ACHRNEWS

Modular Indicators Do Away With Maze of Wires

June 5, 2000
Rack's Electrical Cabinet Keeps it Simple The challenge of refrigeration rack systems goes beyond dealing with mechanical malfunctions. There is also the electrical enclosure cabinet with its maze of indicator lights, switches, and circuit breakers, all individually wired.

That was the focus of attention as Tyler Refrigeration set out to redesign the electrical enclosure cabinets for its racks.

"We wanted to streamline assembly, improve quality, and make servicing easier for our customers," said Mike Harvey, design engineering manager for Tyler's Mechanical Systems Division.

The company shared its idea with the Refrigeration Systems Group of Johnson Controls.

Among components chosen for improvement were status indicators for compressors and refrigeration circuits.

From the start of development, goals were to:

  • Simplify assembly and servicing by using quick connections to replace hard wiring of components, and having more orderly wireways with fewer control wires.

  • Conserve space. "Module size was a big consideration," recalled Tyler design team member Andrew Bopp. "Customers are always asking us to make a smaller total package.

"A typical rack control panel electrical enclosure may require more than two dozen of these modules. We had to keep them compact."

Each circuit and compressor module has a 17Â¥8- by 5-in. face plate backed by a printed circuit board that integrates all LEDs, circuitry, and switching. All hookups are by way of Phoenix connectors - three for the compressor module, and a maximum of five for the circuit module. The connectors enable the use of wire harnesses, designed to minimize assembly time on the production lines and reduce potential for wiring mistakes.

The modules fasten to the front panel of the rack's electrical enclosure with two screws. If a module fails in the field, the technician can unscrew the module panel, disconnect the unit, and plug in a replacement.

The absence of wiring for indicators inside the cabinet leaves the door interiors clear for posting operations and service information such as wiring drawings, refrigeration and electrical schedules, and defrost schedules, noted Harvey.

The arrangement includes two modular control indicators from Johnson. The refrigeration circuit modules with LEDs indicate whether a circuit is in the refrigeration or defrost mode.

The compressor modules with LEDs show when a compressor is running and whether it is experiencing oil failure. Each type of module includes a circuit breaker providing built-in over-current protection for the control circuit.

For more information, contact Johnson Controls, Inc., Refrigeration Systems, 1000 Cobb Place Blvd., Suite 200, Kennesaw, GA 30144; 770-427-9808; and/or Tyler Refrigeration Mechanical Systems, 2275 N. Highway 77, Waxahachie, TX 75165; 800-845-0821.