In which case Delta-T would provide insight?"
Delta T is a piece of the puzzle. If EWT is good LWT water temp too low is going to be flow or refrigerant charge. You shouldn't find a proper LWT when you're tripping on Low pressure.

As problem seems to be intermittant, I'm leaning towards a water problem. Refrigerant problems usually don't cause intermittant lock-outs.
If I had to guess flow is impeded or bleed off is inadequate.

If earthheat is still around: how old is system? How often is it locking out? can you tell us your entering and leaving water temps? Do you clean filter everytime system locks out? We are talking heating not cooling right?
j
The system is a new installation this winter. The filter system is a Lakos Sandmaster with auto purge. The problems occurred prior to installing the sandmaster. There is also a 40 mesh cartridge filter installed. This was believed to be the culprit in the beginning due to a higher mesh screen was installed before. The flow has been verified with a flow meter that is installed on the bleed. I get the required 9 GPM and to ensure this I've increased the pressure on the constant pressure pump. I don't believe the issue is a water flow issue.

I have installed gauges and I have the following;
EWT- 45.6
LWT- 40.0
2 GPM Bleed
9 GPM flow rate
Load EWT- 103
Load LWT- 111.1
Suct- 102 PSI
32deg SAT, 48 deg ACT, 16 deg SH
98.6 ACT, 120 SAT, 22.4 SC
Compressor AMP 11.1
231 VAC Line
26.2 VAC Control
I added 17 oz of R-410a to initially drive the SH down to 6.7 degrees. This allowed the heat pump to last a week and then went into FP2 fault. After a restart, this lasted less than a day. I can't find any refrigerant leaks or oil spots, but have erroneous refrigerant alarms on my leak detection. I feel this may be a leak, or a malfunctioning TXV? I'm going to pull the refrigerant and see how much I have in the system after I do another thorough look. The system came this way from the factory but I looked at the water issues first.
Disch- 420 PSI

How long did you let system run before checking charge? Did you disable DSH during tests? Are you the installing contractor?
J

I'm the installing contractor and I did disable the DSH before taking measurements. The run time was substantial due to heating up the accumulator tank from 72 degrees to the 100 deg mark. I did a leak check again today and found no leaks. I removed the charge and found 4# 8oz of refrigerant. I believe the problem is the TXV, I'm replacing that and the dryer as soon a I receive the parts.

What was the factory charge?

Your flow rates and temperature differences are right on the money so you most likely have a faulty FP1 sensor.

Climatemaster has continuing issues with these it seems. There was a big problem in 2006 and they changed sensor suppliers so I was told. The resin encasing the sensor breaks down from thermal stresses and lets in condensation. The condensation fools the sensor and poof! FP! fault. Happens for FP2 as well. A real pain.

To check it out for sure, bypass the sensor by snipping the grey sensor wires and joining them together towards the board. Then the computer should think the sensor is warm. If it stays running, then it's the sensor. If you start to frost up somewhere then you have a fridge problem.

Good luck