Within the temperature range

Gas-powered kitchen ranges that vary in width from 24 in. to 48 in. The standard kitchen range is 30 in. wide.

Automatically measure temperature at up to 1700 points to ensure safety compliance with ANSI Z21.1 “Household cooking gas appliances” (American National Standards Institute, www.ansi.org). Develop a test chamber flexible enough to accommodate all range sizes.

• Omega Engineering: thermocouples. www.omega.com.
• United Electronic Industries: Ethernet-based data-acquisition modules. www.ueidaq.com.

Whirlpool (www.whirlpool.com) designs and manufactures household appliances, including gas-powered kitchen ranges, under several brand names. All models must comply with industry standards for safety, including standards covering how much heat a range can emit.

To comply with ANSI Z21.1, technicians must test new ranges for external temperature. In the past, two or three technicians would manually make measurements by connecting each of 900 thermocouples to a temperature reader, one thermocouple at a time. A single set of measurements required several hours of a technician’s time to set up and make. Later, engineers developed a semi-automated system where a technician could connect 50 thermocouples to a datalogger at once. That cut technician time to about 1 hr, but was still rather time consuming.

Today, technicians at Whirlpool’s Edgewater Technology Center in St. Joseph, MI, including Johnny Isaacs, use a test booth that simulates a kitchen and lets them set up 1700 thermocouples in 2 min. The faster setup doesn’t reduce the actual test time, which is defined in ANSI Z21.1, but it frees technicians to do other jobs while the test runs.

Up to 1700 thermocouples—connected to 16 data-acquisition modules—monitor the temperature around a gas range during a product evaluation.

For a 48-in.-wide range, the system uses all 1700 thermocouples installed in the booth. For smaller ranges, the outermost thermocouples aren’t used. PC software, written by senior technician Kirk Boyd, lets technicians select which thermocouples to ignore for the smaller ranges.

The thermocouples connect to 16 data-acquisition modules, each of which can accommodate 108 thermocouples. A test takes 9 hrs to complete. Technicians run the oven in cleaning cycle, which runs the oven’s internal temperature to 860°F, for 4½ hours. If at any time the thermocouples closest to the range detect an outside temperature higher than 194°F (117°F above the lab’s 77°F ambient temperature), the system will notify technicians to end the test.

If the temperature remains within tolerance, the system records the last temperature measurements before the cycle ends. A technician then lets the oven cool for 30 min, which drops the chamber temperature low enough to enter the room and open the oven door because the oven automatically locks its door when internal temperature exceeds 600°F. This action tests that the oven’s automatic locking works. Then, technicians close the door and repeat the test. This time, they turn on the burners (four or six, depending on the model) 3½ hours into the test.

“Flexibility is key,” said Isaacs. “As Whirlpool’s ranges went beyond the standard 30-in. width, we needed a flexible test booth. We can’t have a dedicated test booth for every range size.” Technicians use the test booth nearly every day because of the number of new products in development.