A transfer switch does one job: move a load between the normal utility source and a standby source without ever connecting the two together. That last part is the whole reason the device exists.
The choice between automatic and manual isn’t about quality. It’s about who does the transferring, and how long the load can sit dead while it happens.
Automatic transfer switch (ATS)
An ATS monitors the normal source continuously. When it detects a loss or an out-of-tolerance condition, it signals the generator to start, waits for the standby source to stabilise, and transfers the load — with no one present. When utility power returns and holds, it transfers back and signals the generator to shut down after a cooldown period.
Choose an ATS when:
- The building is unoccupied at times when an outage could occur
- The load cannot tolerate the delay of someone walking to the switch
- Life-safety, egress lighting, fire alarm, or elevator recall is involved
- The site is remote or unstaffed
- Code or the authority having jurisdiction requires automatic transfer for the load class
Manual transfer switch (MTS)
An MTS requires an operator. Someone starts the generator, walks to the switch, and moves it from normal to standby. On restoration, someone moves it back.
That sounds like a limitation, and for some loads it is. But an MTS is simpler, has fewer components to fail, costs less, and gives a human explicit control over when transfer happens — which is occasionally what you want.
Choose an MTS when:
- The site is staffed when it matters
- The load can tolerate a manual response
- Budget matters more than transfer speed
- You want deliberate control over when the generator picks up load
The question that actually decides it
Not “which is better” — ask instead: how long can this load be dead, and will someone be there?
If the answer is “a few minutes is fine and there’s always someone on site,” an MTS is honest engineering, not a compromise. If the answer is “the load cannot drop” or “the building may be empty at 2am,” you need an ATS and the cost difference isn’t really a decision. Life-safety loads generally take that decision out of your hands.
What to specify once you’ve chosen
- Amperage — sized to the load being transferred, not the service
- Poles — 3-pole, or 4-pole where the neutral must be switched. Which one depends on your grounding and bonding arrangement; confirm with the design engineer.
- Enclosure — NEMA 1 indoor, NEMA 3R for outdoor
- Voltage and phase — matched to both sources
Nav-Tech enclosed transfer switches
We build both automatic and manual transfer switches in 100A and 200A, 3-pole, in outdoor NEMA 3R hinge-cover cabinets with a gray powder-coat finish. Other amperages and configurations are available on request.
Automatic transfer switches → · Manual transfer switches →
Specifications are subject to change without notice. Consult your serving utility and the authority having jurisdiction before ordering or installing. All installations must be performed by a licensed electrician in accordance with applicable codes.