THERMO SCIENTIFIC PR205220MCN (01) PDF Document

The alert signals on your THERMO SCIENTIFIC PR205220MCN oven indicate important safety information:

Warning: This signal, represented by an exclamation mark in a triangle, alerts you to a possibility of personal injury.

Caution: This signal, represented by a hand in a stop sign shape, alerts you to a possibility of damage to the equipment.

Note: This signal, represented by a document icon, alerts you to pertinent facts and conditions.

Hot Surface: This signal, represented by three wavy lines in a triangle, alerts you to a possibility of personal injury if you come in contact with a surface during use or for a period of time after use.

Environmental Operating Conditions

Follow these steps for unpacking and installing your THERMO SCIENTIFIC PR205220MCN oven:

Shipping Carton Inspection:

Inspect the shipping carton upon delivery for any damage. If damage is discovered, the delivering carrier should specify and sign for the damage on your copy of the delivery receipt. After unpacking, if damage is found, report it to the carrier immediately and request a damage inspection. Failure to request an inspection within a few days absolves the carrier from liability.

Location:

The oven should be located in an area free from drafts and sources of heat. Allow for natural air movement to dissipate heat from the oven. Warning: Do not place the oven on or near any combustible surface to avoid the risk of fire, property loss, injury, or death.

Leveling:

Place the oven on a level surface to facilitate the movement of materials in and out of the chamber.

Shelving:

Slide the shelves into place inside the oven and position them according to the height required for the items being heated. Caution: The bottom shelf is fixed in place to guard against access to the heater area. Do not remove the bottom shelf unless performing maintenance or repair.

Important Cautions:

Do not remove the rubber space feet. Their removal will prevent proper air venting for cooling the electronics, which can cause excessive heat buildup and erratic temperature control.

The unit must be connected to a power source that meets the electrical requirements specified on the unit’s nameplate.

The 120V unit comes with a 3-wire line cord with a molded plug and should be connected to a 120V outlet designed for 3-prong plugs. If you have an ungrounded 2-prong outlet, it is best to have a qualified electrician replace it with a new, grounded outlet.

If a plug must be installed, use only the 3-prong grounded type, rated for the unit’s load requirements and matching the power outlet. Ensure the green ground wire is secured to the plug’s ground terminal.

Any changes to electrical outlets or wiring should be done by a qualified or journeyman electrician to match the load requirements on the nameplate. It is recommended to leave the unit disconnected when not in use.

The control panel of your THERMO SCIENTIFIC PR205220MCN has the following components:

1. POWER SWITCH: Turns the unit on (green status lamp lights) and off. Part #SWX143 or #440-292-00*.

2. HI-LIMIT STATUS LAMP: This red lamp lights when the hi-limit thermostat is activated. It goes out when the oven reverts to a safe operating range. Part #360-234-00 (LAMP, RED), #360-233-01 (LAMP BASE)*.

3. CALIBRATION POTENTIOMETER (OFST): Using a jeweler’s screwdriver, the temperature readout can be adjusted for calibration.

4. LED DISPLAY: Displays the current chamber temperature.

5. TEMPERATURE CONTROL (THERMOSTAT): A knob that raises and lowers the temperature setting.

6. HEATERS STATUS LAMP: This amber lamp lights when the heaters are energized. Part #360-235-00 (LAMP, AMBER), #360-233-01 (LAMP BASE)*.

*As listed on the replacement parts list.

Follow these steps to set the temperature on your THERMO SCIENTIFIC PR205220MCN oven:

1. With the temperature control thermostat (5) in the extreme counterclockwise position, turn the power rocker switch (1) to the ON position. The switch’s green status lamp will light up.

2. Turn the temperature control thermostat (5) clockwise to increase the temperature and counterclockwise to lower it. The amber status lamp (6) above the thermostat will turn on when the heaters are energized.

3. Wait for the chamber temperature to stabilize before advancing the thermostat too rapidly to reach the target temperature. Note that the dial setting for a specific temperature is an approximation and can be affected by factors like line voltage changes, ambient conditions, and the materials being heated.

4. Read the LED display (4) to monitor the chamber temperature. As you gain experience, you will get better results in setting specific target temperatures.

5. Always allow time for the oven to reach the target temperature and stabilize before making further adjustments.

A factory-set hi-limit thermostat cuts off power to the heater if the maximum operating range is exceeded. The red status lamp (2) on the control panel indicates when the hi-limit thermostat is controlling. It goes out when the oven returns to a safe operating range.

Caution: At higher temperatures, the exterior of the oven, particularly the vent ring on top, becomes warm to the touch. To avoid burns, do not touch these surfaces.

