Automatic Transfer Switches

AUTOMATIC TRANSFER SWITCHES

Automatic Transfer Switches (ATS) for Generators

Keep your building powered automatically when the mains fails. Freeman Energy supplies and installs automatic transfer switches (ATS) for standby generators across the UK — helping businesses, farms, commercial units and industrial sites maintain continuity.

Automatic changeover Safe mains / generator interlock Faster restoration Professional commissioning

Request a Quote Generator Sizing Guide Single Phase vs Three Phase

What is an Automatic Transfer Switch?

An Automatic Transfer Switch (ATS) is a changeover device that monitors the incoming utility supply. If the mains power fails or drops outside acceptable limits, the ATS signals the generator to start and then transfers the load to generator power. When the mains returns and stabilises, it transfers back and the generator shuts down.

The result: minimal downtime, reduced risk to critical equipment, and a safer, compliant changeover compared to manual switching.

Detect
ATS senses loss/poor quality of mains voltage.

Start
Generator starts and reaches stable voltage & frequency.

Transfer
Load changes over to generator supply (interlocked).

Return
On mains recovery, ATS transfers back and stops the generator.

Good to know: changeover settings (delays, warm-up, cool-down) are configured during commissioning to suit your site, especially where short utility “blips” are common.

Why Use an ATS?

Continuity: keeps lights, heating, security, servers and production equipment running.
Protection: prevents unsafe back-feeding into the grid when installed correctly.
Speed: restores power in seconds to minutes, depending on generator start time.
Confidence: consistent changeover sequence, less reliance on staff being on site.

Choosing the Right ATS (What We Size & Specify)

ATS systems are not one-size-fits-all. Freeman Energy will size and specify your switchgear based on:

Supply type: single-phase or three-phase (and neutral/earthing arrangement).
Load profile: total running kW/kVA, motor starting currents and sensitive electronics.
Changeover rating: continuous current (A) and short-circuit/withstand capability.
Control interface: compatibility with your generator controller (2-wire start, dry contacts, etc.).
Installation environment: indoor/outdoor enclosure, IP rating and cable entry.
Future headroom: allowance for additional load and site expansion.

ATS Installation & Commissioning

A professional install is essential for safety and reliability. Our typical process includes site assessment, switchgear selection, cabling and terminations, control wiring to the generator, functional testing and commissioning.

We also provide practical advice on generator location, ventilation, fuel arrangements and load priorities so your backup system performs as expected.

ATS Quick Guide

Use this checklist to speed up quoting. If you don’t know an answer, no problem — we’ll confirm during a survey.

Mains: Single-phase / Three-phase
Generator: standby rating (kVA) & controller type
Load: total kW/kVA + biggest motor/compressor
Priority loads: what must stay on during an outage
Location: switchgear position & cable route

Safety

Interlocked changeover helps prevent back-feeding.

Reliability

Correct delays and testing reduce nuisance transfers.

Compliance

Installed and commissioned to the correct standards.

FAQ

How quickly will power come back on?

Most standby generators restore power within seconds to a couple of minutes. The exact time depends on start sequence, warm-up settings and the ATS transfer delay used to avoid reacting to brief mains dips.

Can an ATS run only “critical” circuits?

Yes. Many sites use an essential loads distribution board or load-shedding strategy so the generator powers critical equipment only (e.g., pumps, security, refrigeration, IT) rather than the entire building.

Do I need a manual bypass?

A bypass/isolation arrangement can be useful for maintenance and testing, especially on critical sites. We’ll recommend the best option based on your downtime tolerance and operational needs.

Will an ATS work with any generator?

Most modern standby generators support ATS control via dry contacts or 2-wire start. Compatibility depends on the generator controller and the required signals/feedback. We verify this during specification.

Tip: If your site has large motors (compressors, pumps, workshop machinery), allow for starting currents. This affects both generator and ATS sizing.