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Frequently Asked Fan Questions

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.

QCan I order a fan without a motor?

AYes, most fan models can be ordered this way. This is called a fan shell. It is a complete fan less the drive package. The drive package inlcudes the motor, pulley, and belts.

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.

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.

QWhy is the fan leaking when it rains?

AFirst, determine whether the water is leaking inside or outside of the duct. If the water is inside the exhaust plenum (the area behind the filters), the grease drain on the fan may be clogged and the water may be overflowing the venturi on the lower baffle assembly. The silicon seal between the baffle assembly and the fan base could also be the cause of the leak. If the water is leaking outside of the duct and is dripping on the outside of the plenum or collecting in the light fixtures, the fan curb was likely not flashed to the roof properly.

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 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 exhaust fan not 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 or the fan wheel may be loaded with grease. Regular preventive maintenance will keep the fan operating at peak performance.

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 won’t the exhaust fan shut off when i turn the switch off?

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, the fan switch is defective, or the contactor is stuck in the closed position.

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.

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.

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.

QWhy is the motor on my direct drive fan running at higher amps than the nameplate lists?

AOn direct drive motors, the FLA listed on the nameplate is the amperage at its highest speed. The speed control reduces the speed of the motor by lowering the voltage supplied. Basic electric laws dictate that when you decrease the voltage, the amperage increases. This is normal for these types of motors. Speed controls used on direct drive fans are rated higher than the motor to accommodate for this increase.

QIs there a comparison of fan noise to noises we recognize?

AYes. View the comparison.

QHow do you change the voltage of a fan in the field?

AAll motors are suitable for high and low voltage applications. Single phase motors are rated 115/208-230. This means the low voltage is 115 volts and the high is 208-230 volts. Similarly, three phase motors are rated 208-230/460. This means that the low voltage is 208-230 volts and the high voltage is 460 volts.

To change the supply voltage, refer to the diagram on the motor label for wiring instructions. If a prewire is included on the job, you will need to replace the contactors and/or overloads because of the change in FLA (refer to the motor label). If the supply fan is a heater, you will need to rewire the KVA transformer for the new voltage. NOTE: A single phase motor cannot be converted to three phase and a three phase motor cannot be converted to single phase. The motor must be replaced.

QDoes adding an explosion proof motor to a fan make it explosion proof?

ASimply adding an explosion proof motor to a fan does not make it explosion proof. Explosion proof fans must be modified to meet the AMCA requirements listed below. In some jurisdictions, explosion proof switches and filled conduits must be provided.

The term "Explosion Proof Exhaust Fans" must be quantified as to its true definition. There is no such thing as "Explosion Proof" in exhaust fans, blowers or motors. Fans can be manufactured to be "Spark and/or Explosion Resistant". The Air Movement and Conditioning Association (AMCA) has three classifications for "spark resistant" fans and blowers. These are defined as AMCA Types A, B or C spark resistant construction. Type A construction requires that all materials of the fan or blower that are "in contact with the air stream" be made of spark resistant nonferrous material such as aluminum or brass. Type B construction requires a nonferrous wheel and a rubbing ring around the hole where the fan or motor shaft enters the fan or blower housing. Type C construction requires a nonferrous plate on both sides of the inside of the fan or blower housing. The type of construction you require is dependent on the ambient location and/or application severity to which your fan will be subjected. You need to be very careful in selecting which type of spark resistant construction you require and specify. If you are not knowledgeable in this area, you should hire a consultant who is.

Explosion proof motors are not guaranteed to be explosion proof either. They are designed so that "if there is an explosion within the motor, the motor design will contain the explosion within the motor and not allow it to go to atmosphere". Explosion proof motors are designed or rated by Classes, Groups and "T" Codes for the atmospheres in which they will be operating. If an explosion proof motor is improperly selected for the actual ambient atmosphere it is operating in, it can cause an explosion. Again, if you are not knowledgeable in specifying what type of explosion proof motor you require for your application, rely on someone that is trained in this area.