Changeover Switch or ATS Panel? Choosing the Right Option for Grid and Generator Supply

Almost every building in Nigeria needs to switch between grid supply and a generator. The device that does this, a changeover switch or an automatic transfer switch (ATS), is one of the most important parts of the installation. Get it wrong and you risk damaged equipment, a back-feed into the DisCo network, or a generator that never takes the load when it should.

What a changeover does

A changeover connects your building’s load to one supply at a time: grid or generator, never both. It must break all live conductors of one supply before connecting the other, so the two sources can never be connected together.

Manual changeover switch

Someone physically moves a handle from grid to generator after starting the generator, and back again when grid supply returns.

• Good for: homes, small shops and small offices where someone is always present.
• Advantages: low cost, simple and easy to maintain.
• Disadvantages: power stays off until someone acts, and it relies on people following the right sequence.

Automatic transfer switch (ATS) panel

An ATS monitors the grid supply. When it fails, the controller starts the generator, waits for it to stabilise, then transfers the load. When grid supply returns and stays stable, it transfers back and runs the generator down to cool before stopping it.

• Good for: offices, hospitals, banks, hotels, factories and estates, anywhere downtime is costly or nobody is on hand.
• Advantages: fast, consistent switching with no human error; can monitor voltage and phase loss; can start and stop the generator.
• Disadvantages: higher cost, and it needs correct setup and periodic testing.

Sizing it correctly

Whichever type you choose, it must be rated for the full current of the supply it switches, with suitable breaking capacity. For three-phase supplies, the changeover must switch all phases, and the neutral arrangement must suit how your system is earthed. An undersized changeover overheats at its contacts, one of the most common causes of burnt panels we see.

Common changeover mistakes we fix

• Changeover rated lower than the main breaker or generator output
• Grid and generator able to connect together, risking back-feed and generator damage
• Neutral not switched or not arranged correctly for the earthing system
• Loose, undersized cable terminations at the changeover
• ATS timers set so short that it switches on every brief voltage dip
• No phase-failure monitoring, so the building runs on two phases after a grid fault

Which should you choose?

If someone is always present and short outages are acceptable, a correctly rated manual changeover is fine. If outages cost money, affect safety, or happen when nobody is there, choose an ATS panel. For larger sites with several generators, a synchronisation panel lets generators share the load.

Getting the size right starts with a load assessment.

Talk to Corustar

Corustar Technological Services is an electrical engineering contractor based in Ikeja, Lagos, working across Nigeria. See our LV Panel Assembly service, request a quote, or call +234 816 976 9672. For outages and faults, call our 24/7 emergency line on 0705 739 9297.