Problems, Adjustments, and Troubleshooting

Uneven Temperature Uniformity

Air circulation is very important to proper oven operation. Improper air circulation could result from:

Overload Oven. Leave space between articles on each shelf to allow air to move between parts. Stagger parts from one shelf to another to prevent dead spots in the air pattern.

Cold Spots at Front of Oven. Open the exhauster and intake damper is enough to prevent fouling of the work. Where significant amounts of solvent or moisture are being driven off in the oven, it is necessary to exhaust enough air to remove this material. When the exhaust is increased, the fresh air intake must also be increased. Failure to do this will result in cold spots within the oven, particularly around the doors, since air will be drawn in past the gaskets. When the fresh air intake damper is properly adjusted it will equal out your hot and cold spots within the oven. Maximum rating is with exhaust dampers full open.

CAUTION: Do not exceed maximum permissible solvent load stated on control panel door label.

Hot or Cold Spots within Oven. Ovens are equipped with louvered ductwork. The louvers are factory adjusted for the best temperature uniformity, but may be adjusted to give the best performance for your particular process. These louvers are not designed for frequent adjustment and should be changed only when load requirements make it necessary. Louvers should be opened where the work space is cold and closed where it is hot.

Failure to Reach Set Temperature or Slow Heat-Up

BURNED OUT FUSE. In addition to any fuses in your fused disconnect switch, check all fuses located inside the control panel as shown on the wiring diagram. Depending upon the particular oven involved, it is possible for a fuse to open without affecting the pilot lights or other visible signs and still affect the heat circuit.

IMPROPER LINE VOLTAGE. Check oven nameplate voltage to assure it matches incoming voltage. Measure voltage at oven to determine if excessive line drop is causing a reduced power input. This could be caused by too many devices connected to the same circuit, or by undersized wiring between the oven and line power source.

REDUCED BLOWER SPEED. Loose or worn drive belts could prevent the recirculating fan from attaining its design speed. This results in reduced air flow and inefficient heat transfer from the heat source to the work area.

INCORRECT BLOWER ROTATION. This results in reduced air flow and inefficient heat transfer from the heat source to the work area. (See your installation instructions)

MOTOR DOES NOT RUN. The magnetic motor starter “Motor On” light will not remain on if the overload has tripped. Disconnect power to the control cabinet before opening. Then push the reset button, located on the motor overload relay. In high ambient temperature conditions, nuisance tripping may occur. Note: If high ambient temperature conditions exist, adjusting the overload to a higher setting may be needed.

DEFECTIVE OR IMPROPERLY CALIBRATED TEMPERATURE CONTROLLER. See your temperature control manufacturer’s instructions for the proper operation and adjustment.

TRIPPED OUT EXCESS TEMPERATURE CONTROLLER. On ovens so equipped, the control may require manual resetting. Depending upon the specific devices used, they may be tripped by either an excessively high oven temperature, and unusually low ambient temperature or a sensing failure. Before placing the equipment back into operation determine what caused the safety device to actuate and correct the condition.

DEFECTIVE OR IMPROPERLY CALIBRATED EXCESS TEMPERATURE CONTROL. See the excess temperature control manufacturer's instruction in your manual for the proper operations and adjustment.

CAUTION: If the oven is equipped for use with flammable solvents or vapors, the excess temperature control is factory set at the maximum temperature and must not be exceeded.

Failure to Reach Set Temperature (Gas oven)

Contact your local gas company service engineers. You will find them most eager to be of assistance in making proper adjustments. Have them check all installations as they are aware of the many variables which can affect your operations.

TRIPPED OUT FLAME SAFETY RELAY. A safe-start timer is built into the safety relay which will shut the system down if pilot ignition is not proved in approximately 10 seconds. Wait about 1 minute. Then turn burner on to try to re-ignite.

COMBUSTION AIR AND EFFECT OF NEGATIVE AIR PRESSURE IN THE BUILDING. Every burner must take in a minimum of 10 times as much air as fuel for proper combustion, therefore an adequate supply of combustion air must be assured. Many buildings in which this oven will be installed will be large enough to have enough “cracks” and leakage of air to the inside. However, many buildings now have exhaust fans, spray paint booths, cleaning booths, sand-blast booths, etc. where air is drawn out much faster than it comes in. this creates a negative pressure inside the building which is enough to overcome the natural draft created in the oven, and the oven will not work properly. The effect of the negative pressure is compounded when dock doors, walk ways, and windows are closed. This is particularly true in the winter time. In such situations, the squirrel cage fans of the oven gas burners cannot compete for air with these types of devices. Thus, the burners may become starved for air. The lower air flows to the burners may cause the following undesirable conditions:

Lower air flow causes uneven temperatures in the oven and causes the combustion temperature of the burner to rise. The hotter combustion gases emitted from the burner to heat the oven may damage the combustion chamber. Very high building negative pressures may overcome the oven natural negative pressure and draw heat, smoke, and/or odor out of the oven.

Where the building negative pressure is fairly small the oven will work just fine as shipped from the factory or the burners can be “re-tuned.” Contact Technical Support should “re-tuning” of the burners be required.

In situations where tuning the burners will not correct the problems with excess building negative pressure, outside air ducting will probably be required.

When the oven is installed close to an outside wall rigid duct may be run from the burner intakes straight through the wall. It is recommended that the duct be under ten feet long and as straight as possible.

Outside air ducting is also desirable or beneficial in work areas or installations that have unusually high amounts of dust or particle concentrations that can inhibit the blower’s ability to draw in air for proper operation, or solvent fumes that can corrode the oven. “Dirty blower wheels” are the primary maintenance problems with these ovens. Blowers should be checked and cleaned frequently, sometimes daily, even if outside air is used.

CAUTION: If the oven is installed in an area with a high negative pressure, the oven will not work properly unless outside air is ducted to the burners. Consult Tech Support if you suspect the installation location may be subject to excessive negative pressures.

In some cases, if the negative pressure in the building is extremely high, while ducting outside air to the burners will allow for proper operation of the burners and control system, at times smoke may be drawn out of the oven around the door gaskets and around the openings. In situations such as this, the oven should either be relocated to an area of the building with less negative air pressure, or make-up air must be added to the building in the area where the oven is located in order to reduce the negative pressure in this area of the building.