Henningsen Cold Storage Co., Hillsboro, Ore., works constantly to reduce energy use in its facilities. Companywide energy consumption per cubic foot of cold storage is consistently well below the industry average, according to the firm. With energy being the Henningsen's second-highest expense, improvements in energy use directly result in higher profits.

To further improve the facility's energy efficiency, Pete Lepschat, Henningsen's assistant manager of engineering services, has come up with an idea for monitoring refrigeration system efficiency after reading the specifications for a wireless system from Comark Instruments in Beaverton, Ore. He plans to use the Comark RF500 wireless system with model RF512 Comark transmitters inside a -15°F (-26.1°C) freezer area with 10 refrigeration evaporators. Though not yet in place, the Comark RF500 system at Henningsen's Cold Storage is expected to be installed and reporting by mid-September.

Lepschat's objective is to improve energy efficiency by having ready access to data on how the evaporators were performing. To accomplish this with RF500, he will place the transmitter's integral sensor near the input of the evaporator, recording the air inlet temperature. He will place a sensor from one of the two wire probes that report to the same transmitter at the outlet end of the evaporator and the other sensor 100' away in the same room. The open/closed circuit sensor (a modified magnetic door switch mechanism that also reports to the same transmitter) will monitor the status of the evaporators' liquid refrigerant feed solenoid. The RF512 will be set up to signal and alert when any of the monitored temperatures are unacceptable or the solenoid "on" time exceeds the desired duty cycle, either of which can indicate an early sign of system problems.

Although Lepschat has been able to monitor these factors prior to deciding to incorporate a Comark system, it is not as easy. According to Henningsen, the company needs to use various instruments, manually collect and combine the data, and then analyze the results.

The RF512 can record up to three temperatures plus a single on-off status. The transmitter time-stamps and logs data, and it notifies users via e-mail or text messaging when set parameters are exceeded. With the RF500 wireless system, all relevant readings are logged into a database with a single transmitter. Each RF512 transmitter can be named with a description that represents a specific evaporator in a freezer, which will allow the user to see all data for one evaporator by simply selecting its description in the database. The RF500 software also builds multi-graphs, so the user can select a set of evaporators and open a quick visual in graph format to see trend variations and notice whether any are moving out of line.