05
MIETZSCH GmbH Lufttechnik Dresden
s
www.mietzsch.de
Uneven running of the fan is often a clear indication of deposits on the impeller. Check and clean immediately.
The motors are usually equipped with permanently lubricated bearings with a service life of up to 50,000 hours,
depending on the operating conditions. Relubrication is thus unnecessary.
Replace defect antifriction bearings or renew the complete motor (see Repair instructions).
The fan must be inspected thoroughly after about 10 years. A specialist must then decide on its further use.
5. Repair instructions
Always switch off the fan before starting any work on it. Take measures to ensure that it cannot be switched on during
repair work.
After repairs, proceed as for commissioning (see Section 3.4).
5.1 Cleaning
To clean the fan, detach the hood and the entire drive assembly (impeller, motor and motor support ring) from the lower
section (see Section 5.2).
For pressure-controlled fans, carefully disconnect the pressure measuring hose from the pressure sensor before
dismantling. The bore for the pressure sensor must be clean and free of deposits.
Cleaning fluids must not damage the construction materials, particularly the plastics.
Do not use hard objects for mechanical cleaning.
5.2 Roof fans VRR/702(701) with an internal rotor motor (standard motor)
To replace the drive assembly or the motor, dismantle the fan into its main assemblies:
Dismantling
Detach the hood and the safety screen (upwards). If necessary, remove the deflector ring first.
Disconnect the electrical connections
Unfasten the connection between the motor support ring and the support column and lift off the drive assembly
(motor with motor support ring and impeller). The drive assembly is available as a spare part and can be replaced
at the site without any special tools.
Attention!
For pressure-controlled fans (DR), carefully disconnect the pressure measuring hose from the
pressure sensor before dismantling.
Remove the hub cap (caps glued or welded on must be destroyed)
Unfasten the hub fastener and pull the impeller off the motor shaft (use a puller, if necessary)
Replace the motor or repair according to the operating instructions for the motor.
Mounting
Reassemble the fan in the reverse order. Replace the destroyed hub cap as well as the lock washer of the shaft
lock.
Note:
Some of the special models are fitted with a lock that has to be opened before the safety screen can be removed.
During reassembly, make sure the screen is firmly mounted and fully functional.
5.3 Roof fans with an external rotor motor (VRR/ALM)
safety screen
hood (PUR)
A
B
motor support ring
impeller
motor
inlet nozzle lower section (PUR)
A
Isolation of structure-borne noise
(models 160, 200 and 315)
rubber
B
Vibration isolation
(models 400 and 500)
steel spring
Dismantle these fans analogously to VRR/702 (See Section 5.2). In
models with an external rotor motor, the entire drive assembly (impeller,
motor and support ring) has to be replaced. The fan may not be correctly
balanced if only the motor is replaced.
Attention!
For the special design DR (pressure-controlled), carefully
disconnect the pressure measuring hose from the pressure sensor before
dismantling.
5.4 Roof fans with an EC motor (VRR/ALM-EC)
Remove the drive assembly (impeller, motor and support ring as well as
the control unit mounted on the support ring) as described in Section 5.3.
The control unit should only be removeed or repaired after consultation
with the manufacturer.
hood (PPs)
external rotor
motor
repair switch
oi_vrr (11/09)
