Danfoss ICFD Defrost Module: Supplemental Application Guidelines

Introduction

This supplemental application guide outlines the specific requirements to consider when designing the liquid drain line in conjunction with the ICFD defrost module.

Liquid Drain

The liquid drain method is recognized as the most energy-efficient approach. This method ensures that only liquid condensate is returned to the suction accumulator, thereby minimizing the consumption of hot gas.

ICFD Liquid Drain Module (ICFD 20 / ICFD 20-C)

The ICFD is a float-operated valve module that opens for liquid flow when the internal liquid level lifts the float. It is a balanced type of float valve, suitable for high differential pressure applications and is available in two distinct versions:

ICFD 20 (Ammonia)

Specifically designed for ammonia, this version features a very low-weight float to accommodate low-density fluids.

Note: If the refrigeration system incorporates the ICFD 20 module, the system's test pressure should not exceed 28 bar/406 psig, unless the ICFD float ball is dismounted during the pressure test.

ICFD 20-C (CO₂)

Designed for CO₂ applications, this version has a higher weight due to a thicker wall construction, enabling it to handle high pressures.

Note: If the refrigeration system includes the ICFD 20-C module, the system's test pressure should not exceed 52 bar/754 psig, unless the ICFD 20C float ball is dismounted during the pressure test.

The ICFD liquid drain module is patent pending.

ICF Liquid Drain Method

A common configuration utilizing "Liquid drain" incorporates a solenoid valve function and a liquid drain function. This is illustrated in Figure 1.

Figure 1: Liquid drain "standard configuration"

Diagram Description: A schematic shows a refrigeration system with an evaporator, a fan, and various valves. Key components labeled are A (ICFD drain module) and B (ICFE solenoid valve module). Lines indicate refrigerant flow: Wet return line, Liquid feed line, and Hot gas line.

• A: ICFD (drain module) is the primary function for Liquid drain.
• B: ICFE (solenoid valve module) ensures the drain line is closed during freezing to prevent liquid bypassing the evaporator.

ICF Valve Station with ICFC 20P1 Loaded Check Valve

The ICFC 20P1 is designed to work with the ICFD drain module in a pump circulating system, facilitating a defrost solution without a solenoid valve in the drain line. Its function is to prevent liquid refrigerant flow through the ICFD drain module when the evaporator is in freezing mode, while providing high flow capacity during defrost mode. The ICFC 20P1 valve opens at a pressure differential of 0.5 bar and reaches full capacity at 0.7 bar, effectively replacing a traditional solenoid valve without capacity reduction.

Note: ICFC 20P1 loaded check valve is patent pending.

Figure 2: "Loaded check valve" - working principle

Diagram Description: A cross-section of a valve shows pressure inputs (P1, P2) and a valve opening characteristic curve plotted against pressure differential (Δp). The curve shows that the valve begins to open at 0.5 bar and is fully open at 0.7 bar.

It is crucial to validate that the total pressure drop across the evaporator and connecting pipes is less than 0.5 bar (73 psi) during freezing mode.

Figure 3: Liquid drain configuration with "loaded check valve"

Diagram Description: A detailed schematic of a defrost system using the ICFD and ICFC 20P1. It illustrates pressure drops (ΔP1, ΔP2, ΔP3) in different parts of the system, including the liquid supply line, evaporator, and wet return line. The total pressure drop (ΔP1 + ΔP2 + ΔP3) must be ≤ 0.5 bar (73 psi). Labels indicate components like ICFD (drain module), ICFC 20-P1 ("Loaded Check Valve"), and solenoid valves (O for operation, S for service).

• A: ICFD (drain module) is the main function of the Liquid drain.
• B: ICFC 20-P1 ("Loaded Check Valve") prevents liquid flow in the drain line during freezing and provides high capacity during defrosting.
• ΔP1: Pressure drop in the liquid supply line, including liquid head pressure.
• ΔP2: Pressure drop across the evaporator (approx. 0.2 bar/29 psi, potentially higher for evaporators with distribution nozzles).
• ΔP3: Pressure drop in the wet return line, including liquid head pressure.

