The Belimo Z2050QS-F+CQKB24-SR-LR is a 1/2 in. sweat, 2-way ZoneTight (QCV) zone valve assembly that pairs the Z2050QS-F valve (Cv 1.4, 0% leakage) with the CQKB24-SR-LR electronic fail-safe actuator for 2...10 V modulating control at AC/DC 24 V.
The ball valve closes off against 75 psi and handles chilled or hot water with up to 60% glycol from 36 to 212°F. The body is forged brass with a chrome plated brass ball and a 360 psi body pressure rating. On loss of power the CQKB24-SR-LR drives the valve to its fail position, with a fail-safe running time under 60 s. It accepts a 2...10 V control signal, or 4...20 mA with a ZG-R01 500 Ω resistor, and returns a 2...10 V position feedback signal.
Best For
- Unit ventilators
- Fan coil units
- VAV reheat coils
- Fin tube casing
- Radiant panels
- Duct coils
- Closed water systems in large commercial buildings where higher close-off and the ability to change flow is needed
- Space-restricted installations
Warranty
Belimo warrants all ZoneTight valve and actuator components for 5 years from the date of production. If the water temperature exceeds the 212°F operating range because of a boiler control failure, the valve will safely contain the hot water but the manufacturer warranty becomes invalid.
ZOT Supply is an authorized Belimo distributor. Every Z2050QS-F+CQKB24-SR-LR ships as genuine Belimo product, with nationwide shipping.
Key Features
0% leakage ball valve
Belimo ball valve design with 0% leakage (A to AB), an equal percentage characteristic and a Cv of 1.4.
Field-adjustable maximum flow
The end stop clip changes the angle of rotation in 2.5° increments, setting the maximum Cv from 0.1 to 1.4. After a clip change, an adaptation must be triggered on the modulating actuator.
Tool-free snap assembly
The actuator plugs onto the valve by hand, with the mounting orientation selectable in 180° increments.
Electronic fail-safe
Fail-safe running time under 60 s with 5...20 s pre-charging time.
Modulating with feedback
2...10 V control (4...20 mA with ZG-R01 resistor) and 2...10 V position feedback.
Plenum rated
UL 2043 compliant for use in air plenums per NEC Section 300.22(C) and IMC Section 602.
Technical Specifications
Valve
| Valve model | Z2050QS-F |
| Valve type | ZoneTight (QCV) zone valve, 2-way, sweat |
| Cv (no end stop) | 1.4 |
| Nominal size | 1/2 in. [DN 15] |
| Pipe connection | Sweat |
| Flow pattern | 2-way |
| Flow characteristic | Equal percentage |
| Leakage rate | 0% |
| Fluid | Chilled or hot water, up to 60% glycol |
| Fluid temperature range (water) | 36...212°F [2...100°C] |
| Body pressure rating | 360 psi |
| Close-off pressure (Δps) | 75 psi |
| Differential pressure (Δpmax) | 40 psi |
| Operating range (angle of rotation) | 15...90° |
| Controllable flow range | 75° |
| Flow direction | Both directions possible |
| Installation orientation | Upright to horizontal (in relation to the spindle); not hanging with the stem pointing downwards |
| Valve body | Forged brass |
| Ball | Chrome plated brass |
| Stem | Brass |
| Stem seal | EPDM O-ring |
| Seat | PTFE, O-ring EPDM |
| O-ring | EPDM (lubricated) |
| Servicing | Maintenance-free |
| Valve weight | 0.37 lb [0.17 kg] |
Actuator
| Actuator model | CQKB24-SR-LR |
| Actuator type | Modulating, Electronic fail-safe, 24 V |
| Nominal voltage | AC/DC 24 V |
| Nominal voltage frequency | 50/60 Hz |
