Mini-Split Heat Pump

Overview

A mini-split heat pump heats and cools a single room without ductwork. It splits into two boxes: a slim Indoor Unit mounted high on a wall and a Outdoor Unit sitting on the ground or a bracket outside. A thin refrigerant Refrigerant Line Set and a control wire are all that pass between them, so installation needs only a small hole through the wall. The same machine cools in summer and heats in winter by reversing the direction it moves heat, which is what makes a heat pump far more efficient than resistance heating.

The indoor head pulls room air through the Evaporator Coil with a quiet Cross-Flow Blower, steers the discharge with motorized louvers, and answers an IR Remote Control. Outside, the Inverter Rotary Compressor and Condenser Coil do the thermodynamic work, the Reversing Valve flips between heating and cooling, and the Inverter Drive Board sets the compressor speed.

How it works

Cooling and heating are the same vapor-compression cycle run in opposite directions. In cooling, the Inverter Rotary Compressor pressurizes refrigerant, the outdoor coil rejects heat, the refrigerant expands, and the indoor Evaporator Coil absorbs heat from the room. The Reversing Valve is a four-way valve that swaps the roles of the two coils on command, so in heating the outdoor coil gathers heat even from cold air and the indoor coil releases it into the room.

What sets a modern mini-split apart is the Inverter Drive Board. Instead of switching a fixed-speed compressor fully on and off, it rectifies mains power and synthesizes a variable-frequency drive for the compressor motor, using IGBT power switches under microcontroller control. The Inverter Rotary Compressor then runs slow and steady at part load and ramps up only when demand is high. This continuous modulation holds temperature within a fraction of a degree, eliminates the noisy start-stop cycling of older units, and is the main reason inverter mini-splits reach such high efficiency ratings.

Comfort and quiet come from the indoor side. The Cross-Flow Blower is a long cross-flow fan that moves a wide, gentle stream of air at low noise, and the Louver Stepper Motor steppers aim that air up or down. The unit talks to a handheld IR Remote Control, while the indoor and outdoor control boards coordinate over the interconnect wire. The whole circuit is charged with low-GWP R32 held in the outdoor unit and released into the Refrigerant Line Set when the service valves are opened at commissioning.