Frequently Asked Heater Questions

QIs ETL the same as UL?

AETL and UL are similar. Both are nationally recognized testing laboratories that test, certify and inspect products for safety and performance for manufacturers. RuppAir exhaust fans are tested to UL Standards UL 762 & UL 705. You can visit this link for a comparison.

QHow can i prevent dust and pollen from coming through the supply duct?

AYou can apply Super Filter Coat, a water soluble adhesive, to the mesh filter after each washing. The adhesive is characteristic of fly paper, as it traps the dust and dirt particles from the airstream. This is available for purchase from our sales reps. It is part number 412.

QHow does the Remote Heater Control Panel work?

AThe Manual/Off/Auto switch determines how the heat is turned on and off.

  • If this switch is in the 'Manual' position, the heat is turned on and off by the 'Heat/Vent' switch.
  • If it is in the 'Auto' position, it is turned on and off by the intake air thermostat located in the unit on the roof. When the outside temperature falls below the set point of this thermostat, the heat comes on. The heat shuts off when the outside temperature rises above the set point.
  • There are two configurations available for the remote panel, a 3-position and a 2-position. The 'Off' position turns the blower off on a 3-position panel. On a 2-position panel it only turns off the heat; the blower is controlled by another panel.

QWhy won’t the heat come on? the makeup heater blower is running.

AThere are several reasons why the heat may not be working. Be sure to:

  • Check the high limit reset. If tripped, reset.
  • Check the temperature setting on the heater 'ON' thermostat. The setting must be higher than the outside air temperature.
  • If there is a remote control panel, check the switch positions. They should be on 'Manual' and 'Heat.'
  • Make sure the air flow is within the performance range of the unit. Air flow can be reduced by clogged filters, collapsed duct, or closed outlet dampers.

QWhy won’t the fan turn on? the makeup heater has power.

AIf the unit has a damper, verify that it is opening. It must be fully open before the blower will operate. In addition, check the overload and circuit breaker in the unit and reset if tripped.

QWhy isn’t the supply fan performing as well as it did in the past?

AThe fan may have a loose or worn belt. Other possible causes are dirty or clogged filters located in the unit on the roof. Regular preventive maintenance will keep the fan operating at peak performance.

Qwhy is the fan overload tripping?

AThe overload provides protection for motors that do not have internal thermal protection. Overload protection is included on all three phase and large single phase motors. If a motor overamps or the current draw on the incoming power leads is unbalanced, the overload will trip. Overamping can result when using a motor that is not large enough or when running the fan at higher RPM's than needed. Slow the fan down if possible, but if this is not an option, replace the motor with a larger HP motor. If the motor has an unbalanced load, the motor may be defective or the power supply may be unbalanced. If one of the lines of a 3-phase power supply has lost its voltage, the motor will run on only two lines and overamp. Another common cause of overload tripping is a lightning storm or power outage. When the power comes on again, voltage is usually low because of the great demand on the power grid. As the voltage goes down, the amperage goes up and the overload trips.

QWhy is the fan motor shutting off and starting again after several minutes?

AThe motor is probably shutting off on thermal overload. The motor is overheating and restarts after it cools down and the thermal overload resets. This only happens with single phase motors that are thermally protected. The name plate will tell you if it has internal protection. To fix the problem, first measure the amp draw while the motor is running and compare it with the nameplate. If it is not much higher, you may only need to slow the fan down until it is at or below the running amps indicated on the name plate. If slowing the fan down is not an option, you will need to replace the motor with a larger HP motor. However, it could be a defective motor.

Qwhy is the fan vibrating?

ASeveral things can cause vibration. Before assuming the wheel is unbalanced, check other possible causes first. Look for any obvious signs of a rag or foreign object stuck in the wheel. If the fan was recently cleaned, make sure all of the grease was removed from the wheel (grease can cause it to be out of balance). Check for any mechanical problems involving the motor, belt, bearings, or wheel. To check the motor, remove the belt and run only the motor. If it vibrates, replace the motor. To check the belt, ensure it is in good condition. If the belt is in poor condition, replace it. Check to make sure the blower pulley and the motor pulley are in alignment. Check the bearings for wear or damage. The bearings may also need lubrication. Finally, check to make sure the fan is secured to the curb. Just adding an extra screw can sometimes quiet a noisy fan. Note that if a fan is operating outside of its performance range, it will also vibrate.

QHow do you replace a pulley?

ASingle groove pulleys are usually easy to remove after loosening the set screw. Larger pulleys that have a tapered compression bushing are removed by taking out the two hex bolts and placing them in the other two holes. When tightened, the bushing will pop out and the pulley can be removed. When replacing the pulley, make sure the taper of the pulley and the bushing match.

QHow do you adjust a pulley?

AThere is an adjustable sheave on the motor. There are two hex set screws on the pulley. One secures the pulley to the shaft. The other allows the two halves of the pulley to be adjusted closer together or further apart. Be sure when adjusting to retighten the set screws on a flat side of the pulley base. Moving the halves closer together increases the fan speed, while moving them further apart slows it down. Note that double groove pulleys must be turned the same number of turns or the belts will not sit properly in the grooves. Always be sure to check motor amperage after adjusting pulleys.

QWhy won’t the supply fan turn on?

AIf the system was provided with our control panel, the system is probably in fire condition. In this mode the exhaust fan will not shut off and the supply fan will not come on. Other possible causes may include: the R1 relay is bad in the control panel or the contactor coil is open.

QWhy does the direct fired makeup heater work fine on a mild day but blows cold air on very cold days?

AThe high fire limit is set too low. Refer to the operator's manual and readjust.