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.
Also available as editable Excel and Word — with asset, sign-off and findings columns.
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 17 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.
The PDF is free and needs nothing. The Excel and Word versions add asset details, sign-off and findings columns so you can record the work as you do it — we ask for an email address for those.
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.
The checklist tells you what to check. The manual tells you the numbers.
Ask a ats manual a question and get the answer back with the page it came from. No signup, and you can drop in your own PDF instead of the sample.
“When was the last ATS transfer test?”Runs against a sample chiller manual so you can see the shape of the answer — then try it on one of yours.
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.
Related free tools
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Distribution Board maintenance checklist
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Battery Energy Storage System (BESS) maintenance checklist
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Further reading on ats maintenance
Compliance & CAFM
Run automatic transfer switch maintenance in PM Assist
This checklist is also a planned maintenance programme in PM Assist, included in every paid plan alongside the compliance register and mobile inspections.
- Add an automatic transfer switch to a building's asset register and this maintenance programme is created for you, with each task on its frequency in the planner.
- Standby Generator Service & Load Test and HV Switchgear Maintenance are tracked on the compliance register, with the date last done, the date next due and the certificate.
- Contractors can be given a login to see their jobs and upload certificates.
Frequently asked questions
How often should an ATS be tested?
What happens if the ATS fails?
Can an ATS be operated manually?
Manage your building documentation with AI
PM Assist gives FM teams instant access to O&M manuals, drawings, and maintenance knowledge — all searchable with AI.
- Upload and organise building documentation
- AI-powered search across all your manuals
- Source-cited answers for maintenance queries
- Team collaboration and access control
- No credit card required to start