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MUA-SVX006B-EN
Problem Probable
Cause
Solution
Blower Wheel
1. Loose on shaft
2. Defective blower wheel. Do not run blower.
Contact manufacturer.
3. Unbalanced.
4. Worn as a result of contact with abrasive or
corrosive material.
Housing
1. Foreign material in housing.
2. Cutoff of other part loose (rattling during
operation).
Electrical
1. Lead-in cable not secure.
2. AC hum in motor or relay
3. Starting relay chatter.
4. Noisy motor bearings.
5. Single phasing a 3–phase motor.
Shaft
1. Bent.
2. Undersized. May cause noise at blower
wheel, bearings or pulley.
3. If more than two bearings are on a shaft,
they must be properly aligned.
High Air Velocity
1. Duct work too small for application.
2. Blower selection too small for application.
3. Registers or grilles too small for application.
4. Cooling coil with insufcient face area for
application.
Obstruction in High
Velocity Air Stream
may cause Rattle
or Pure Tone
Whistle
1. Dampers.
2. Registers.
3. Grilles.
4. Sharp elbows.
5. Sudden expansion in duct work.
6. Sudden contraction in duct work.
7. Turning vanes.
Pulsation or Surge
1. Blower too large for application.
2. Ducts vibrate at same frequency as blower
pulsations.
Rattles and/or
Rumbles
1. Vibrating duct work.
2. Vibrating cabinet parts.
3. Vibrating parts not isolated from building.
CFM Low -
Insufcient Air
Flow
Blower
1. Forward curved blower wheel installed
backwards.
2. Blower operating backwards.
3. Cutoff missing or improperly installed.
4. Blower wheel RPM too low.
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