**Abstract:** This paper presents and analyzes three application schemes for differential pressure control valves in a dual-pipe household heating system, along with the principles for selecting each scheme. It emphasizes that under design conditions, the natural pressure head in a dual-pipe heating system with household metering should not be considered. The paper also highlights the importance of using different strategies for indoor and outdoor systems. Keywords: pressure control valve; household heat metering; dual-pipe heating system. **I. Introduction** In a dual-pipe household heating system with metering, thermostatic valves are typically installed on each group of radiators to take advantage of free heat from appliances, lighting, and human activity. This leads to a variable flow system where the pressure difference across the temperature control valves changes with flow rate. If the actual pressure difference is too high, it can cause noise, especially when the heat load is low, leading to frequent switching and oscillation. This not only causes wear but also affects the return water temperature and other thermostatic valves. Therefore, in a well-designed system, the thermal power of the thermostatic valve must always be greater than or equal to 1, and the actual pressure difference should remain within its allowable range. A differential pressure control valve, also known as a self-actuated differential pressure control valve, helps maintain a constant pressure difference in the controlled loop, ensuring stable operation of the temperature control valves. In a dual-pipe heating system, there are generally three common installation schemes for these valves: a. Installing the differential pressure control valve only at the building’s heating inlet to regulate the pressure drop at that point. b. Placing the valve at the start of each riser in a two-pipe system to control the pressure difference of the riser. c. Locating the valve at the inlet of each household to maintain a constant indoor pressure. While each option has its advantages and disadvantages, the choice depends on system size, cost, and performance requirements. This paper provides an in-depth analysis of each scheme, aiming to guide engineers in making informed decisions during the design process. **II. Scheme Analysis** **1. Option 1: Differential Pressure Control Valve at the Building's Heating Inlet** In this configuration, the differential pressure control valve regulates the pressure drop at the building’s main heating inlet. The pressure difference (ΔPS) acting on the household inlet is calculated as: ΔPS = ΔP1 + ΔP2 - ΔP3 Where: - ΔP1 is the controlled pressure difference at the building inlet. - ΔP2 is the natural pressure head caused by the height difference between supply and return pipes. - ΔP3 is the resistance loss from the control point to the user inlet. Under design conditions, the natural pressure head (ΔP2) should be taken as the minimum value to ensure that the actual pressure difference on the thermostat valve does not fall below the required level. However, in practice, due to varying natural pressure heads, it may be more practical to ignore ΔP2 during initial design calculations. The key challenge here is to ensure that the pressure difference at the household inlet remains above the total resistance of the indoor system. This can be achieved through proper hydraulic calculations during the design phase. **2. Option 2: Differential Pressure Control Valve at Each Common Riser** This option is suitable for a two-pipe system where the pressure difference on each riser is controlled individually. Similar to Option 1, the pressure difference (ΔP1) should be set based on the most adverse loop on the riser. The maximum allowable pressure difference is generally around 30 kPa to prevent damage to the thermostatic valves. However, if the calculated ΔP1 exceeds this limit, this option may not be feasible. Careful hydraulic calculations are essential to ensure that the pressure difference remains within acceptable limits. **3. Option 3: Differential Pressure Control Valve at Each Household Inlet** This is the most effective option for large-scale heating systems. By placing the valve at the household level, the indoor system can maintain a constant pressure, regardless of fluctuations in the outdoor system. The pressure difference (ΔP1) should be set to match the total resistance of the most adverse indoor loop, including the heat meter and lock-up valve. It is crucial that the pressure difference does not exceed 30 kPa to avoid overloading the valves. Additionally, the outdoor system should be designed with a separate pressure control mechanism if the inlet pressure exceeds the valve’s maximum working pressure. **III. Conclusion** 1. During hydraulic calculations for a dual-pipe household heating system with metering, the natural pressure head should not be considered. Indoor and outdoor systems should use different strategies. 2. For Option 1, the control pressure difference (ΔP1) should equal the total resistance of the most adverse loop and should not exceed 30 - gH(ρh - ρg)/1000 kPa. 3. For Option 2, the control pressure difference should also be limited to 30 - gH(ρh - ρg)/1000 kPa. 4. Option 3 is best suited for large systems, where the control pressure difference should match the indoor system’s total resistance and stay below 30 kPa. By carefully analyzing these options, engineers can select the most appropriate scheme for their specific project, ensuring both efficiency and reliability in the heating system.

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