Circulation Pump (DHW)

Calculating a decent estimate impact of continuous circulation would require a detailed analysis of the entire piping system including pipe diameter, flow rate, insulation level, pipe location, etc.  This is well beyond the scope of OptiMiser’s DHW model and most audits.   I also suspect that the potential results would vary too widely to put in a simple multiplier.  I’ll put it on our long term wish list.  If you are aware of any good research on the matter, please send it our way.

In the mean time,  if you want to play around with your own estimates, the best way to simulate the effect would be to decrease the rated EF of the water heater, while leaving the recover efficiency unchanged.  The constant re-circulation has the effect of increasing the tank UA, which decreases the EF.