Two-way control valve VM2 DN20 Kvs 4.0
Where the VM2 DN20 Kvs 4.0 is used
The Danfoss VM2 is a two-way seated control valve for district heating substations and other units where flow must be controlled precisely over a long service life. DN 20 with Kvs 4.0 m³/h suits domestic hot water circuits with a heat exchanger or storage water heater, and low-output heating circuits in an independently connected substation. The body is red bronze (Rg 5), the cone, seat and stem stainless steel, so the valve handles network water up to 150 °C and glycol solutions up to 30 %.
The design is pressure balanced: medium pressure acts on both sides of the cone, so little force is needed to close — with a compact AMV(E) actuator the valve closes against a differential pressure of 25 bar. The second feature is the SPLIT characteristic: flow changes gently over the first part of the stroke, so control stays stable even at low loads. Rangeability exceeds 50:1 and leakage in the closed position stays within 0.05 % of Kvs to IEC 534.
Technical specifications
| Danfoss code | 065B2016 |
| Type | VM 2, two-way seated control valve |
| Nominal diameter | DN 20 |
| Kvs | 4.0 m³/h |
| Pressure class | PN 25 |
| Connection | external thread G 1 A (ISO 228-1) |
| Stroke | 5 mm |
| Medium temperature | 2…150 °C |
| Medium | circulation water or glycol solution up to 30 % |
| Closing differential pressure Δp | 25 bar (with AMV(E) 10/13, 20/23, 30/33) |
| Control characteristic | SPLIT |
| Rangeability | > 50:1 |
| Leakage (IEC 534) | max. 0.05 % of Kvs |
| Cavitation factor | ≥ 0.5 |
| Body material | red bronze (Rg 5) |
| Cone, seat, stem | stainless steel |
| Sealing | EPDM O-rings |
| Length L1 | 70 mm |
| Spanner size (SW) | 37 mm |
| Weight | 0.83 kg |
| Matching actuators | AMV(E) 10, 20, 30; with spring return AMV(E) 13, 23, 33 |
How to select
Kvs is selected from the design flow rate and the differential pressure. Flow: Q = P × 0.86 / Δt, where P is power (kW) and Δt the temperature difference (K). Then the required flow coefficient Kv = Q / √Δp, where Δp is the differential pressure across the valve (bar). Choose a valve whose Kvs is not lower than the calculated Kv.
Example: a 40 kW circuit, Δt = 20 K, Δp = 0.2 bar. Q = 40 × 0.86 / 20 = 1.72 m³/h; Kv = 1.72 / √0.2 ≈ 3.8 — DN 20 with Kvs 4.0 fits. An oversized Kvs opens the valve only at the very start of the stroke and control becomes unstable, so choosing "with a margin" is not worthwhile. When installing, the actuator must not point downwards.
When to choose it
- Domestic hot water preparation with a heat exchanger or storage water heater — stable temperature under varying draw-off.
- Independently connected substations with high network differential pressure — closes against up to 25 bar.
- Heating or cooling circuits running on glycol solutions up to 30 %.
- Units needing a safety function — spring-return AMV(E) 13/23/33.
Frequently asked questions
Which actuators fit the VM2 DN20 Kvs 4.0?
Danfoss AMV(E) 10, 20 and 30, or AMV(E) 13, 23 and 33 when spring return is required. With all of them the closing differential pressure reaches 25 bar. The actuator is fixed with a push-on clamp connection, with no adapters.
Do connection tailpieces have to be ordered separately?
Yes. The valve has an external G 1 A thread and connects to the pipework through DN 20 tailpieces: weld-on (code 003H6909) or with external thread (code 003H6903). Supplied separately.
How does the VM2 differ from the VB2?
The same family, with the same SPLIT characteristic and PN 25 rating. The difference is the connection: the VM2 has an external thread and a red bronze body, the VB2 flanges and a ductile iron body. In threaded pipework the VM2 is the usual choice.
Are spare parts available?
Yes. A replaceable valve insert is available — Danfoss code 065B2036. The same insert also fits the VM2 DN 15 Kvs 4.0, so the valve can be refurbished instead of replaced.