The heat pump installation is an education. As is becoming usual for Surna products, the issue is the flow rate. A half horsepower pump isn't enough?! So we're going with a full one horsepower waterpump to ensure flow to the unit is on point.
Frankly, even a cursory examination of the water heated evaporator core shows that it's suspiciously small, as are the lines running to it. If the- unlisted in the specifications given- restriction it places on flow is great enough, no amount of pressure will overcome it.
If a one horsepower water pump pushing water through 1 1/4" ID spa line isn't sufficient, I'm going to be an unhappy camper.
Before you ask, here's the specs on the downstream manifold; same 1 1/4" inlet, or an inlet surface area of 1.227 in². Manifold has three exits, all 3/4", or .441 in², times three = 1.325 in², bigger than the inlet and thus should not present a big restriction. We shall see...