For general cleaning of your THERMO SCIENTIFIC PR205220MCN oven, follow these guidelines:

Warning: Disconnect the plug from the electrical outlet before attempting any maintenance or repair of this unit.

The bottom shelf covering the heater can be removed for easy access to the heater area.

Clean up any spills as soon as possible to prevent materials from baking onto surfaces. When the oven is cool, use mild soap and water to clean surfaces. Rinse thoroughly and dry. It is best to avoid highly abrasive cleaners, which can damage the finish of the interior surfaces and shelves.

Stainless steel requires proper care to prevent rust and corrosion. Maintaining a neutral pH and performing frequent cleanings with detergent and water will ensure years of service.

Water Guidelines:

Distilled water is recommended. If the water is very pure, it may be corrosive; add 2 to 40 PPM of disodium phosphate or sodium bicarbonate to achieve a pH of 7 to 9. If unavailable, clean, aerated soft tap water with a total solids concentration of < 500 PPM can be used. It is not recommended to use 18 MEG OHM deionized water; if this is the only source, mix it with regular tap water at a 50/50 ratio.

The pH Factor:

Check pH regularly. If pH is <6.0, add disodium phosphate to increase it to a 7 to 9 value. If pH is >10.0, add sodium bisulfate to decrease it. Avoid harsh alkalines or acids, which can cause localized corrosion and unstable pH.

Cleaning Methods:

Do not use metallic pads. For stubborn stains, use a plastic light-duty cleansing pad and rub gently in the direction of the metal grain. If stains persist, use one of the following:

• “Scale removers” from local supermarkets or hardware stores.

• A 15% to 35% phosphoric acid solution from a laboratory supply distributor.

• Citric acid-based cleaners.

• Bathroom tub and tile cleaners.

Always follow the manufacturer’s directions for any cleaning product and finish by rinsing with clean water and air drying.

Caution: When handling cleaning chemicals, always work in an area with adequate ventilation and use precautions outlined in the Material Safety Data Sheet (MSDS).

Yes, some chemicals should be avoided or have limited exposure time on the stainless steel surfaces of your THERMO SCIENTIFIC PR205220MCN oven.

Never use the following on stainless steel:

• Aqua regia

• Ferric chloride

• Iodine

• Sodium acid

• Sodium azide

Limit exposure to a maximum of 3 hours for the following chemicals and always clean surfaces immediately after use:

• Aluminum chloride

• Barium chloride

• Calcium chloride

• Chlorinated Lime

• Citric acid (boiling)

• Dakin’s solution

• E.D.T.A.

• Ferrous chloride

• Lysol

• Mercury salts

• Phenol

• Potassium permanganate

• Potassium thiocyanate

• Sodium hypochlorite

• Stannous chloride

• Tartaric acid

Chemical spills, especially of the agents listed, should be removed as soon as possible. Clean the stainless steel surface with mild soapy water followed by a clean water rinse.

If your THERMO SCIENTIFIC PR205220MCN oven fails to heat, there are several possible causes:

• The oven is not receiving electrical power.

• The heater is burned out.

• The thermostat is malfunctioning.

It is recommended to have a qualified electrical technician determine the cause of the problem and make the necessary repairs.

Part replacement procedures should only be performed by authorized personnel. First, unplug the unit from the power source and ensure all surfaces are safe to touch.

1. Lay the unit on its side with the door latch facing down.

2. Remove the back panel by unscrewing the Phillips screws. Save the screws.

3. Carefully remove the insulation, noting its position for reinstallation.

4. Remove the bottom panel by unscrewing Phillips screws. Save them.

5. Remove the control knob by unscrewing the 2 Allen-head screws. Save them.

6. Disconnect the wires from the thermostat. Note the position of the wires for correct reattachment.

7. Knob removal allows access to 2 screws that mount the thermostat to the panel. Remove these screws and save them.

8. Remove the bottom shelf inside the chamber. Loosen the screw on the clamp holding the thermostat-sensing bulb to the heater. Note the bulb’s position so the new one can be clamped in the same location.

9. Slide the bulb toward the exit hole at the back of the unit.

10. Move to the back of the unit and pull the temperature sensing bulb and tube through the hole.

11. Next, pull the bulb and tube through the bottom hole. The thermostat assembly can now be removed.

12. Reverse the above procedure to install the new thermostat. Avoid making sharp bends in the temperature sensing tube, as this will impede the flow of sensing fluid.

This procedure should only be performed by authorized personnel. Unplug the unit and ensure it is cool before starting.

