The Belimo ZONE315S-35+ZONE24NC-S is a 1/2 in. sweat, 3-way diverting zone valve assembly: the ZONE315S-35 forged brass valve (Cv 3.5, 30 psi close-off) with the ZONE24NC-S normally closed (NC) spring return actuator for AC 24 V, 2-wire on/off control. A built-in SPST auxiliary switch is rated 0.4 A @ AC 24 V.
Built for fan coil units, baseboards and other hydronic applications where fail-safe operation on 2-wire control is required, in systems with variable or constant flow. The compact assembly fits tight spaces where on/off control is needed.
Specifications per Belimo ZONE315S-35 technical data sheet rev 2023-01-10; ZONE315S-35+ZONE24NC-S assembly data sheet rev 2022-01-12. Reviewed 2026-10-09.
Best For
- Fan coil units and baseboard heating
- Hydronic systems with variable or constant flow
- Sweat (solder) 1/2 in. pipe connections
- AC 24 V thermostat or controller circuits switching a 2-wire on/off load
- Signaling valve position to another circuit through the auxiliary switch
Warranty
Belimo covers the valve and the actuator with a 2-year warranty.
Key Features
3-way diverting body
Forged brass body, EPDM seat and housing seal, stainless steel stem; 300 psi body pressure rating.
Cv 3.5, 30 psi close-off
On/off diverting flow with ANSI Class III 0.1% leakage.
Spring return, NC
Spring return AC 24 V actuator for fail-safe operation on 2-wire on/off control.
Built-in auxiliary switch
1 x SPST, 0.4 A resistive (0.4 A inductive) @ AC 24 V; red leads.
Manual override
Hand lever override with integrated mechanical position indication.
cULus listed
CE and cULus listed; meets cULus requirements without an electrical ground connection. NEMA 1 / IP20.
ZOT Supply is an authorized distributor of Belimo products.
Technical Specifications
Valve: Belimo ZONE315S-35
| Valve size | 0.5 in. [DN 15] |
| Flow pattern | 3-way |
| Flow characteristic | On/off, diverting |
| Cv | 3.5 |
| Close-off pressure | 30 psi |
| Body pressure rating | 300 psi |
| Leakage rate | ANSI Class III 0.1% |
| Fluid | Chilled or hot water, up to 50% glycol |
| Fluid temperature range (water) | 32 to 212°F [0 to 100°C] |
| Pipe connection | Sweat |
| Valve body | Forged brass |
| Housing seal | EPDM |
| Stem | Stainless steel |
| Seat | EPDM |
| Suitable actuators | ZONE spring return |
| Valve weight | 0.88 lb [0.40 kg] |
Actuator: Belimo ZONE24NC-S
| Actuator | Belimo ZONE24NC-S spring return, NC |
| Nominal voltage | AC 24 V |
| Nominal voltage frequency | 50/60 Hz |
| Power consumption in operation | 6.5 W |
| Transformer sizing | 7 VA (class 2 power source) |
| Auxiliary switch | 1 x SPST, 0.4 A resistive (0.4 A inductive) @ AC 24 V |
| Electrical connection | 18 in. wire leads |
| Control | On/off, 2-wire |
| Manual override | Hand lever |
| Angle of rotation | 90° |
| Noise level, motor | 35 dB(A) |
| Noise level, fail-safe | 35 dB(A) |
| Position indication | Mechanical, integrated |
| Degree of protection IEC/EN | IP20 |
| Degree of protection NEMA/UL | NEMA 1 |
| Enclosure | UL Enclosure Type 1 |
| Agency listing | CE, cULus |
| Quality standard | ISO 9001 |
| Ambient temperature | 32 to 104°F [0 to 40°C] |
| Storage temperature | -40 to 176°F [-40 to 80°C] |
| Ambient humidity | Max. 95% RH, non-condensing |
| Servicing | Maintenance-free |
| Housing material | Galvanized steel |
| Wiring | Black leads: motor, switched by the thermostat; red leads: auxiliary switch |
Assembled dimensions
| A: actuator length | 4.0 in. [102 mm] |
| B: valve body length, port to port | 2.8 in. [70 mm] |
| C: pipe centerline to top of actuator | 3.5 in. [89 mm] |
| D: overall height | 4.8 in. [122 mm] |
| E / F: pipe centerline to side | 1.2 in. [30 mm] / 1.2 in. [31 mm] |
Documentation
FAQ
What is the Cv and close-off pressure of the Belimo ZONE315S-35+ZONE24NC-S?
Cv 3.5 with a 30 psi close-off pressure. The body pressure rating is 300 psi and the leakage rate is ANSI Class III 0.1%.
What pipe connection does the ZONE315S-35+ZONE24NC-S have?
1/2 in. sweat (solder) ends (DN 15).
What power does the ZONE315S-35+ZONE24NC-S actuator need?
AC 24 V, 50/60 Hz: 6.5 W in operation, transformer sizing 7 VA.
How is the ZONE315S-35+ZONE24NC-S wired?
Two-wire on/off: the thermostat switches power to the two black motor leads. The two red leads connect the auxiliary switch. Leads are 18 in. long.
What is the auxiliary switch rating on the ZONE315S-35+ZONE24NC-S?
1 x SPST, 0.4 A resistive (0.4 A inductive) @ AC 24 V.
What fluids can the ZONE315S-35+ZONE24NC-S control?
Chilled or hot water, up to 50% glycol, from 32 to 212°F [0 to 100°C].
- Valve Pattern:
- 3-Way
- Valve Size:
- 1/2 Inch
- Connection Type:
- Sweat
- CV Rating:
- 3.5
- Max Close-Off Pressure:
- 30 psi
- Max Operating Pressure:
- 300 psi
- Medium Temperature Range:
- 32-212 °F
- Body Material:
- Forged Brass
- Actuator Type:
- Fail-Safe
- Voltage:
- 24VAC
- Control Signal:
- On/Off
- Auxillary Switch:
- (1) SPST 0.4A @ 24VAC
- Power Connection:
- Wire Leads
