The Thermo Scientific Precision Compact Gravity Convection Ovens, including models PR305225G (658), PR305220G (652), and PR305220GCN (669), are designed for a variety of laboratory applications requiring reliable and cost-effective heating. These ovens are suitable for use in hospitals, industry, and school laboratories for tasks such as drying, sterilization, baking, and evaporation. Specific applications include drying glassware, drying and/or baking non-flammable crystalline chemicals, pre-heating crucibles or other containers, and drying filter paper strips or rounds.
Function Description:
These ovens operate using gravity convection, meaning heat is distributed naturally within the chamber without the aid of a fan. The temperature is controlled by a bimetallic thermostat located on the front control panel, offering a temperature range from ambient +5°C to 210°C. A sheathed heater provides the necessary heat, and a pre-set high-limit bimetallic thermostat is a standard safety feature on all models. A pilot light on the control panel indicates the oven's operational status. The chamber's design incorporates one-inch thick insulation made of semi-refractory fibers, sandwiched between double walls, to efficiently retain heat. The interior walls are constructed from aluminum, and the shelves are made of steel wire, as is the surface covering the heater area, all contributing to efficient heat distribution.
Important Technical Specifications:
- Models Covered: PR305225G (658), PR305220G (652), PR305220GCN (669)
- Size: All models have a chamber volume of 1.7 cu ft (48.2 liters).
- Voltage:
- PR305225G (658): 120V
- PR305220G (652): 240V
- PR305220GCN (669): 240V
- Power Requirements:
- PR305225G: 120 Volts, 50/60 Hz, 6.7 Amps, 800 Watts
- PR305220G, PR305220GCN: 240 Volts, 50/60 Hz, 3.3 Amps, 800 Watts
- Overall Dimensions: 18½"W x 13½"D x 22½"H (47 x 34 x 57 cm)
- Chamber Dimensions: 16"W x 11½"D x 16-1/8"H (41 x 29 x 41 cm)
- Shipping Weight: 57 lbs. (26 kg) for all models.
- Performance Characteristics:
- Temperature Range: Ambient +5°C to 210°C for all models.
- Uniformity at 100°C: ±5.0°C
- Control at 100°C: ±9.0°C
- Environmental Operating Conditions:
- Pollution Degree: 2
- Installation Category: II
- Altitude: 2000 Meters MSL (Mean Sea Level)
- Humidity: 80% maximum, non-condensing
- Electrical Supply: 120VAC or 240VAC
- Voltage Tolerance: ±10% of normal rated line
- Temperature: 15°C to 40°C
- Product Usage: Intended for indoor use only.
- Construction: Durable powder-coated cold rolled steel exterior. Nickel-plated steel shelves to inhibit rust.
Usage Features:
- Simple Operation: The oven features a straightforward control panel with a power switch and a control thermostat. The control dial for the thermostat is graduated from 0 to 10 for reference purposes only, emphasizing the use of a user-supplied thermometer for accurate temperature readings.
- Temperature Monitoring: Users are advised to use an immersion thermometer (user-furnished) inserted through a grommet and into a holder on top of the oven. The immersion depth should be adjusted to 6-7/8” (175mm) from the bulb to the top of the rubber washer.
- Safety Precautions:
- The unit is not explosion-proof and should not be used with flammable or combustible materials, or in the presence of explosive gases, to prevent fire or explosion.
- Pressurized or sealed containers should not be used in the oven.
- Substances that emit toxic fumes when heated should not be processed above temperatures that cause such emissions.
- The heater is located at the bottom of the unit, and surface temperatures on the bottom cover may exceed the set point temperature. Items, especially plastic containers, should not be placed directly on the heater cover to prevent melting or burning.
- To avoid electrical short or shock, no metal objects should protrude into the space beneath the shelf/heater shield, and the oven should not be operated with the shield removed.
- The exterior surfaces, particularly the thermometer vent ring, can become hot at higher temperatures, requiring caution to avoid burns.
- Installation: Requires a properly grounded electrical outlet of correct voltage and current handling capacity. The unit should be placed in an area free of drafts and strong vibrations, away from combustible surfaces or materials.
Maintenance Features:
- Low Maintenance Design: The ovens are built for rugged performance and long life, requiring minimal maintenance.
- Cleaning: Ordinary cleaning with mild soap and water is sufficient. Spills should be cleaned promptly to prevent materials from baking onto surfaces. Abrasive cleaners should be avoided to protect the interior finish and shelves.
- Heater Access: The bottom shelf covering the heater can be removed for easy access to the heater area for cleaning or inspection.
- Troubleshooting: If the oven fails to heat, potential causes include lack of electrical power, a burned-out heater, or a malfunctioning thermostat.
- Professional Service: Internal adjustments and maintenance must be performed by qualified service personnel. Users are advised to disconnect the unit from the power source before any maintenance or servicing. For repairs or replacement parts, users should contact their Thermo Scientific dealer or Technical Services Department. No warranty repairs should be attempted without prior consultation. A Return Materials Authorization (RMA) number is required for returning any materials to the factory.
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