The Belimo Z2050Q-F+CQKB24-SR-LL is a 2-way, 1/2″ NPT ZoneTight ball zone valve (Cv 1.4, 75 psi close-off, 0% leakage) factory-assembled with the CQKB24-SR-LL, an electronic fail-safe actuator that drives the valve to 100% open on loss of power. The actuator runs on AC/DC 24 V and accepts a modulating 2...10 V control signal (4...20 mA with the ZG-R01 500 Ω resistor) and provides 2...10 V position feedback. Belimo designates this model normally open: 2 VDC = open, 10 VDC = closed.
Specifications on this page are taken from the Belimo Z2050Q-F+CQKB24-SR-LL assembly technical data sheet (valve section revision 2024-06-12, CQKB24-SR-LL actuator section revision 2024-06-27), the CQK quick-mount instruction manual 71775-00001.L, the belimo.com product page for the normally open / normally closed designation and the Belimo ZoneTight brochure (PF_37, 05/25). Verified 2026-09-09.
Unit ventilators, fan coil units, VAV reheat coils, fin tube casing, radiant panels and duct coils in large commercial buildings (Belimo's listed QCV applications), with modulating zone control from a controller supplying 2...10 V (or 4...20 mA via the ZG-R01 resistor) where the coil must fail open on power loss. Belimo lists the QCV for installations where higher close-off and the ability to change flow are desired, in space-restricted areas.
Key Features
Zero Leakage Shutoff
Belimo publishes a 0% leakage rate and a 75 psi close-off pressure for the Z2050Q-F, with a 360 psi body rating.
Field-Adjustable Maximum Flow
An end-stop clip on the actuator changes the angle of rotation in 2.5° increments to set the maximum flow, from Cv 0.1 up to the full Cv 1.4, without tools.
Tool-Free Snap Assembly
The actuator plugs onto the valve by hand in vertical movements only; pins must match the holes on the flange. Mounting orientation can be selected in 180° increments.
Electronic Fail-Safe
On loss of power the actuator drives the valve to 100% open in under 60 s (published fail-safe running time), with a 2 s bridging time and 5...20 s pre-charging time.
Modulating with Position Feedback
2...10 V operating range with 2...10 V position feedback; 4...20 mA control with the ZG-R01 500 Ω resistor. This model is normally open: 2 VDC = open, 10 VDC = closed.
Plenum Rated, cULus Listed
UL 2043 compliant for use in air plenums per NEC 300.22(C) and IMC 602; cULus listed to UL60730-1A/-2-14 and CAN/CSA E60730-1:02, UL Enclosure Type 2 / NEMA 2 / IP40.
Technical Specifications — Valve
| Specification | Detail |
|---|---|
| Valve Type | ZoneTight (QCV) ball zone valve, 2-way |
| Valve Size | 1/2″ [DN 15] |
| Pipe Connection | Internal thread, NPT (female) |
| Cv | 1.4 |
| 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 |
| Angle of Rotation | Operating range 15...90° |
| Controllable Flow Range | 75° |
| Flow Direction | Direction of flow in both directions possible |
| Installation Orientation | Upright to horizontal (in relation to the spindle); not in a hanging position with the stem pointing downwards |
| Servicing | Maintenance-free |
| Valve Body | Forged brass |
| Stem | Brass |
| Stem Seal | EPDM O-ring |
| Seat | PTFE, O-ring EPDM |
| O-ring | EPDM (lubricated) |
| Ball | Chrome plated brass |
| Suitable Actuators | Non fail-safe CQB(X); electronic fail-safe CQKB(X) |
| Valve Weight | 0.31 lb [0.14 kg] (TDS rev 2026-02-07); 0.15 lb [0.070 kg] (2024-06-12 revision) — see note |
| Assembly Dimensions (CQK actuator) | A 4.5″ [114] · B 2.0″ [52] · C 3.3″ [83] · D 2.7″ [69] · E 0.9″ [24] · F 0.9″ [24] — drawing on data sheet p. 3 |
| Field Flow Setting (end-stop clip) | position 1 = Cv 0.1; position 3- = Cv 0.2; position 4+ = Cv 0.4; position 5+ = Cv 0.6; position 6 = Cv 0.8; position N = Cv 1.2; position No end stop = Cv 1.4 (V'nom) |
Technical Specifications — CQKB24-SR-LL Actuator
| Specification | Detail |
|---|---|
| Actuator | CQKB24-SR-LL — Modulating, Electronic fail-safe, 24 V, ZoneTight CQK family |
