930031NT Pressure Differential Bypass Valve
The 930031NT Pressure Differential Bypass Valve is a self-acting hydraulic balancing valve designed to maintain stable pressure equilibrium between supply and return water lines in two-way air conditioning and hydronic HVAC systems. When zone valves close as terminal loads decrease, the valve automatically opens to bypass excess flow, preventing pump overpressure and protecting the entire distribution circuit.
Unlike motorized or electronically controlled balance valves, the 930031NT operates entirely on pressure difference alone, with no external power supply required. The adjustable setpoint covers a pressure difference range of 0.1 bar to 1.0 bar, and the SUS304 stainless steel body ensures long-term durability across working temperatures from 0°C to 110°C at pressures up to 16 bar.
Key Benefits
- No external power required – Operates entirely on the pressure difference between supply and return lines, eliminating electrical dependency and reducing system complexity
- Automatic pressure balancing – Continuously adjusts opening position in response to changes in terminal heat load, maintaining stable differential pressure across all operating conditions
- Wide adjustment range – Setpoint adjustable from 0.1 bar to 1.0 bar via the calibrated scale on the valve body, covering the differential pressure requirements of most two-way AC system designs
- Protects the pump at low load – Ensures a minimum water flow path remains open when terminal loads are minimal or zero, preventing dead-head conditions and pump damage
- High pressure rating – Maximum withstand pressure of 16 bar makes it suitable for high-rise and large-scale commercial HVAC installations
- Wide working temperature range – Rated for 0°C to 110°C, compatible with chilled water, low-temperature hot water, and medium-temperature heating circuits
- SUS304 stainless steel body – Superior corrosion resistance compared to brass-body alternatives, suitable for systems with treated or untreated water
- DN25 (G1″) connection – Standard pipe size for bypass circuits in small to medium commercial HVAC systems
- OEM and ODM customization available – Pressure setpoint range, connection size, and body material can be customized for specific project requirements
Technical Specifications
| Parameter | Specification |
|---|---|
| Model | 930031NT |
| Pressure Difference Adjustment Range | 0.1 bar – 1.0 bar |
| Maximum Withstand Pressure | 16 bar |
| Working Temperature | 0°C – 110°C |
| Valve Kv Value | See differential pressure flow curve chart |
| Valve Body Material | SUS304 Stainless Steel |
| Connection Specifications | DN25 (G1″) |
For Kv values at specific differential pressure setpoints, refer to the differential pressure flow curve chart in the User Manual linked below.
Application & Use Cases
- Two-way valve air conditioning systems – The primary application. As zone valves modulate or close in response to thermostat demand, the bypass valve opens proportionally to maintain stable differential pressure across the pump and distribution circuit
- Fan coil unit systems – Installed on the bypass line connecting supply and return headers in multi-zone fan coil installations to prevent overpressure when multiple zone valves close simultaneously
- Variable flow hydronic heating systems – Used in low-temperature hot water systems with modulating zone valves where differential pressure fluctuates with changing load conditions
- Chiller and heat pump distribution circuits – Protects chiller evaporators and heat pump water circuits from low-flow conditions that can cause freeze damage or operational faults
- Commercial and multi-residential buildings – Suited to medium and large-scale HVAC systems where hydraulic imbalance between zones is a common commissioning and operational challenge
- District cooling and heating connections – Applied at building entry points or riser connections where differential pressure between the district network and building circuit needs regulation
Installation Notes
- Before installation, verify that the pipeline layout is correct and all connections are secure. Confirm that the system pressure rating is consistent with the valve specification
- Flush the pipeline thoroughly before installing the valve to remove debris, weld slag, and pipe scale that could obstruct the valve seat or damage internal components
- Install a ball valve on each side of the pressure differential bypass valve – one on the supply connection and one on the return connection – to allow isolation for inspection and maintenance without draining the system
- Connect both ends directly to the supply and return pipelines without intermediate fittings or restrictions between the valve ports and the main distribution pipes, to ensure the valve senses accurate differential pressure
- Set the pressure difference setpoint using the calibrated scale on the valve body. The scale markings correspond to the ΔP values shown on the differential pressure flow curve chart. Set the value to match the design differential pressure of the system
- The valve should be installed in a position that allows access to the adjustment knob for commissioning and future setpoint changes without requiring pipe disassembly
- Do not install the valve where ambient or fluid temperature may exceed 110°C or fall below 0°C
- After installation, conduct a system pressure test before commissioning to confirm leak-free connections at the valve body and both end fittings
Frequently Asked Questions
What is a pressure differential bypass valve and what problem does it solve?
In a two-way valve HVAC system, zone valves open and close as rooms reach their target temperature. When multiple zone valves close at once, the total flow resistance in the circuit increases sharply. Without a bypass path, the pump operates against this rising pressure, causing noise, vibration, and potentially pump damage. A pressure differential bypass valve opens automatically when differential pressure exceeds the setpoint, diverting excess flow from the supply line back to the return line and holding differential pressure within the design range.
Does the 930031NT require electricity or a control signal to operate?
No. The 930031NT is entirely self-acting. It responds directly to the pressure difference between its two connection ports without requiring any electrical supply, controller, or actuator. This makes it reliable even during power outages and eliminates wiring costs.
How do I set the correct pressure difference setpoint?
The setpoint is adjusted using the knob on top of the valve body. The calibrated scale corresponds to the ΔP values in the differential pressure flow curve chart provided in the User Manual. Set the valve to the design differential pressure of your system, which is typically determined during hydraulic design and commissioning. Refer to the curve chart to understand the flow rate that will bypass at any given setpoint and actual differential pressure.
Why is SUS304 stainless steel used instead of brass?
SUS304 stainless steel offers superior resistance to corrosion, particularly in systems using treated or chemically dosed water. It also performs better in applications with higher temperature ranges and is less susceptible to dezincification, which can be a long-term failure mode in brass valves used with certain water chemistries.
What is the minimum flow the valve maintains when terminal loads drop to zero?
The valve is designed to ensure passage of a minimum water flow through the AC unit even when terminal load is zero. The exact bypass flow at any setpoint and actual differential pressure can be read from the differential pressure flow curve chart in the User Manual.
Can the 930031NT be customized for different connection sizes or pressure ranges?
Yes. Legom offers OEM and ODM customization including pressure difference adjustment range, connection size, and valve body material. Contact our team to discuss your project requirements.
OEM & ODM Customization
Legom supports full OEM and ODM services for the 930031NT Pressure Differential Bypass Valve. Our engineering team can customize pressure setpoint range, connection size, and body material to match your system design and product requirements. All customization projects are handled with strict confidentiality. Contact us via WhatsApp or info@legomsmart.com.
User Manual
Product information last reviewed by the Legom Technical Team. For the most current specifications, refer to the official datasheet or contact our sales team.
Custom OEM & ODM Solutions
Legom is a direct manufacturer offering end-to-end OEM and ODM services. With our in-house engineering and production capabilities, we work closely with distributors and system integrators to deliver fully customized solutions under strict NDA.