| Nominal voltage range | AC 19.2...28.8 V / DC 21.6...28.8 V |
| Power consumption in operation | 2.5 W |
| Power consumption in rest position | 0.5 W |
| Transformer sizing | 5 VA |
| Electrical connection | 22 AWG plenum cable, 1 m, with 1/2" NPT conduit connector |
| Operating range Y | 2...10 V |
| Operating range Y, 4...20 mA | 4...20 mA w/ ZG-R01 (500 Ω, 1/4 W resistor) |
| Input impedance | 100 kΩ for 2...10 V (0.1 mA), 500 Ω for 4...20 mA |
| Feedback signal U | 2...10 V |
| Bridging time (PF) | 2 s |
| Pre-charging time | 5...20 s |
| Angle of rotation | 90° |
| Angle of rotation adjustment | adjustable with mechanical stop |
| Running time (motor) | 75 s / 90° |
| Running time (fail-safe) | <60 s |
| Sound power level, motor | 35 dB(A) |
| Sound power level, fail-safe | 35 dB(A) |
| Visual indicator | pointer |
| Overload protection | electronic throughout 0...90° rotation |
| Electrical protection | actuators are double insulated |
| Power source UL | Class 2 Supply |
| Degree of protection IEC/EN | IP40 |
| Degree of protection NEMA/UL | NEMA 2 |
| Enclosure | UL Enclosure Type 2 |
| Agency listing | cULus acc. to UL60730-1A/-2-14, CAN/CSA E60730-1:02; CE acc. to 2014/30/EU and 2014/35/EU |
| Quality standard | ISO 9001 |
| UL 2043 compliant | Suitable for use in air plenums per Section 300.22(C) of the NEC and Section 602 of the IMC |
| Ambient humidity | Max. 95% RH, non-condensing |
| Ambient temperature | 35...104°F [2...40°C] |
| Storage temperature | -40...176°F [-40...80°C] |
| Housing material | UL94-5VA |
| Actuator weight | 0.55 lb [0.25 kg] |
Maximum Cv by end stop clip position
| Clip position | 1 | 3- | 4+ | 5+ | 6 | N | No end stop |
|---|---|---|---|---|---|---|---|
| Max Cv | 0.1 | 0.2 | 0.4 | 0.6 | 0.8 | 1.2 | 1.4 |
| Runtime (s) | 30 | 41 | 51 | 58 | 62 | 68 | 75 |
Safety: California Proposition 65 warning, this product can expose you to chemicals including lead. Do not install the valve hanging with the stem pointing downwards.
Specifications per Belimo Z2050QS-F technical data sheet rev 2026-07-15, CQKB24-SR-LR technical data sheet rev 2025-12-24, CQK Quick Mount manual 71775-00001.L, Belimo zone valve guide specification rev July 22, 2025. Reviewed 2026-09-23.
Documentation
FAQ
What is the Cv of the Belimo Z2050QS-F+CQKB24-SR-LR?
The Z2050QS-F+CQKB24-SR-LR has a Cv of 1.4 with no end stop. The end stop clip reduces the maximum Cv in steps down to 0.1 at clip position 1.
Can the Z2050QS-F+CQKB24-SR-LR be controlled with 4-20 mA?
Yes. The CQKB24-SR-LR accepts 2...10 V directly, or 4...20 mA with a ZG-R01 500 Ω, 1/4 W resistor, and provides a 2...10 V feedback signal.
What transformer size does the Z2050QS-F+CQKB24-SR-LR need?
Size the transformer at 5 VA per CQKB24-SR-LR actuator on AC/DC 24 V supply.
What is the close-off pressure of the Z2050QS-F+CQKB24-SR-LR?
The Z2050QS-F+CQKB24-SR-LR closes off against 75 psi, with a 40 psi maximum differential pressure and a 360 psi body pressure rating.
Can the Z2050QS-F+CQKB24-SR-LR be installed with the stem pointing down?
No. Install the valve upright to horizontal; it may not be installed hanging with the stem pointing downwards.
- Valve Pattern:
- 2-Way
- Valve Size:
- 1/2 Inch
- Connection Type:
- Sweat
- CV Rating:
- 1.4
- Actuator Type:
- Fail-Safe
- Voltage:
- 24VAC/DC
- Control Signal:
- 2-10VDC
- Auxillary Switch:
- None
