Compressor grounded out on a 3-ton R-410A heat pump.

The tech likely missed acid testing and system flushing.

When a compressor "grounds out" (internal short to shell), it typically indicates severe overheating that creates acidic burn-out. This acid forms in the oil and spreads throughout the entire refrigeration system—including the condenser and evaporator coils—not just the compressor.

What was missed:

1. Acid testing - Should have tested the oil for acidity (using acid test kits) before installing the new compressor
2. System flushing - The entire system needs flushing with a compatible solvent to remove acid and carbon deposits
3. Suction line filter/drier - Often overlooked on heat pumps; should be installed in the suction line to catch debris
4. Nitrogen purge - During brazing, nitrogen should be flowing to prevent oxidation and contamination

Code reference: ACCA AQC-1 and ASHRAE Standard 15-2019 require proper service procedures including system cleanup after compressor failure.

The fix: Recover all refrigerant, completely flush the system (condenser, evaporator, lines), replace all filter/driers, install a new compressor, and use proper nitrogen purging during reassembly.

This is why the new compressor failed identically—the acid and debris from the original failure were never removed.

He missed acid and moisture contamination from the original burnout. A standard liquid-line drier cannot clean up a system after a compressor ground-out (burnout).

What he should have done (per AHRI Guideline K & manufacturer specs):

1. Install a suction-line filter-drier (SLFD) sized for the system capacity (typically 1/2" or 5/8" ODF) immediately downstream of the compressor to catch residual acid, metal shavings, and sludge circulating in the suction line and evaporator.
2. Run the system (heat/cool) for 24–48 hours.
3. Check pressure drop across the SLFD. If > 2–3 psi, or if an acid test kit (e.g., Sporlan TA-1) shows acid, replace the SLFD and liquid-line drier (LLD).
4. Repeat until pressure drop is minimal and acid test is negative.
5. Remove the SLFD (or leave it if designed as permanent) and install a fresh LLD. Pull a deep vacuum (≤ 500 microns, decay test) and recharge.

Why the second compressor failed: The burnout byproducts (hydrofluoric/hydrochloric acid, carbon, copper plating) circulated, ate the new compressor’s windings, and caused the identical ground fault.

Also verify:

• Crankcase heater wired/functioning (prevents refrigerant migration/oil dilution on startup).
• Contactor not pitted/welded (prevents single-phasing/chatter).
• Voltage imbalance < 2% (NEC 430.30, manufacturer spec).
• Superheat/subcooling correct after final charge (prevents floodback/slugging).

Bottom line: No SLFD cleanup = guaranteed repeat failure on burnout replacement.