How a Heat Pump Reversing Valve Works

Summary

This video provides a comprehensive overview of how a reversing valve functions in a heat pump system. It explains the process of redirecting refrigerant flow between the indoor and outdoor coils, switching between heating and cooling modes. The reversing valve is controlled by a 24-volt solenoid that activates a small pilot valve, allowing refrigerant to flow in the desired direction. The video also covers key components, including the suction and discharge lines, metering devices, and the pressure differential that drives the valve. The explanation concludes with insights into brand-specific strategies for energizing the valve in different modes.

Takeaways

• 😀 A heat pump system is essentially an air conditioner with a reversing valve (also called a four-way valve) that allows it to switch between heating and cooling modes.
• 😀 The reversing valve redirects refrigerant flow between the indoor and outdoor coils, changing the roles of the coils from evaporator to condenser and vice versa.
• 😀 In heating mode, the indoor coil acts as the condenser coil, and the outdoor coil becomes the evaporator coil.
• 😀 Most heat pumps have two separate metering devices—one for cooling mode (indoor coil) and one for heating mode (outdoor coil).
• 😀 The reversing valve operates via an electromagnetic solenoid and a pilot valve, not directly by the electromagnet. The pilot valve uses compressor pressure to shift the main valve.
• 😀 The shifting of the valve in the reversing valve requires a pressure differential, which is created by the compressor’s operation.
• 😀 The electromagnet inside the reversing valve is energized in cooling mode to shift refrigerant flow towards the outdoor coil, with the suction gas directed from the indoor coil.
• 😀 Some brands (like Rheem and Ruud) energize the reversing valve in heating mode using a different strategy (like a blue wire or B terminal), rather than the orange wire used in most systems.
• 😀 The reversing valve does not shift if the system is off or when the pressures are equalized because the compressor is not generating enough pressure to create a differential.
• 😀 The purpose of the reversing valve is to change the flow direction of the refrigerant, allowing the system to either heat or cool the space by manipulating the flow through the indoor and outdoor coils.

Q & A

What is a heat pump system?

A heat pump system is essentially an air conditioner with a reversing valve, which allows it to switch the direction of the refrigerant flow, enabling it to provide both cooling and heating functions.

What role does the reversing valve play in a heat pump system?

The reversing valve redirects the flow of refrigerant between the indoor and outdoor coils, allowing the system to switch between cooling and heating modes.

How does the reversing valve work in cooling mode?

In cooling mode, the reversing valve directs the refrigerant flow to the outdoor coil, turning it into the condenser coil. The indoor coil then functions as the evaporator coil.

How does the reversing valve work in heating mode?

In heating mode, the reversing valve redirects the refrigerant so that the indoor coil becomes the condenser coil, rejecting heat indoors, while the outdoor coil becomes the evaporator coil, absorbing heat from outside.

What is the significance of the two metering devices in a heat pump system?

A heat pump system typically has two separate metering devices: one inside for cooling mode and one outside for heating mode. The outdoor metering device is used when the outdoor coil is the evaporator in heating mode, while the indoor metering device is used for cooling.

What is the purpose of the solenoid coil in the reversing valve?

The solenoid coil energizes the pilot valve, which creates a pressure differential that shifts the main valve, redirecting the refrigerant flow to either the heating or cooling mode.

What is the 'canoe' inside the reversing valve, and what is its function?

The 'canoe' is a slider inside the reversing valve that helps to redirect the refrigerant flow. It moves back and forth when activated by the electromagnetic solenoid, allowing the valve to shift between cooling and heating modes.

Why won't the reversing valve shift when the system is off?

The reversing valve requires a pressure differential between the discharge and suction lines to shift. If the system is off and the pressures are equalized, the valve will not shift.

What is the role of the pilot valve in the reversing valve operation?

The pilot valve acts like a small reversing valve inside the main valve. It is controlled by the solenoid and helps redirect the refrigerant flow by creating a pressure differential that forces the main valve to shift.

How does the compressor affect the operation of the reversing valve?

The compressor generates the pressure differential needed for the reversing valve to shift. Without the compressor creating the right pressure, the valve will not operate, as it relies on the pressure from the discharge and suction lines to move.