Hey Guys, question I'm hoping you can help me with. For those following allowing, I installed a Bard 5-ton GV61S1 GSHP in December, open-loop with 6x600' slinkies. Antifreeze is 20% methanol, freezer test shows protection down to 0F. I typically run the unit during the day as necessary to heat a large open space to mid-50's/60's and it hasn't been a problem, even with outdoor temps in the single digits. Pressure drop and EWT/LWT's match up against the manual for this config. All humming along nicely. Last night the outdoor temp dropped into the negatives so I fired the unit up in advance and ran it all night. it worked great all evening and was working when I went to bed. This morning I found it locked out due to low-pressure. I played around with it this morning and this is what I've found- Correct LPS was in-ckt for an antifreeze loop. Room air temp was 38F. Initially, bypassing the switch would not get me any heat, nor cold while compressor ran. Plenty of flow through the loop field as verified in the open loop flow center (15GPM). I put an electric heater at the base of the unit with panel pulled, and my meter on the switch (ckt bypassed). I cycled it back and forth a few times and now I at least get closure for a minute or two before it defaults open. I got the compressor to run long enough on Cooling to get an EWT of 35F and a LWT of 39F and climbing before my meter showed the switch opened, at which point the LWT dropped back down to EWT. Thoughts? Does this sound like a refrigerant issue? Could entering air temp be too low?