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with just a circ pump, there is virtually no heat transfer from the pump.
A circulation pump can most defintitely heat the water 10 degrees.
Spahappy,I read about the mode options in the manual but it doesn't explain the differences very clearly. With my tub set to run in the Standard mode, the circulator pump is running in warm weather without the word "Heat" visible on the control panel so I'm assuming that a thermostat is telling it to stay off. I'm curious as to how the Sleep mode is going to be different ? Setting the circulator cycles for the cooler time of day settings is a great idea. I'll make that change tomorrow. Is there a trick to keeping clean water with two-four hour circ times? I went from 6-4 during the winter months and before long, my water started giving me problems.Mike