| Control | Modulating 2...10 V (4...20 mA with ZG-R01 500 Ω resistor) |
| Signal Direction | 2 VDC = open, 10 VDC = closed |
| Fail-Safe Position | 100% open |
| 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 GA plenum cable, 3 ft [1 m], with 1/2″ NPT conduit connector |
| Overload Protection | electronic throughout 0...90° rotation |
| Electrical Protection | actuators are double insulated |
| Operating Range Y | 2...10 V |
| Operating Range Y (note) | 4...20 mA w/ ZG-R01 (500 Ω, 1/4 W resistor) |
| Position Feedback U | 2...10 V |
| Bridging Time (PF) | 2s |
| Pre-charging Time | 5...20 s |
| Angle of Rotation | 90°, adjustable with mechanical stop |
| Running Time (Motor) | 75 s / 90° |
| Running Time Fail-Safe | <60 s |
| Noise Level, Motor | 35 dB(A) |
| Noise Level, Fail-Safe | 35 dB(A) |
| Position Indication | pointer |
| 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 | 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] |
| Manufacturer | Belimo |
| Manufacturer Part Number | Z2050Q-F+CQKB24-SR-LL |
| Warranty | 5 years |
Documentation
Belimo Z2050Q-F+CQKB24-SR-LL Technical Data Sheet (actuator rev 2024-06-27)- CQK Actuator Quick Mount Instructions with ZoneTight Zone Valves (71775-00001.L)
- Belimo ZoneTight Zone Valves Brochure
- Belimo ZoneTight Zone Valve Guide Specification (Section 230900)
Related Products
- Belimo Z2050Q-F — valve body only, actuator sold separately
- Belimo Z2050Q-F+CQKB24-LL — 24 VAC/DC, On/Off, fails open
- Belimo Z2050Q-F+CQKB24-RR — 24 VAC/DC, On/Off, fails closed
- Belimo Z2050Q-F+CQKB24-S-LL — 24 VAC/DC, On/Off, fails open, aux switch
- Belimo Z2050Q-F+CQKB24-S-RR — 24 VAC/DC, On/Off, fails closed, aux switch
Frequently Asked Questions
What is the Belimo Z2050Q-F+CQKB24-SR-LL?
It is Belimo's Z2050Q-F 2-way 1/2″ NPT ZoneTight zone valve (Cv 1.4) supplied as a factory assembly with the CQKB24-SR-LL electronic fail-safe actuator, which accepts a modulating 2...10 V control signal (4...20 mA with the ZG-R01 500 Ω resistor) and provides 2...10 V position feedback and runs on AC/DC 24 V.
What happens on loss of power?
The CQKB24-SR-LL is electronic fail-safe: Belimo publishes a fail-safe running time of under 60 s to 100% open, with a 2 s bridging time and a 5...20 s pre-charging time after power-up.
What transformer or supply does the CQKB24-SR-LL need?
Belimo lists a nominal voltage of AC/DC 24 V (range AC 19.2...28.8 V / DC 21.6...28.8 V, 50/60 Hz), transformer sizing 5 VA, power consumption 2.5 W in operation and 0.5 W at rest. Actuators may be connected in parallel; power consumption and input impedance must be observed.
What control signal does the CQKB24-SR-LL accept?
Modulating 2...10 V, with 2...10 V position feedback. A 500 Ω ZG-R01 resistor converts a 4...20 mA control signal to 2...10 V. This model is normally open: 2 VDC = open, 10 VDC = closed.
Can the maximum flow of the Z2050Q-F be adjusted in the field?
Yes. The actuator end-stop clip changes the angle of rotation in 2.5° increments; published Z2050Q(S)-F positions are position 1 = Cv 0.1; position 3- = Cv 0.2; position 4+ = Cv 0.4; position 5+ = Cv 0.6; position 6 = Cv 0.8; position N = Cv 1.2; position No end stop = Cv 1.4 (V'nom). On modulating actuators an adaptation must be triggered after any clip change.
Is the CQKB24-SR-LL rated for plenum installation?
Yes. Belimo lists it as UL 2043 compliant and suitable for use in air plenums per NEC Section 300.22(C) and IMC Section 602, with UL Enclosure Type 2 / NEMA 2 / IP40 protection.
What is the warranty on the Z2050Q-F+CQKB24-SR-LL?
Belimo warrants ZoneTight components for 5 years from the date of production. Belimo notes the warranty is invalidated if the fluid exceeds 212°F due to a boiler control failure.
- Valve Pattern:
- 2-Way
- Valve Size:
- 1/2 Inch
- Connection Type:
- NPT
- CV Rating:
- 1.4
- Actuator Type:
- Fail-Safe
- Voltage:
- 24VAC/DC
- Control Signal:
- 2-10VDC
- Auxillary Switch:
- None
