Just opened the pool last week, got the water balanced, turned on my SWG, and then went to turn on my Heat Siphon heat pump and it wouldn't start. I got it last year and it worked great all last summer. I called the company and the woman told me it's most likely either electrical connection or water flow. All the circuits are on, so I assume it must be insufficient flow? The pressure gauge on my DE filter tank is currently reading 12, which is pretty normal. Figuring that maybe it was a little high, I backflushed and added new DE and the reading went down to 10psi, but the heater still wouldn't kick on.
The next step is a service call, unless someone on here has something else I could try. Again, the heat pump is only one year old and worked great all of last summer. Thanks!