I'm a new pool owner and my pool has all mechanical valves which I think I've sorted through enough to have half a clue what they do.
The heater I have is a Pentair Minimax NT.
This weekend was the first time I really tried to use the heater. I was successful in getting it to run when I have the valves configured to suck and fill from the spa only. When I changed this so that the overflow would flush into the pool, the heater through a code for the pressure switch, but then seemed to overcome that and turn back on.
My goal ultimately was to heat up the pool a bit. So in my simple mind I thought perhaps it was more efficient to just run the pump to suck and fill from the pool only. At this point the heater would not stay functioning and light for the pressure switch would shut off.
So ultimately I think I've concluded that my heater will not run when I'm only flowing water back into the pool.
In this case it rules out anything upstream of the heater since everything is good when I'm pumping the hot water back into the spa (regardless of whether the spa drain is open, closed, partial). So what is going here? If it were a clogged filter it clearly wouldn't work in spa only mode....so I guess this says there's an issue with my feed line to the pool?