Compressor monitoring System

[Cyril Silberman]

Need advice, I have just completed installation of a data collection and monitoring system in a marine vessel. One of the monitored systems is the a/c compressors and the galley refrigeration. All a/c compressors are water source heat pumps with conventional hermetic compressors. The refrigeration is conventional air to air.
I have provided one thermocouple for each unit compressor and attached it to the suction line adjacent to the charging valve, I am reading temperature but I am struggling to devise a logic program that will deliver useful information to log history. The intent of this system is to assist in preventative maintenance and to see trouble coming before the vessel is cruising. I also log on off cycles, water temperature, inside air temp, etc.
Any suggestions would be appreciated, even if I must add additional probes. I am not prepared to cut into the existing system and add pressure switches to the ***** lines.
Thanks, Cyril

[chemi-cool]

With too many probes you will be facing more problems.

I would monitor the power draw by each compressor and prepare some table of the relation between ambient and power draw to let you know when you are out of safe zone. That will be good for air\air units.

For air\water units the power draw is more stable.

A sudden drop in power draw can indicate that evaporator fan is not running or icing.

too many parameters can confuse you and not always indicate a problem.

[Brian_UK]

I wonder whether monitoring the compressor discharge temperature might prove more useful.

An upward trend may indicate a shortage of refrigerant and the resulting increase in superheat.

[goshen]

Hi
you would probably be better adding 2 pressure probes on the check valves ,
you would be able to convert pressure into temp and monitor entire system accuretly!