Automatic Transfer Switch (ATS) Maintenance Checklist
Make sure standby power transfers when it matters — ATS transfer testing, contact and control checks, timing verification, and generator interface inspection.
What is an ats maintenance checklist?
A automatic transfer switch (ats) maintenance checklist is a structured list of the 10 preventive maintenance tasks — covering visual, functional, safety and record-keeping checks — that keep an automatic transfer switch (ats) running safely and reliably. It groups routine checks by frequency, from daily inspections to annual servicing, so FM teams and building engineers can plan and evidence preventive maintenance.
Core ats checks
- Inspect main power contacts for wear, pitting, and arcing
- Carry out a simulated mains-failure test and confirm transfer to standby
- Verify mechanical interlocks prevent paralleling of sources
- Record transfer test results, timings, and contact condition in the log
What is an automatic transfer switch (ats)?
An automatic transfer switch (ATS) detects a loss of the normal electrical supply and transfers critical loads to a standby source — usually a generator — then transfers back when the mains returns. It is the link that makes standby power automatic, and a failure of the ATS can leave a building without power even when the generator is healthy. Maintenance verifies that the ATS detects supply failure, transfers cleanly within the required time, and transfers back correctly, alongside checking the power contacts, control electronics, connections, and the interface with the generator. It is tested together with the generator as part of a resilient power regime.
This checklist is one of 16 in our electrical maintenance checklists, covering distribution boards, switchgear, generators, UPS, solar PV and EV charging — inspection, testing and thermographic checks.
Typical ATS maintenance checklist
A practical starting point for planned preventive maintenance. Always refer to the manufacturer's O&M manual and site-specific requirements.
Visual Checks
- Inspect main power contacts for wear, pitting, and arcing
- Inspect cable terminations and busbars for tightness and heat
Functional Checks
- Carry out a simulated mains-failure test and confirm transfer to standby
- Confirm re-transfer to mains on supply restoration, with correct timing
- Check the controller, settings, timers, and any display/alarms
- Verify the start signal and interface to the generator operate correctly
- Confirm correct phase rotation and voltage sensing
- Check the enclosure, isolation, and any manual bypass operation
Safety Checks
- Verify mechanical interlocks prevent paralleling of sources
Record Keeping
- Record transfer test results, timings, and contact condition in the log
Download the free ATS maintenance checklist PDF
Get all 10 tasks as a printable PDF — free, no signup needed. Keep a copy in the plant room, attach it to work orders, or share it with your maintenance contractor.
Typical maintenance frequency
Suggested intervals for automatic transfer switch (ats) maintenance. Actual frequencies should follow manufacturer guidance and site-specific risk assessments.
Monthly
- •Transfer test (with generator run)
- •Confirm correct transfer and re-transfer
- •Check controller status
Annually
- •Contact inspection and connection torque check
- •Controller and timing verification
- •Interlock and bypass test
- •Full electrical inspection
Common faults and issues
Issues to be aware of when maintaining automatic transfer switch (ats) equipment.
Safety and compliance notes
Key safety considerations for automatic transfer switch (ats) maintenance. This is general guidance only — always follow OEM instructions, statutory requirements, and your organisation's safe systems of work.
Reference standards and frameworks
- United Kingdom
- BS 7671 (IET Wiring Regulations) and the Electricity at Work Regulations 1989
- North America
- NFPA 70B (electrical equipment maintenance) and ANSI/NETA MTS
Frameworks commonly referenced when planning ats maintenance programmes. Always confirm the requirements that apply to your site and jurisdiction.
Managing ATS documentation with PM Assist
PM Assist helps FM and building operations teams search their O&M manuals and building drawings in seconds. Upload your automatic transfer switch (ats) documentation and ask questions like “When was the last ATS transfer test?” or “What loads does the ATS protect?” — and get source-cited answers instantly.
See PM Assist answer questions about a real ats manual — try the live demo, no signup needed.
Take this checklist with you
Download the branded PDF, generate a custom version for your asset, or run AI search across all your building documentation.
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Further reading on ats maintenance
Frequently asked questions
How often should an ATS be tested?
What happens if the ATS fails?
Can an ATS be operated manually?
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