker, effectively increasing your overall capacity, AND SAVING ENERGY. You have used less electriciy or natural gas.

Theoretically if you use the new HEAT PUMP hot water tanks as tank # 2, AND IF THEY ARE RELIABLE, they shoud be VERY efficient because the new GE's and AO Smiths use only 680 watts at 230 volts instead of 19 amps.

Think about that. Those new heat pump water heaters are not dependent on the house heat pump operating. Incoming water can be 30 degrees F or 100 F.

Warning: all heat pump water heaters sold are not made alike. One brand, for example uses more expensive porcelaine to insulate the tank and cover the heating tubes. I will not mention the brand.

Look carefully at the warranties. Find out how they are made.