4-Way Valves - Danfoss & Dunan AC Reversing Valve

What Are 4-Way Valves? The Heart of the Air Conditioning System

4-way valves are critical components responsible for reversing the direction of the refrigerant, enabling heat pump and split air conditioner systems to switch from cooling mode to heating mode. Also known as reversing valves, these valves work like a traffic officer that decides whether the high-pressure gas leaving the compressor goes to the indoor unit or the outdoor unit. At Yedepa.com, for HVAC technicians, refrigeration technicians and service professionals, we keep in stock original products of the Danfoss and Dunan brands.

With the spread of inverter air conditioners, VRF systems and heat pump water heaters, the importance of 4-way valves increases every year. A valve with the right capacity and the right connection size directly affects system efficiency and also extends compressor life. A wrongly chosen 4-way valve, on the other hand, can lead to serious failures ranging from reduced cooling performance and refrigerant leaks to compressor burnout. In this guide we will explain 4-way valve types, the working principle, model selection and maintenance recommendations in technical language for our technicians.

Technical Details and Working Principle

A 4-way valve is a brass-bodied component that houses a pilot solenoid and main slide mechanism. There are four copper pipe connections on the valve: one goes to the compressor discharge line, one to the compressor suction line, one to the indoor unit heat exchanger and one to the outdoor unit heat exchanger. When the pilot solenoid is energized, a small pressure difference is created, and this difference shifts the main slide to the other side, reversing the direction of the refrigerant.

In cooling mode, the hot gas leaving the compressor is directed to the outdoor unit, the outdoor unit acts as the condenser and heat is rejected from inside. In heating mode, the solenoid is energized, the slide shifts and the hot gas is directed to the indoor unit; thus the indoor unit becomes the condenser and the outdoor unit the evaporator. For this mechanism to work properly, a clean circuit on the refrigerant side and a stable 220V AC coil supply on the electrical side are essential. Manufacturers usually specify the valve's operating temperature as between -30°C and +130°C; for example, the Danfoss STF-5002G3 model is certified to operate exactly in this range.

Types and Model Varieties

4-way valves are classified by capacity, connection size and the refrigerant type they are compatible with. We can broadly group the products sold at Yedepa.com as follows:

Small capacity (1-3 HP, 9,000-37,500 BTU): For mono split air conditioners and small commercial coolers, the Dunan DSF-4, DSF-9, DSF-9B and DSF-11B series stand out.
Medium capacity (3-5 HP, 36,000-68,000 BTU): The Dunan DSF-20 model is widely used in floor-standing air conditioners, cassette-type indoor units and small VRF outdoor units.
High capacity (5-15 HP, 116,000-170,000 BTU): The Dunan DSF-34H and DSF-50 models are preferred for commercial air conditioning systems, heat pumps and large VRF plants.
Industrial capacity (above 15 HP): The Danfoss STF-2011G3, STF-1511G3 and STF-5002G3 series are used in cold storage warehouses, chiller units and large industrial heat pumps.

In terms of refrigerant compatibility, the vast majority of modern valves are designed to work with R410A, R32 and R22. As the transition to the new-generation environmentally friendly refrigerant R32 accelerates while the service needs of old R22 systems continue, at Yedepa.com we keep products supporting both generations in stock.

About the Danfoss and Dunan Brands

Danfoss is a Denmark-based global giant that has been manufacturing refrigeration and air conditioning components since 1933. Its STF series 4-way valves are regarded as the reference solution in industrial applications and high-capacity heat pumps. Brass body workmanship, leak tightness tests and long-lasting solenoid coils are the technical features that make Danfoss stand out.

Dunan, although based in China, is an OEM supplier to major manufacturers such as Daikin, Midea and Gree in the global HVAC market. Thanks to its price-performance balance, the DSF series has become a series preferred especially by service technicians in the Turkish market. At Yedepa.com you can find a wide Dunan capacity range from 1 HP to 15 HP.

