Got a system that has two 4-ton cooling systems that have separate ducted returns and which have a common supply.
The controllers are networked together currently, although they can be made to operate as stand-alone. The problem has been an extended history of intermittent low pressure alarms. The networking can manage up to six total units...N +1, with the last unit in the series being the backup unit. The master controller can also use stages in other units for multi-unit sequencing and/or capacity assist.
In this case, the "backup" unit is always operating in the capacity assist/sequencing mode because there is a full load of heat.
In the interest of assuring the best solution, I am going to test the static pressures and clock the blowers today, since it is my opinion that the heat load in the room is nearly maxxed.
Meanwhile, I made a change or two in the programming--I made both deadbands to be 2.0 degrees and I eliminated the changeover to backup units when certain alarms occur(specifically the Low Pressure condition). That way, the other circuit in the problem machine should continue to operate and of course, the blower whereas they were being shutdown.
When I test the static pressures, should I test individual supply ducts and then also take a reading after the two supply ducts join? Which of those two readings will best reflect the design pressure? I'm planning on contacting the manufacturer to see if they even are aware of the supply duct as built.
Hint--the issue is not a lack of refrigerant in the circuit. It could still be an intermittent wiring problem, but no amount of control wire-wiggling or wire-nut wrestling has caused a blip yet... And just as an aside, I disabled the pumpdown feature. It can bang on against a full load of refrigerant for all I care (yes the CCHs are working).
The air testing I'm doing is just to firm up the design/as built harmony, as I'm also looking ahead to the possibility of actual backup (sale$) cooling. But it would be nice if first I could solve this problem...