Troubleshooting
Table 5. Air handler troubleshooting recommendations
Symptom | Probable Cause | Recommended Action |
Short belt life | Worn sheaves | Replace sheaves. |
| Misaligned belt | Realign drive with MVP sheave set at mean pitch diameter. |
| Grease or oil on belts | Check for leaky bearings. Clean belts and sheaves. |
| Belt slipping | Improper belt tension. Adjust tension. |
| Belts rubbing | Remove obstruction or realign drive for clearance. |
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Bearing noise | Poor alignment | Loosen bearing set screws and realign (see the “Bearing Set Screw |
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| Alignment” section on page 50). |
| Failed bearing | Replace bearing. |
| Inadequate lubrication | Replace bearing. |
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Low water coil | Incorrect airflow | Check fan operating condition. |
capacity | Incorrect water flow | Inspect the water pumps and valves for proper operation and check |
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| the lines for obstructions. |
| Incorrect water temperature | Adjust the chiller or boiler to provide the proper water |
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| temperature. |
| Coil is piped incorrectly | Verify coil piping (see the “Coil Piping and Connections” section on |
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| page 28. |
| Dirty fin surface | Clean the fin surface (see the “Coils” section on page 52). |
| Incorrect glycol mixture | Verify glycol mixture and adjust if necessary. |
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Low refrigerant coil | Incorrect airflow | Check fan operating condition. |
capacity | Expansion valve is not operating properly or is | Check sensing bulb temperature. |
| sized incorrectly | Verify valve operation. |
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| Verify proper valve size. |
| Incorrect refrigerant charge | Verify refrigerant charge and adjust if necessary. |
| Condensing unit failure | Verify condensing unit operation. |
| Coil is piped incorrectly | Verify coil piping (see the “Coil Piping and Connections” section on |
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| page 28). |
| Clogged refrigerant line filter | Change filter core. |
| Failure of suction/liquid line components | Verify component operation |
| Dirty fin surface | Clean the fin surface (see the “Coils” section on page 52). |
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| Note: Do not use steam to clean refrigerant coils. |
| Fin frosting | Verify defrost cycle operation. |
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| Verify frostat operation. |
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| Verify refrigerant charge. |
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Low steam coil | Incorrect airflow | Check fan operating condition. |
capacity | Coil is piped incorrectly | Verify coil piping (see the “Coil Piping and Connections” section on |
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| page 28). |
| Incorrect steam pressure | Verify steam pressure and adjust if necessary. |
| Excessive steam superheat | Check steam superheat. |
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| Steam superheat should not exceed 50ºF. |
| Failure of steam line/condensate return | Verify component operation |
| components |
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| Boiler failure | Verify boiler operation |
| Dirty fin surface | Clean the fin surface (see the “Coils” section on page 52). |
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Drain pan is | Plugged Drain Line | Clean drain line |
overflowing | Unit not level | Level unit |
| Improper trap design | Design trap per unit installation instructions |
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Standing water in | Improper trap design | Design trap per unit installation instructions |
drain pan | Unit not level | Level unit |
| Plugged Drain Line | Clean drain line |
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Wet interior | Coil face velocity too high | Reduce fan speed |
insulation | Improper trap design | Design trap per unit installation instructions |
| Drain pan leaks/overflows | Repair leaks |
| Condensation on surfaces | Insulate surfaces |
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Excess dirt in unit | Missing filters | Replace filters |
| Filter bypass | Reduce filter bypass by ensuring all blockoffs are in place. |
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Microbial growth | Standing water in drain pan | See “Standing water in drain pan” |
(mold) inside air handler
| 57 |