Homeowner's condenser died on an older R-22 system.

This is a serious problem. You cannot mix R-22 and R-410A equipment.

Key issues:

1. Oil incompatibility: R-22 systems use mineral oil; R-410A requires POE or PVE oil. Mixing oils causes poor lubrication and compressor failure.

1. Pressure mismatch: R-410A operates at much higher pressures than R-22. The existing indoor coil and lineset aren't rated for these pressures, creating a safety hazard.

1. Contamination: Flushing cannot remove all mineral oil residue. Even small amounts will mix with the new oil, causing sludge and system failure.

1. Refrigerant migration: Different temperature glide characteristics mean the indoor coil won't evaporate R-410A properly.

Code compliance: This violates EPA Section 609 regulations and manufacturer specifications. Most jurisdictions require complete system replacement when changing refrigerant types.

Recommendation: Insist the contractor replace the entire system - both indoor coil and outdoor unit - with matching R-410A components. The existing copper lineset may be reusable if properly evacuated and it's the correct size, but the indoor coil must be replaced.

If they refuse, get a second opinion. This installation will likely fail within months and void all warranties.

This is a code violation and will fail prematurely. Do not proceed.

1. Refrigerant Incompatibility (IMC 1101.2 / Manufacturer Specs) R-410A operates at ~50% higher pressure than R-22. The existing indoor coil (evaporator) and metering device (TXV/piston) are rated for R-22 pressures. They will leak or burst. You cannot mix refrigerants.

2. Oil Contamination (AHRI Guideline K / Manufacturer Specs) R-22 uses mineral oil; R-410A uses POE oil. Flushing removes loose debris, but cannot remove mineral oil soaked into the copper walls and coil pores. Residual mineral oil forms acidic sludge with POE oil, destroying the new compressor. Manufacturers void warranties on flushed R-22 linesets/coils.

3. Metering Device Mismatch The existing TXV or piston is calibrated for R-22. It will not control superheat correctly with R-410A, causing floodback or starvation.

4. Code Compliance

• IMC 1101.2: Equipment must be installed per listing/manufacturer instructions. No OEM approves this retrofit.
• IMC 1107.2: Piping must be compatible with the refrigerant.

The Only Correct Fix: Replace the entire system: Condenser, indoor coil (cased, R-410A rated), lineset, and TXV. If the furnace/air handler is compatible, a cased coil swap is standard.

Exception (Rare): Only if the existing coil is factory-rated for dual refrigerant (R-22/R-410A) and the lineset is replaced. This almost never exists in "older" systems.

Action: Tell the contractor to quote a full system changeout (condenser + cased coil + lineset) or hire a different company. Installing a 410A condenser on an R-22 coil is negligent.