A manual changeover switch is a mechanically interlocked switch operated by a person; an automatic transfer switch (ATS or ATSE) senses mains failure and moves the load to the generator by itself. Choose manual where an operator is always present and a delay is acceptable; choose automatic where an outage must be covered without intervention — pumps, clinics, telecom rooms, retail and similar sites.
Key facts
- Both exist to prevent mains and generator ever feeding the same circuit at the same time — that interlock is the safety function.
- Transfer equipment is covered by IEC 60947-6-1 (transfer switching equipment).
- Any transfer causes a brief interruption; how long depends on the product and its controller settings, so check the datasheet.
Comparison
| Manual changeover switch | Automatic transfer switch (ATS / ATSE) | |
|---|---|---|
| Operation | A person turns the handle | Controller senses mains failure and transfers automatically |
| Cost and complexity | Lower cost, simple | Higher cost, needs controller settings and commissioning |
| Downtime on mains failure | Until an operator arrives | Short, automatic |
| Best for | Homes, small shops, sites with staff on duty | Pumps, clinics, telecom, retail, unmanned sites |
| CHINT example | NH4-125 (changeover / isolator) | NXZB-63 (ATSE) |
What to specify
- Load current and poles. Choose a rating above the maximum load, and decide between 3-pole and 4-pole (switching the neutral) according to your earthing arrangement.
- Generator capacity and start time. The transfer delay timers should allow the generator to start and stabilise before the load is applied.
- Voltage and frequency thresholds. Set under- and over-voltage and frequency limits that suit your equipment; remember that 60 Hz grids need the right variant.
- Interlock. Never rely on discipline alone: mechanical interlock should make it impossible to close both sources.
- Neutral and earthing. Confirm how the neutral is handled with your generator’s earthing before ordering.
Commissioning checklist
- Check phase rotation of mains and generator before the first transfer.
- Test a transfer under a realistic load, not on an empty board.
- Record the transfer and retransfer delay settings in the handover pack.
- Label both sources and the switch position clearly at the board.
See the SPD, ATSE and isolator range, and tell us your load, voltage and frequency for a quotation. Surge protection for generator-backed sites is covered in SPD Type 1, 2 and 3.
Frequently asked questions
Is an ATS required for a generator?
That depends on local regulations and the application. A transfer arrangement with interlock is always required; whether it must be automatic is set by the project specification.
Can I upgrade a manual changeover to automatic later?
Sometimes, but the switch must be designed for it. It is usually cleaner to specify an ATSE from the start where automatic operation is likely.
Do I need a 4-pole switch?
Where the neutral must be switched or isolated — depending on the earthing system and generator arrangement — a 4-pole device is used. Confirm this with your designer.
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Reviewed by the HAZAM technical team, October 2026. CHINT, DELIXI and TENGEN are trademarks of their respective owners. HAZAM is a first-tier authorised distributor of CHINT products; the authorisation certificate is available on request from our sales manager. Ratings and designations refer to published manufacturer documentation; the certificate for your exact ordering code governs.