Note: The ICFC 20P1 loaded check valve is not suitable for systems requiring more than 0.5 bar differential pressure. It is also not recommended for defrost systems draining to a higher pressure than suction pressure (e.g., low-temperature systems draining to intermediate temperature in 4-pipe systems). In such cases, a standard ICFC 20 check valve is recommended.

Liquid Drain to a Separate Defrost Line

This configuration involves draining condensate to a separate drain system, typically at an intermediate pressure, often referred to as a 4-pipe system. This method can slightly improve system efficiency by draining condensate to a higher pressure level.

Figure 4: Defrost system with separate drain line (4-pipe system)

Diagram Description: A schematic of a 4-pipe defrost system. It includes an evaporator, solenoid valves, and a separate defrost line. Key components labeled are A (ICFD drain module), B (ICFE solenoid valve module), and C (ICFC or ICFN check valve). Lines indicate flow paths: Wet return line, Defrost line, Liquid feed line, and Hot gas line.

• A: ICFD (drain module) is the main function of the Liquid drain.
• B: ICFE (solenoid valve module) closes the drain line during freezing mode.
• C: ICFC or ICFN (check or stop check valve) prevents backflow from the separate defrost drain line into the low-temperature liquid line during freezing mode.

Notice: The capacity of the ICFD-liquid drain valve is not significantly affected compared to the solution with a "loaded check valve" due to the low pressure drop in standard check valves.

Multiple Evaporators Connected to a Common ICF Evaporator Station

Figure 5 illustrates a defrost system with two evaporators connected to a single common valve station. For proper operation, it is essential that the freezers are equally loaded and that refrigerant flow is distributed equally. Evaporators should be installed at equal heights and equipped with a deep liquid trap (P-trap) to prevent gas from one evaporator from blocking liquid flow from another.

Figure 5: Multiple evaporators connected to the same evaporator station

Diagram Description: A schematic showing two evaporators connected to a common valve station. Components labeled are A (Adjusting/balancing valves for refrigerant flow), B (Adjusting/balancing valves for hot gas flow), and C (Deep liquid trap (P-trap)). Lines indicate flow paths: Wet return line, Liquid feed line, and Hot gas line.

• A: Adjusting/balancing valves to ensure equal refrigerant flow.
• B: Adjusting/balancing valves to ensure equal hot gas flow.
• C: Deep liquid trap (P-trap).

Protection of Evaporators Against Excessive Pressure Caused by Trapped Liquid

Figure 6 depicts a defrost system with two solenoid valves (liquid feed and wet return lines) but none in the liquid drain line. In this setup, the ICFD drain module and loaded check valve (ICFC 20P1) act as the pressure barrier between the evaporator pressure and the wet return line pressure (liquid separator).

When using an ICFC 20P1 loaded check valve without additional solenoid valves, it can protect evaporators against excessive pressure from trapped liquid. The liquid drain valve, connected to the evaporator's bottom, ensures all liquid is drained during continuous heat input, preventing unintended pressure increases.

Figure 6: Evaporator station with ICFC 20P1 loaded check valve and the ICFD drain module preventing excessive pressure caused by trapped liquid in evaporator

Diagram Description: A schematic illustrating a system with an evaporator protected by an ICFD "Liquid float valve" and an ICFC 20P1 "Loaded check valve". Solenoid valves are marked as "O" (Operation) and "S" (Service). The diagram highlights the pressure barrier function of the ICFC 20P1.

If the evaporator pressure exceeds the liquid separator pressure by more than 0.5 bar, the loaded check valve (ICFC 20P1) opens, allowing liquid to flow to the ICFD drain module. Systems with a liquid drain valve and a loaded check valve in the drain line are protected against trapped liquid.

Mtv (max trapped volume for ICFD + ICFC 20 P1):

Mtv = 883.23*Kv100 [l] = 883.23*1.116 = 985 Liters (at Kv of 1.116 m³/h)

Note: The drain valve features a built-in parallel bleed orifice (ø 1.25 mm ~ Kv = 0.064 m³/h).

