Siemens VPI46 Combi Valve PICV DN 15-50, Internally Threaded PN 25

Overview

The Siemens VPI46 is the internally threaded combi valve of the Siemens Acvatix range: a compact pressure independent control valve (PICV) that combines a control valve, a flow presetting dial and a mechanical differential pressure controller in one body. It is used for water-side control and automatic hydronic balancing of terminal units such as fan coils, induction units and heat exchangers for heating or cooling, and for heating zones in apartments and individual rooms. Siemens offers the VPI46 with Rp threads to ISO 7-1 from DN 15 to DN 50, with presettable flows from 30 l/h up to 11500 l/h, while the externally threaded twin VPP46 covers DN 10 to DN 32.

Seven Star LLC supplies the Siemens VPI46 and VPI46..Q to fan coil manufacturers, MEP contractors and maintenance teams across Oman and the GCC, together with compatible thermal and motorised actuators. Our engineering team in Muscat can select the right size and flow variant from a fan coil schedule and calculate the dial setting for each unit before delivery.

Operating Principle

Water entering the Siemens VPI46 at inlet port A first passes the variable presetting opening, which is linked to the ring with the presetting dial. It then flows through the control valve, which has a linear characteristic and a stroke of 2.5 mm, 5 mm, 5.5 mm or 15 mm depending on size, and is positioned by the actuator. Before leaving the valve, the water passes the built-in mechanical differential pressure controller, which Siemens describes as the heart of the PICV. The controller keeps the pressure difference across the control valve and the presetting constant, so the selected volumetric flow is maintained across the whole working range regardless of the inlet pressure.

In practice this means that a fan coil fitted with a Siemens VPI46 receives its design flow whether it is next to the pump or on the top floor, and that closing other units does not push extra water through it. The ..Q versions add two pressure test points, P+ with a red ribbon and P- with a blue ribbon, for measuring the differential pressure across the valve with the Siemens ALE10 electronic manometer. Comparing this reading with the minimum required differential pressure from the presetting table tells the commissioning engineer whether the valve is working inside its pressure independent range.

Engineering Design of the Siemens VPI46

From DN 15 to DN 32 the Siemens VPI46 body, ports, seat, sealing gland and test points are made of dezincification resistant hot-pressed brass CW602N; DN 40 and DN 50 bodies are nodular cast iron. The stem and spring are stainless steel, the regulator is PPS, the presetting element uses PTFE, PPO, POM C and ABS, and the O-ring seals are EPDM. The valve is rated PN 25 to EN 1333 with a permissible operating pressure of 2500 kPa, a maximum differential pressure of 800 kPa, and a medium temperature of 1 to 120 degrees C with actuator (1 to 110 degrees C with SUA21/3P and SUE21P). Leakage is Class IV to EN 1349, with Class III for DN 25 to 32 with STA..3.. actuators.

For Siemens VPI46 sizes DN 15 to 32 a manual control knob is fitted at the factory to protect the stem and presetting mechanism and to allow manual operation during commissioning; valves are supplied fully open so the system can be flushed. Presetting is done by removing the knob, loosening the knurled nut and turning the white dial. Siemens recommends mounting in the return pipe, fitting a strainer upstream and following VDI 2035 water treatment. EPP or EPE insulation covers are available for chilled water service, which is important in humid Gulf ceiling voids.

Key Features

Engineers specify the Siemens VPI46 for the following reasons:

• Control, presetting and differential pressure control combined in one internally threaded body, with no separate balancing valve needed.
• Sizes DN 15 to DN 50 with Rp 1/2 to Rp 2 threads, and nominal flows from 200 l/h to 11500 l/h.
• Wide operating range up to 800 kPa differential pressure, with a minimum of around 15 kPa on small sizes.
• Average flow accuracy of plus or minus 10 percent up to 2.5 times the minimum differential pressure, and plus or minus 5 percent above that up to 800 kPa.
• Optional ..Q versions with P/T test points for flow verification and pump optimisation.
• Compatible with thermal actuators STA../STP.., motorised SSA.., SSD..UT, SUA21/3P, SUE21P, and SAY..P03 on DN 40 and 50.
• DZR brass body for DN 15 to 32, resistant to dezincification in treated chilled water.
• Maintenance-free design with factory-fitted manual knob for commissioning.

Industrial Applications

The Siemens VPI46 is designed for the terminal level of HVAC systems: fan coil units, induction units, chilled beams, small air handling coils and plate heat exchangers. In Oman most commercial buildings are cooled by chilled water fan coils, and a hotel or hospital wing can contain hundreds of them. A Siemens VPI46 at each unit keeps flows stable when variable speed pumps slow down at night or when guest rooms switch off, which protects chiller delta-T and reduces pump energy. Typical projects include hotels and serviced apartments in Muscat, hospital extensions, schools, government buildings and residential towers connected to district cooling.

The DN 40 and DN 50 Siemens VPI46 sizes extend the same principle to larger fan coils, fresh air handling units and heat exchangers in mixed-use developments in Sohar, Duqm and Salalah. Seven Star LLC supplies the Siemens VPI46 with matching actuators and fittings and can provide flow setting tables per unit, helping contractors in the GCC commission faster and document results for handover.

Technical Specifications

The following Siemens VPI46 data is taken from the Siemens VPP46/VPI46 PICV PN 25 data sheet (document CE1N4855en) on the Siemens information portal:

How to Order

To request the Siemens VPI46 for your project, send Seven Star LLC a fan coil schedule or a formal RFQ. Our instrumentation division in Muscat will confirm the Siemens VPI46 size, flow variant and actuator, share the technical data, and arrange supply with engineering support for Oman and the GCC. For comparison or system completion, see the Danfoss AB-QM PICV, the Schneider Electric TAC Xenta building controller and the Grundfos MAGNA3 circulator pump.