Heat Pump Indoor Coil Systems

The indoor coil for heat pump systems may either be a gas coil or a liquid coil.

Gas Coil Configuration

If this is a gas coil it can be used in either:

• Condenser mode for winter heating
• DX mode for cooling

Liquid Coil Options

If as a liquid coil, there are two options:

1. 2-pipe coil where sometimes heating sometimes cooling
2. 4-pipe coil that has different circuits (see liquid coils for details)

Natural Refrigerants for Gas Coils

Due to F-Gas regulations and the goal to remove all synthetic refrigerants there is a move to all natural refrigerants:

• Pentane (R601) – Hydrocarbon with excellent thermodynamic properties
• Propane (R290) – Highly efficient with low GWP
• Ammonia Ammonia (R717) – Traditional refrigerant for industrial use
• Carbon Dioxide (R744) – See Article 744 for applications
• Water Fan coils For chiller/heatpump applications
• SSFINS – Stainless steel fins for corrosive environments (longer life)

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