For defrost systems with three solenoid valves (liquid feed, wet return, and liquid drain lines), evaporators must be adequately protected against excessive pressure caused by trapped liquid.

Installation

Figures 7 to 9 showcase common evaporator types. For systems designed with the ICFD liquid drain method, all evaporator types must connect to the ICF valve station using the same piping configuration.

• Condensate drain outlet should be at the lowest pipe of the evaporator.
• Hot gas inlet should be at the top pipe of the evaporator.

The ICFD module is primarily designed for liquid drainage. Initial gas in the system during the defrost process is drained through a small parallel bleed orifice within the ICFD module. Ensuring all liquid is drained from the evaporator during the defrost sequence is critical for proper defrosting.

Figure 7: Bottom feed

Diagram Description: An evaporator with a bottom feed configuration, showing hot gas inlet at the top and condensate drain at the bottom. Arrows indicate flow direction.

Figure 8: Top feed with distribution nozzles

Diagram Description: An evaporator with a top feed configuration and distribution nozzles. Hot gas inlet is at the top, and condensate drain is at the bottom. Arrows indicate flow direction.

Figure 9: Side/bottom feed with distribution nozzles

Diagram Description: An evaporator with a side/bottom feed configuration and distribution nozzles. Hot gas inlet is at the top, and condensate drain is at the bottom. Arrows indicate flow direction.

Drain line

During piping layout, minimize pressure drop to prevent flash gas. Pressure loss can reduce liquid drain capacity.

For evaporators with distribution nozzles at the drain outlet (side/bottom feed in Figure 9), the liquid passing through the nozzles during defrost creates a pressure drop in the drain line. This pressure drop must be considered to minimize the total pressure drop. The liquid's lifting height should not exceed 5 m (16.5 ft).

The Danfoss selection tool Coolselector 2 is recommended for calculating the total pressure drop for ICF systems including ICFD.

Always install a P-trap at the drain line connection to the evaporator to collect liquid. A separate line for the defrost drain (Figure 10) is the optimal piping layout. This allows for optimized liquid velocity and volume, reducing pressure loss. Figure 11 presents alternative piping layouts. Using the existing liquid line is acceptable if a P-trap is installed.

During piping layout, minimize pressure drop in the hot gas line to ensure sufficient defrost pressure (temperature) in the evaporator. Pressure loss can reduce defrost capacity.

For evaporators with distribution nozzles at the hot gas entrance (top feed in Figure 8), the gas passing through the nozzles during defrost creates a pressure drop in the hot gas line. This must be considered when determining total pressure loss.

The Danfoss selection tool Coolselector 2 is recommended for calculating and optimizing pressure losses in both liquid drain and hot gas lines.

The ICFD liquid drain setup does not control pressure during defrost. If the hot gas supply pressure exceeds the defrosting requirement, it is recommended to install a pressure-reducing valve (e.g., ICS/CVC) before the hot gas valve station to prevent excessive pressure that could damage the evaporator. The CVC should be set to the intended defrost pressure.

Figure 10: Best solution (Optimized liquid velocity and volume). Always install P-trap

Diagram Description: A schematic illustrating the recommended piping layout for liquid drain and hot gas lines. It shows an evaporator, ICFD module, P-trap, and control valves (BSV, ICS, CVC). Key lines are Wet return, Liquid drain, and Hot Gas. The diagram indicates a maximum vertical distance (riser height) of 5 m (16.5 ft) between the ICFD inlet and the evaporator bottom.

Figure 11: Possible solution. Always install P-trap

Diagram Description: A schematic showing an alternative piping layout for liquid drain and hot gas lines, including an evaporator, ICFD module, P-trap, and control valves. Key lines are Wet return, Liquid line/(Liquid drain), and Hot Gas. The diagram indicates a maximum vertical distance (riser height) of 5 m (16.5 ft) between the ICFD inlet and the evaporator bottom.

Online Support

For further information and support, please refer to Danfoss resources.