CHINT NXZ Automatic Transfer Switch, 80-630 A

An automatic transfer switch for dual-supply panels, 80 A to 630 A

The NXZ is CHINT’s PC-class automatic transfer switching equipment (ATSE) for three-phase four-wire duplicate supplies at 400/415 V, 50 Hz, with currents up to 630 A. It moves a load between a normal supply and an alternative supply, mains or generator, so critical circuits in industrial plants, commercial buildings and high-rise buildings keep power through an outage.

Technical specifications

Standard and intelligent controllers

Both controllers monitor the two supplies for phase failure, loss of voltage, undervoltage and overvoltage and switch automatically. The standard A type covers grid-to-grid transfer, while the catalog controller table also lists generator control, fire-control linkage and a communication function, so confirm which of these the intelligent B type carries for your order. Order the controller code in the designation, for example NXZ-125/4A 125A for a 4-pole 125 A switch with the standard controller. If the controller is mounted separately, the connecting wire is ordered on its own.

What to confirm before ordering

Send the load current, the pole count, the neutral arrangement, the controller type and whether the second source is a generator. Pair the switch with correctly rated protection upstream, for example a moulded case breaker from the circuit breakers category such as the Eaton NZMN1-A80, and check the generator start logic with the generator supplier.

Key features of the NXZ series

• PC-class construction: the switch is designed to make and withstand short-circuit currents but not to break them, so it relies on upstream protective devices, which keeps the transfer mechanism simple and robust.
• AC-33B utilization category, covering mixed loads that include motors, resistive loads and up to 30 percent incandescent lighting under infrequent operation.
• Three frame sizes with ratings from 80 A to 630 A in 3-pole or 4-pole form.
• Controller monitors both supplies for phase failure, loss of voltage, undervoltage and overvoltage.
• Transfer and return delays adjustable from 0 to 300 s, allowing a generator to stabilise and avoiding nuisance switching on short dips.
• Choice of integrated controller or separately mounted controller for door or panel-front installation.
• Rated conditional short-circuit current of 100 kA when combined with the appropriate protective device.

How a PC-class transfer switch operates

A PC-class ATSE uses a single motor-driven mechanism to move the contacts between the normal and alternative positions, with a mechanical interlock that prevents both sources from being connected at once. When the controller detects a fault on the normal supply, it waits for the set delay, then transfers the load. If the alternative source is a generator, the controller’s start signal tells the generator to run, and the switch transfers once the generator voltage is available. When the normal supply returns and remains healthy for the return delay, the load is transferred back.

3-pole or 4-pole

The pole count depends on the earthing arrangement. A 4-pole switch transfers the neutral together with the phases, which is commonly needed when the generator neutral is separately earthed or when earth-fault protection must see the correct neutral current. A 3-pole switch is used where the neutral is solidly common to both sources. The system designer should decide this based on the earthing system and local wiring regulations.

Selection guidance

• Choose the rated current at or above the maximum continuous load current, with margin for future growth.
• Coordinate with the upstream breaker or fuse so that the prospective short-circuit current stays within the switch’s conditional rating.
• Check the contact transfer time for loads sensitive to interruption; critical IT loads usually need a UPS in addition to the transfer switch.
• Confirm the controller functions needed, especially generator start, fire-control linkage and communication with a building management system.
• Allow for the dimensions of the chosen frame within the panel, including space for cabling and the controller.

Installation and maintenance

Install the switch vertically on a rigid mounting plate as shown in the manufacturer’s instructions, tighten terminals to the stated torque and use cable lugs of the correct size. Test the transfer sequence before handing over the panel, including simulated loss of the normal supply and return. During routine maintenance, operate the switch through a full cycle, check terminals for heat discolouration and clean dust from the mechanism and controller.

Use in Oman and the GCC

Standby generators are widely installed in hospitals, hotels, telecom sites, water pumping stations, farms and remote industrial facilities across the region, and an automatic transfer switch is a central part of these systems. The standard ambient range of -5 to +40 °C means that panels in hot plant rooms or outdoor enclosures need ventilation or cooling, or the derating guidance in the compensation table must be applied. Dust ingress into panels should be limited with suitable enclosures and filters.

What to include in an RFQ

• Frame and rated current, for example NXZ-250 with 200 A.
• Number of poles and controller type (A standard or B intelligent), integrated or split.
• Source types: grid to grid or grid to generator.
• Required accessories, including the connecting wire for split controllers.
• Quantity, delivery location and whether a complete transfer panel is required.

Documents and quotation

The CHINT NXZ catalog is attached and is the source of the table above. Send the complete designation and quantity through the quotation form for availability from Seven Star LLC.