The Belimo Z3050QS-E+CQKB24-S-LL is a ZoneTight (QCV) 3-way diverting zone valve assembly: a 1/2" sweat valve with a Cv of 1 and a linear flow characteristic, fitted with the CQKB24-S-LL electrical fail-safe, AC/DC 24 V actuator for on/off control.
The change-over valve fits in space-restricted areas, assembles without tools, and has a 0% leakage rate. Common applications include unit ventilators, fan coil units, VAV reheat coils, fin tube casing, radiant panels and duct coils.
Specifications: Belimo technical data sheet Z3050QS-E, dated 2025-01-09, and CQKB24-S-LL, dated 2024-03-15. Last reviewed 2026-10-09.
Best For
- Closed chilled and hot water systems, up to 60% glycol
- Switching functions and 2-point controls on the water side of air-handling units and heating systems
- Change-over duty where a 1/2" sweat valve with a Cv of 1 fits the design
- Zones that must go to a defined position on loss of power: fail position 100% Open
- AC/DC 24 V control circuits
- Systems that need an end-position contact for end position indication, interlock control, fan startup
Warranty
Belimo backs ZoneTight zone valves with a 5-year warranty.
If the temperature exceeds the 212°F operating range because of a boiler control failure, the valve safely contains the hot water, but the manufacturer's product warranty becomes invalid.
Key Features
Zero leakage
A 0% leakage rate, 40 psi close-off pressure and a 360 psi body pressure rating.
3-way diverting, linear
Linear flow characteristic with flow possible in both directions through the valve.
Tool-free snap assembly
The actuator plugs onto the valve by hand, with the mounting orientation selectable in 180° increments.
Electrical fail-safe
Goes to its 100% Open fail position on loss of power. Bridging time 2 s, pre-charging time 5...20 s, fail-safe running time <60 s.
Built-in auxiliary switch
One 1x SPST, 1 A resistive @ DC 30 V auxiliary switch for end position indication, interlock control, fan startup.
UL 2043, cULus listed
UL 2043 compliant for use in air plenums, double insulated, electronic overload protection throughout 0...90° rotation.
ZOT Supply is an authorized distributor of Belimo products.
Technical Specifications
| Valve: Belimo Z3050QS-E | |
|---|---|
| Valve size | 0.5" [15], DN 15 |
| Flow pattern | 3-way Diverting |
| Pipe connection | Sweat |
| Cv | 1 |
| Fluid | chilled or hot water, up to 60% glycol |
| Fluid temp range (water) | 36...212°F [2...100°C] |
| Body pressure rating | 360 psi |
| Close-off pressure Δps | 40 psi |
| Differential pressure Δpmax | 40 psi |
| Flow characteristic | linear |
| Leakage rate | 0% |
| Flow direction | both directions possible |
| Installation orientation | upright to horizontal (in relation to the spindle); not in a hanging position with the stem pointing downwards |
| Flow setting | remove the end stop clip at the actuator to get the 90° angle of rotation needed for change-over functionality |
| Mounting | tool-free snap assembly; mounting orientation selectable in 180° increments |
| Water quality | keep free from particle debris; installation of a suitable strainer is recommended |
| 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 | 0.4 lb [0.18 kg] |
| California Prop 65 | WARNING: This product can expose you to lead which is known to the State of California to cause cancer and reproductive harm. For more information go to www.p65warnings.ca.gov |
| Actuator: Belimo CQKB24-S-LL | |
|---|---|
| Actuator | CQKB24-S-LL: On/Off, Electrical fail-safe, 24 V |
| Fail 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 |
| Auxiliary switch | 1x SPST, 1 A resistive @ DC 30 V |
| Switching capacity auxiliary switch | 1 A resistive @ DC 30 V |
| 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 |
| Bridging time (PF) | 2 s |
| Pre-charging time | 5...20 s |
| Angle of rotation | 90° |
| Angle of rotation note | 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 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] |
| Actuator weight | 0.57 lb [0.26 kg] |
| Housing material | UL94-5VA |
| Auxiliary switch wiring | S1 / S2, NO |
| Installation note | Provide overload protection and disconnect as required. |
| Assembly dimensions with CQK actuator | |
|---|---|
| Dimension A | 4.5" [114] |
| Dimension B | 2.0" [52] |
| Dimension C | 3.8" [97] |
| Dimension D | 2.7" [69] |
| Dimension E | 1.0" [25] |
| Dimension F | 1.0" [26] |
Documentation
FAQ
What is the Cv of the Belimo Z3050QS-E+CQKB24-S-LL?
The Z3050QS-E valve has a Cv of 1, a 1/2" [DN 15] sweat connection and a linear flow characteristic.
Is the Z3050QS-E a mixing or diverting valve?
It is a 3-way diverting (change-over) zone valve. Flow is possible in both directions.
Does the actuator end stop clip need to be removed?
Yes. The end stop clip at the actuator has to be removed to get the 90° angle of rotation needed for change-over functionality.
What are the pressure and temperature limits?
Body pressure rating 360 psi, close-off pressure 40 psi, maximum differential pressure 40 psi, and fluid temperature 36...212°F [2...100°C] for chilled or hot water up to 60% glycol.
How must the valve be oriented?
Install it upright to horizontal. Do not install it hanging with the stem pointing downwards.
What power supply does the CQKB24-S-LL actuator need?
Nominal voltage AC/DC 24 V, 50/60 Hz (range AC 19.2...28.8 V / DC 21.6...28.8 V). Transformer sizing is 5 VA.
What position does the Z3050QS-E+CQKB24-S-LL go to on power loss?
The CQKB24-S-LL is an electrical fail-safe actuator with a fail position of 100% Open. Fail-safe running time is <60 s.
What is the auxiliary switch rating?
One built-in 1x SPST, 1 A resistive @ DC 30 V auxiliary switch (contacts S1 / S2, NO) for end position indication, interlock control, fan startup.
- Valve Pattern:
- 3-Way
- Valve Size:
- 1/2 Inch
- Connection Type:
- Sweat
- CV Rating:
- 1
- Actuator Type:
- Fail-Safe
- Voltage:
- 24VAC/DC
- Control Signal:
- On/Off
- Auxillary Switch:
- (1) SPST 1A @ 30VDC
