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Being a licensed plumber from Ma. who is a CPD with ASPE I convinced my wife that I could heat our swimming pool for a couple of weeks on each end of the season with our 50 gallon, gas water heater.
I purchased a Therma-Flow Everhot RM-10-SP copper heat exchanger and two Taco 110B circulators with 3/4" flanges. One pump goes through the coil, into the water heater on the cold side and is drawn through the hot side and works off an aquastat. The second pump goes through the exchanger (low pressure side) to two 11/2" x 3/4" tees spaced three inches apart on the return side of the pool line and runs on a time clock. There is an auto vent on the top of the exchanger.
For some reason the line through the exchanger to the pool will not maintain hot water circulation even though there is hot water through the coil from the water heater. If it is purged at the pool it will circulate hot and then after a while it seems to stop.
The other more dramatic issue (other than my wife is do home from business this PM) is while the circulator through the coil is on I am by-passing the water heater and getting cold water into the house. This was established last evening 2 minutes into a shower and was verified by turning off the circulator and getting instant hot water.
I realize there is not much to go by but if there is any creative interest in solving my puzzle I wil answer any questions.
On a note to Dan, I have used your Pumping Away on a number of occasions and saved my employer not only financially but in much good will. Thanks.