Hi there, We have a Climatemaster Genesis 3-ton water source heat pump, open loop system that takes water from a pond adjacent to the house. The system has ben running okay since it was installed 2.5 years ago but, on occasion, have had to "steal" a bit of water flow from our well by connecting a garden hose to the intake side of the heat pump to get it to keep from locking out. Every time the system has locked out, since it was installed, it's been a code 4 (FP1) on the CXM board. The water temperature from the pond is 40 F and it seems if I can get decent water flow to the unit it runs fine. I'm assuming low GPM can cause low water temperature lockouts, is that correct? Right now, if I don't steal water from the well The two Grundfos pumps (1 in and 1 out) will only cause a reading of 3.5 GPM which I know is low. Accounting for water temps, etc. I think I should try and get somewhere between 7 and 10 GPM. I think 10 GPM should make for a more efficient system all around? Would that be correct? When I start the system, the unit runs for about 5 minutes before going into 2 retries and then lockout. During that 5 minutes the unit is producing heat from the vents but I'm assuming the low GPM might not satisfy the heat pump's requirements, etc. If I connected a small gas-powered water pump to the inlet side of the heat pump and got the flow to read about 10 - 13 GPM would this be a good place to start in terms of starting to solve this problem? This whole December weather thing is really getting in the way of a warm house without the heat pump functioning and the kerosene heaters are getting a little old after 1 week. Any thoughts and suggestions are greatly appreciated.