Which Model Should You Choose? Decision Guide

Choosing the right 4-way valve depends on three basic parameters: system capacity (BTU or HP), copper pipe connection sizes and refrigerant type. The comparison table below will help you make a quick decision among the products in Yedepa stock:

Model	Brand	Connection (Inlet x Outlet)	Capacity	Refrigerant
DSF-4	Dunan	5/16" x 3/8"	13,500 BTU	R410A/R32/R22
DSF-9 / DSF-9B	Dunan	3/8" x 1/2" - 5/8"	30,500 BTU	R410A/R32/R22
DSF-11B	Dunan	1/2" x 5/8"	37,500 BTU	R410A/R32/R22
DSF-20	Dunan	1/2" x 3/4"	68,000 BTU	R410A/R32/R22
DSF-34H	Dunan	3/4" x 7/8"	116,000 BTU	R410A/R32/R22
DSF-50	Dunan	7/8" x 1 1/8"	170,000 BTU	R410A/R32/R22
STF-2011G3	Danfoss	7/8" x 1 1/8"	Industrial	HFC/HCFC
STF-1511G3	Danfoss	7/8" x 1 1/8"	Industrial	HFC/HCFC
STF-5002G3	Danfoss	2 1/8" x 1 5/8"	Large Industrial	HFC/HCFC

If the air conditioner you service is a 9,000-12,000 BTU mono split, Dunan DSF-9 or DSF-9B will be ideal for you. For 18,000 BTU floor-standing air conditioners, DSF-11B should be preferred, and for larger 24,000-36,000 BTU systems, DSF-20. For commercial cassette and ducted air conditioners, DSF-34H is suitable, while for VRF outdoor units and heat pumps the DSF-50 or the Danfoss STF series is suitable.

4-Way Valves You Can Find at Yedepa.com

At Yedepa.com, we keep our original 4-way valve stock up to date across the full capacity range that HVAC technicians may need. Our featured models are listed below:

Danfoss STF-5002G3: 2 1/8" x 1 5/8" connection, -30°C to +130°C refrigerant temperature range, for large industrial heat pump and chiller applications.
Danfoss 061L1219 STF-2011G3: 7/8" x 1 1/8" connection, the reference solution for commercial air conditioning and medium-scale heat pump applications.
Danfoss 061L1224 STF-1511G3: 7/8" x 1 1/8" connection, a model whose compact structure makes service installation easier.
Dunan DSF-50: 7/8" x 1 1/8" connection, 13.9 m³/h flow, 170,000 BTU capacity — the economical solution preferred for VRF and heat pump outdoor units.
Dunan DSF-34H: 3/4" x 7/8" connection, 12.3 m³/h flow, 116,000 BTU — for the spare part needs of cassette and ducted indoor units.
Dunan DSF-20: 1/2" x 3/4" connection, 7.2-8.0 m³/h flow, 68,000 BTU — the most common choice for floor-standing air conditioners.
Dunan DSF-11B: 1/2" x 5/8" connection, 3.6 m³/h flow, 37,500 BTU — ideal for 18,000 BTU split air conditioners.
Dunan DSF-9B: 3/8" x 5/8" connection, 3.0 m³/h flow, 30,500 BTU — widely used in 12,000 BTU air conditioners.
Dunan DSF-9: 3/8" x 1/2" connection, 3.0 m³/h flow, 30,500 BTU — for compact indoor units with a small outlet size.
Dunan DSF-4: 5/16" x 3/8" connection, 1.7 m³/h flow, 13,500 BTU — the standard replacement for 9,000 BTU mono split air conditioners.

Professional Selection Criteria

Let us list the criteria that technicians should pay attention to when choosing a 4-way valve:

BTU or HP matching: The valve capacity should be close to the compressor capacity of the system. A valve that is too small creates a pressure drop, while a valve that is too large can prevent the slide from seating fully and cause internal leakage.
Connection diameter compatibility: The copper pipe sizes of the valve must match the system's gas (discharge) and liquid (suction) lines exactly. Using reducers should be a last resort.
Refrigerant compatibility: An R32-approved valve should be chosen for R32 systems and an R410A-approved valve for R410A. In old systems using R22, HCFC-compatible models should be preferred.
Solenoid voltage: A standard 220V AC 50Hz coil should be preferred for the Turkish market. Export products may have 110V coils, so care should be taken.
Certification: CE, UL and EN378 certified products should be preferred; cheap uncertified valves can develop internal leaks in a short time.
Mounting position: The 4-way valve must be mounted in the horizontal or vertical position specified by the manufacturer; a wrong position can disrupt the slide movement.

