The Belimo ZONE315N-35+ZONE120NC-S is a 1/2 in. NPT, 3-way diverting zone valve assembly: the ZONE315N-35 forged brass valve (Cv 3.5, 30 psi close-off) with the ZONE120NC-S normally closed (NC) spring return actuator for AC 120 V, 2-wire on/off control. A built-in SPST auxiliary switch is rated 5 A @ AC 120 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 ZONE315N-35 technical data sheet rev 2023-01-10; ZONE315N-35+ZONE120NC-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
- Threaded 1/2 in. piping (female NPT ends)
- AC 120 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 120 V actuator for fail-safe operation on 2-wire on/off control.
Built-in auxiliary switch
1 x SPST, 5 A resistive (5 A inductive) @ AC 120 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 ZONE315N-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 | NPT female ends |
| Valve body | Forged brass |
| Housing seal | EPDM |
| Stem | Stainless steel |
| Seat | EPDM |
| Suitable actuators | ZONE spring return |
| Valve weight | 1.1 lb [0.50 kg] |
Actuator: Belimo ZONE120NC-S
| Actuator | Belimo ZONE120NC-S spring return, NC |
| Nominal voltage | AC 120 V |
| Nominal voltage frequency | 50/60 Hz |
| Power consumption in operation | 6.5 W |
| Transformer sizing | 7 VA |
| Auxiliary switch | 1 x SPST, 5 A resistive (5 A inductive) @ AC 120 V |
| Electrical connection | 6 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 ZONE315N-35+ZONE120NC-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 ZONE315N-35+ZONE120NC-S have?
1/2 in. female NPT ends (DN 15).
What power does the ZONE315N-35+ZONE120NC-S actuator need?
AC 120 V, 50/60 Hz: 6.5 W in operation, transformer sizing 7 VA.
How is the ZONE315N-35+ZONE120NC-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 6 in. long.
What is the auxiliary switch rating on the ZONE315N-35+ZONE120NC-S?
1 x SPST, 5 A resistive (5 A inductive) @ AC 120 V.
What fluids can the ZONE315N-35+ZONE120NC-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:
- NPT
- CV Rating:
- 3.5
- Actuator Type:
- Fail-Safe
- Voltage:
- 120VAC
- Control Signal:
- On/Off
- Auxillary Switch:
- (1) SPST 5A @120V