1. Place the unit on its side and remove the bottom plate, saving the screws.

2. Disconnect the wires from the switch. Note the sequence of pin numbers on the side of the switch and the wire attachments. The replacement switch must be oriented in the same manner with wires attached in the same sequence.

3. Compress the holding tabs on the switch and push it out.

4. Insert the new switch from the front, following the same orientation of pin numbers as the switch that was just removed.

5. Attach the wires in the same sequence as they were originally. You can refer to the wiring schematic to verify the correct sequence.

6. Reverse the remainder of the procedure to reassemble.

This procedure should only be performed by authorized personnel. Unplug the unit and ensure it is cool before starting.

1. With the unit on its side, remove the bottom plate and save the screws.

2. Note the plastic lamp unit that houses the bulb. Be alert that the lens will pop out in the next step.

3. Grasp the lamp unit and pull it a fraction of an inch toward the attached wires. The lens will pop out from the front. Save the lens.

4. Cut the wires and remove the lamp unit. Discard it.

5. To install the new pilot lamp unit, splice the two wires of the new assembly to the previously cut wires using insulated crimp connectors.

6. Re-install the lens.

7. Re-install the bottom plate.

This procedure should only be performed by authorized personnel. Unplug the unit and ensure it is cool before starting.

1. Remove the back panel and carefully remove the insulation for subsequent reinstallation. Save the screws.

2. The hi-limit thermostat is mounted on the back of the inner chamber wall.

3. Unscrew the 2 screws and nuts holding the wires. Save them.

4. Remove the screw securing the thermostat to the back of the inside wall.

5. Reverse the preceding procedure to install a new hi-limit thermostat.

This procedure should only be performed by authorized personnel. The heater is located in the bottom of the chamber. Be sure the unit has been turned off for a period of time so there is no residual heat.

1. Remove the back panel by unscrewing the Phillips screws and save them.

2. Carefully remove the insulation and save it. Note how it is positioned so it can be easily reinstalled.

3. Remove the two retaining clips that mount the heater to the back of the inside wall. Save them.

4. Remove the wires to the heater by uncoupling the quick-disconnects.

5. Remove the bottom shelf inside the chamber. Loosen the screw on the clamp which holds the thermostat sensing bulb to the heater. Note the position of the temperature sensing bulb so that the new one can be clamped in the same location.

6. Install the new heater and reverse the preceding steps to reassemble.

This procedure should only be performed by authorized personnel. First, disconnect the power cord.

1. Remove the shelves. Note that the bottom shelf is retained by a clip at the back of the oven. Lift the shelf at the front edge until the back edge can be withdrawn from the clip.

2. Remove the Phillips screws holding the shield that covers the blower wheel.

3. Inspect the blower wheel assembly for tightness and any off-center operation. Inspect the wheel itself for damage to vanes or other deterioration.

4. If the assembly is loose, tighten the setscrew holding the wheel to the motor shaft until the wheel turns true. If the wheel is damaged, replace it.

5. Replace the shield and shelves.

This procedure should only be performed by authorized personnel.

1. Disconnect the unit from the power source. If previously in use, let the unit cool down.

2. Lay the unit on its side. Remove the shelves, including the bottom one.

3. Remove the bottom cover, fan shield, and blower fan.

4. Accessing the unit from the bottom, remove the motor and bracket assembly. Disconnect the wires.

5. Remove the shaft extension, bottom fan, and motor bracket from the old motor and reinstall them on the new replacement motor.

6. Re-install the new motor assembly into the unit in the reverse order of removal.

7. Reconnect the wires.

8. Re-install the shelves. Make sure that the bottom shelf is securely in place to prevent access to the heater area.

The temperature readout calibration potentiometer (3) is located in the upper left-hand corner of the LED display, indicated by the word “OFST.” You will need a jeweler’s screwdriver, a digital thermometer, and a known reliable thermocouple (Type-K or -T).

1. Insert the thermocouple sensor through the outside top vent hole and position it in the center of the oven chamber.

2. Set the oven temperature to a desired setpoint and turn on the power.

3. Allow the temperature to stabilize for at least 2 hours before making any adjustments.

4. Compare the chamber temperature on the digital thermometer to the temperature on the oven’s readout.

5. Insert the jeweler’s screwdriver into the calibration hole (OFST) and adjust the oven readout to match the thermometer reading. Turn the potentiometer clockwise to increase the reading and counterclockwise to decrease it.

6. Take two additional readings within an approximate 30-minute time span and make any necessary adjustments to the potentiometer. This accounts for temperature variations within the oven and the time delay in sensor response.