Usage and Maintenance Recommendations

There are very critical details to pay attention to during installation and maintenance for the 4-way valve to operate for a long time. When brazing, it is essential to wrap the valve body with a wet cloth and keep the internal temperature of the valve below 120°C; otherwise the Teflon and plastic seals inside melt and the slide becomes immobile.

A filter drier must always be used in the system, and before refrigerant charging the vacuum must be pulled down to 500 microns. Moisture remaining in the system oxidizes the copper parts inside the valve and causes the slide to clog. When replacing compressors, it is also recommended to check the 4-way valve, as old oil and metal chips may have settled inside the valve.

During service, when you encounter a stuck valve complaint, the first checkpoint is the solenoid coil. Measure the coil resistance with a multimeter (usually in the 1,000-1,500 ohm range). If the coil is sound, the main slide should be considered mechanically stuck; after the system pressure has equalized, a light tap or the reversing command should be repeated.

Frequently Asked Questions (FAQ)

Q1: What does a 4-way valve do?
A 4-way valve reverses the direction of the refrigerant in heat pumps and split air conditioners, allowing the system to switch between cooling and heating modes. Without this valve, the heating function of air conditioners does not work.

Q2: Which Dunan valve should I buy for my 12,000 BTU air conditioner?
For 12,000 BTU mono split air conditioners, the Dunan DSF-9 or DSF-9B is the most suitable choice. After checking the copper pipe size of your unit, you can quickly order through Yedepa.com.

Q3: Do I need to recharge the refrigerant when replacing the valve?
Yes. Replacing the valve requires the system to be completely emptied; after installing the new valve, a vacuum below 500 microns must be pulled and a fresh refrigerant charge in the amount recommended by the manufacturer must be made.

Q4: Can I use an R410A valve in my R32 air conditioner?
The vast majority of modern Dunan DSF series valves are manufactured to be compatible with R410A, R32 and R22. Still, be sure to check the label; old valves made only for R22 create a risk of bursting in high-pressure R410A/R32 systems.

Q5: What is the difference between Danfoss and Dunan?
Danfoss is a reference brand in industrial applications; its price is higher, but it leads in long life and certification. Dunan, as a global OEM supplier, stands out in price-performance balance; it is widely used in commercial and residential applications.

Q6: How can a 4-way valve failure be identified?
The most common symptoms are: the air conditioner blowing cold air in heating mode (or vice versa), being unable to switch between the two modes, abnormal noise from the outdoor unit and system pressures fluctuating between low and high. In these cases, first the solenoid coil and then the main slide should be checked.

Q7: How long does it take for a 4-way valve I order from Yedepa.com to arrive?
Danfoss and Dunan 4-way valves in stock at Yedepa.com are shipped throughout Turkey with contracted carriers. For products in stock, shipping is processed after order confirmation, and tracking information is sent by SMS and e-mail.

Conclusion and Yedepa Advantages

The 4-way valve is a critical component at the heart of air conditioning and heat pump systems that extends system life when chosen correctly but leads to expensive failures when chosen wrongly. For HVAC technicians and service technicians, choosing a valve with the right capacity, the right connection size and the right refrigerant compatibility is decisive for both customer satisfaction and service quality.

At Yedepa.com, we offer only original products of the industry's reference brands such as Danfoss and Dunan. For each product, the OEM code, fitment information, connection sizes and list of compatible refrigerants are shared in detail on the product page. We stand by our technicians in stock management, price transparency and technical support. Product comparison, finding equivalents and fast ordering processes for refrigeration technicians are among the standout advantages of Yedepa.com. For your 4-way valve needs, you can review our category page and place your order with confidence, making use of the technical details in the product descriptions.