I had a pool company winterize my pool (pulling plugs, etc.) I put all the plugs back in, got my water chemistry right, then fired up the hot tub. The valve actuators automatically turned (though I don't know exactly which position they are supposed to be in). The heater kicked in... and the water at the heater was steaming hot. However, the water coming into the spa was luke warm at best... then tended to turn cold. The water never went up in temp, even after running the heater for over an hour. I was concerned about hurting the heater, so I did not continue operating it. I did repeat the procedure the next day with the same result.
As a side note, the pump for the heater and cleaner is the same... and the cleaner works fine. I have backwashed the DE filter several times. No change.
Any idea why the water in the spa won't heat up?