Chapter 16: Troubleshooting & Maintenance in HVAC

Maintenance and troubleshooting are essential for ensuring the long-term performance, energy efficiency, and safety of HVAC systems. Whether it's a home AC unit or a large commercial chiller, knowing how to diagnose problems and maintain equipment is a key skill for HVAC professionals.

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🔹 16.1 Common HVAC Problems and Troubleshooting Techniques

✅ Window & Split AC Units

Problem	Likely Cause	Troubleshooting Tip
AC not cooling	Dirty filter, refrigerant low, faulty thermostat	Clean filter, check refrigerant level
Water leaking indoors	Clogged drain pipe	Flush the drain pipe
AC shuts off randomly	Overheating compressor, sensor issue	Check thermostat sensor, clear airflow
Foul smell	Mold in filter or ducts	Clean or replace filters
Loud noise	Loose fan, damaged motor	Tighten screws, inspect motor bearings

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✅ Chiller Systems

Problem	Likely Cause	Solution
High condensing pressure	Dirty condenser coil, air/water flow issue	Clean condenser, ensure proper flow
Low suction pressure	Refrigerant shortage, expansion valve fault	Check for leaks, inspect expansion valve
Compressor not starting	Electrical fault, pressure switch issue	Check electrical panel, reset high-pressure switch
Excessive vibration	Misalignment, worn bearings	Inspect motor alignment, service bearings

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🔹 16.2 Types of Maintenance

🔧 Preventive Maintenance (PM)

Regular, scheduled service to prevent breakdowns

Done monthly/quarterly/annually
Reduces downtime and costly repairs

Examples:

Cleaning filters and coils

Lubricating moving parts
Checking refrigerant pressure
Inspecting electrical connections

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🔧 Corrective Maintenance

Performed after a failure or performance drop

Includes replacing faulty parts, repairing leaks, etc.

Examples:

Replacing burned-out motors

Fixing refrigerant leaks
Repairing damaged compressors

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🔹 16.3 Maintenance Logbooks

A maintenance logbook records:

Entry Type	Details Logged
Service Date	When the service was done
Technician Name	Who performed the maintenance
Equipment Serviced	AC model, chiller type, etc.
Work Done	Cleaning, part replacement, checks performed
Observations	Issues found (e.g., low refrigerant, noise)
Next Due Date	Scheduled next maintenance

📝 Importance: Helps in warranty claims, auditing, predicting failures, and proving compliance with safety codes.

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🛠️ Practical: How to Service a Window AC

Steps:

1. Turn off and unplug the AC

2. Remove front panel and filters

3. Clean filters using mild soap and water

4. Use blower or vacuum to remove dust from coils

5. Check and unclog drain pipe

6. Inspect wiring and capacitor connections

7. Clean fan blades and lubricate motor if needed

8. Reassemble, plug in, and test cooling

✅ Tip: Use fin comb to straighten bent fins on the condenser/evaporator.

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📄 Assignment/Interview Questions

✅ Q1: Why is regular servicing important in HVAC?

Answer:
Regular servicing helps:

Maintain energy efficiency

Prevent unexpected breakdowns
Extend the lifespan of the system
Improve indoor air quality
Ensure safety by checking electrical and refrigerant components
Comply with manufacturer warranty terms

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✅ Q2: Common symptoms of refrigerant leakage?

Answer:

AC not cooling effectively

Ice formation on evaporator coils
Hissing or bubbling sound from the unit
Compressor running continuously
High electricity bills
Low refrigerant pressure on gauges

✅ Confirmed by pressure test and UV dye or electronic leak detector.