Electric Class B Cabinet Oven for Soils and Aggregate Sample Thermal Processing

The project required a compact batch oven for controlled thermal processing of soils and aggregate samples in pans and bowls as part of transportation materials testing activity.

APPLICATION REQUIREMENT

• The project required controlled batch heating of soils and aggregate samples.
• The oven had to support a laboratory environment handling sample pans and bowls rather than large production fixtures.
• The batch format had to accommodate varying sample quantities and loading arrangements within one chamber.

WORK CHAMBER / LOADING REQUIREMENT

• Required work chamber: 55 in W × 30 in D × 60 in H.
• The loading arrangement had to support shelf-loaded samples across multiple elevations.
• Two 100 lb capacity shelves were included for flexible pan and bowl placement.

OPERATOR / ACCESS REQUIREMENT

• The oven had to allow front loading and unloading through two swing doors.
• The 12 in stand had to position the chamber at a practical working height for routine lab handling.
• Loading practices had to preserve airflow passages through the chamber.

QUALITY / CONTROL REQUIREMENT

• The customer required repeatable sample processing within the stated operating range and work-zone uniformity.
• The process needed straightforward local control and visible operating status for day-to-day laboratory use.
• The oven had to support consistent handling of batch sample loads without forcing a single fixed load arrangement.

SAFETY / PROCESS BASIS

• The application used a Class B load basis.
• The process basis did not allow VOC-bearing loads.

SITE / UTILITY REQUIREMENT

• Required electrical service: 208V / 3PH / 60Hz.
• Design elevation basis: less than 1,000 ft.

The project required controlled low-to-moderate-temperature forced-convection heating suited to batch sample processing in pans and bowls.

TEMPERATURE REQUIREMENT

• Operating temperature basis: 140°F to 230°F.
• Maximum temperature basis: 350°F.
• Required work-zone uniformity: ±10°F.

AIRFLOW / HEAT-TRANSFER REQUIREMENT

• Airflow direction basis: full horizontal airflow.
• Estimated chamber air velocity through the work zone was approximately 96 FPM.
• The airflow had to provide even convective heat transfer across shelf-loaded samples.

HEAT-INPUT REQUIREMENT

• Heat source: electric resistance heat.
• Installed heat basis: 12 kW total.
• Heating arrangement basis: one heater bank built from twelve 1000 W elements.

VENTILATION REQUIREMENT

• Exhaust basis: non-powered exhaust with a dedicated fresh-air opening.
• Process classification basis: Class B.
• Volatile load basis: no VOCs allowed.

CONTROL / SEQUENCING REQUIREMENT

• The thermal process used a dedicated work-area temperature controller and separate excess-temperature protection.
• Documented operating sequence:
• Start recirculation fan.
• Turn on heater bank.
• Run at desired set point.
• The heating circuit shut off whenever required safe operating conditions were not met.

COOLDOWN REQUIREMENT

• The recirculation fan remained in operation during cooldown.
• Fan shutdown was delayed until oven temperature fell below 250°F.

To satisfy those requirements, Precision Quincy configured the project as a 40D-350 electric Class B cabinet oven with full horizontal airflow, a side-mounted control enclosure, and a floor-standing cabinet arrangement with a 12-inch stand.

OVERALL CONCEPT

• One electric Class B cabinet oven.
• Compact front-loading batch configuration.
• Shelf-loaded work chamber sized for sample pans and bowls.

HEATING ARCHITECTURE

• Heat source: electric resistance heat.
• Total installed heat: 12 kW.
• Heating was provided by one heat bank built from twelve 1000 W elements at 208V.
• Heater power was controlled through a solid state relay with a backup contactor.

AIRFLOW ARCHITECTURE

• Airflow pattern: full horizontal airflow.
• Recirculation system used a 12.19 × 4 RB fan assembly delivering 1,200 CFM at 2 in. W.c.
• Recirculation fan motor: 1.5 HP.
• The chamber included a fresh-air opening and 6 in × 6 in exhaust outlet.

CHAMBER / SHELL ARCHITECTURE

• Internal work chamber: 55 in W × 30 in D × 60 in H.
• Wall system: 2 in thick insulated construction with 2 in of 6 lb mineral wool.
• Interior material: unpainted aluminized steel.
• Exterior finish: Traffic Gray (RAL 7042).
• Control enclosure finish: Gray (ANSI 61).
• Approximate oven weight: 1,450 lb.

DOOR / LOADING ARCHITECTURE

• Two swing doors at the loading face.
• Two 100 lb shelves.
• 3 in typical shelf spacing.
• 12 in oven stand integrated into the floor-standing arrangement.

CONTROLS ARCHITECTURE

• SSI 804 work-area temperature controller.
• Gefran 650L excess-temperature controller.
• Type J thermocouples for work-area sensing.
• 42 in × 30 in × 12 in NEMA 1 control enclosure.
• Local operator controls for recirculation fan and heater bank, plus operating status indication.
• 60A non-fused disconnect and enclosure cooling fan were included in the control package.

SAFETY ARCHITECTURE

• Applicable standards basis: NFPA 79, NFPA 86, UL 508A.
• Safety logic included recirculation airflow proving, excess-temperature shutdown, and heater shutdown when safe operating conditions were not met.
• The control package maintained fan operation until the oven cooled below 250°F.

SERVICE / INSTALLATION ARCHITECTURE

• 36 in door swing at the oven face.
• 36 in control enclosure door swing clearance.
• 6 in fan removal clearance.
• 15 in heater plug removal clearance.