Automatic transfer switch: how to size, choose, and install

Automatic Transfer Switch Buying Guide: How to Choose the Right ATS, Remote Start, Generator Plugs, and Cover

An automatic transfer switch (ATS) is the brain of a backup power system. It detects a power outage, starts the generator, and safely switches your home or business from the grid to generator power. When mains power returns, it switches back and cools the generator down.

If you are setting up backup power in Australia, you will likely need an auto generator transfer switch or a manual generator transfer switch, matching generator plugs and cord sets, a compliant inlet box, the right accessories for a remote start generator or generator remote start kit, and a weather-rated generator cover.

Use cases range from small homes in regional NSW and QLD, to cafés and clinics in suburban VIC, to sheds on WA stations. It also helps where uptime matters, like refrigeration, pumps, servers, or a sensitive suspension test rig in a workshop.

What Is an Automatic Transfer Switch (ATS) and How It Works

An ATS watches the voltage on your utility feed. When it senses a failure, the ATS sends a start signal to the generator. After the generator stabilises, the switch transfers the load. When utility power is stable again, the ATS re-transfers and signals the generator to cool down and stop. This all happens without you touching a thing.

ATS operation cycle (simple steps)

• Sensing: Monitors the mains. If voltage drops or fails, it begins the start sequence.

• Transfer: A safe, break-before-make changeover isolates the grid and connects the generator. This prevents backfeed into the network.

• Re-transfer: When mains voltage is stable for a set time, the ATS moves the load back and shuts down the generator after cooldown.

Common configurations include whole-building (service-entrance) ATS that feeds everything in the site, or selected-circuit ATS that feeds only key circuits. Residential sites are usually single-phase 230/240 V. Commercial sites may be three-phase 400/415 V (or 208/480 V in some imported plant). For Australian installs, ensure equipment selection and wiring comply with AS/NZS 3010 for generating sets and local DNSP rules. Generators should be rated and tested to ISO 8528 for performance and endurance.

You can compare whole-home versus selected-circuit setups to see what fits your budget and risk profile.

(References: (source) (source) (source))

ATS vs Manual Generator Transfer Switch vs Interlock

Not all transfer switch generator options are the same. Here is how they differ in plain terms.

• Automatic transfer switch (ATS): Fully automatic. Starts the generator and switches power without manual work. Best for critical loads, remote sites, elderly users, and places that must stay on.

• Manual generator transfer switch: You flip it yourself during an outage. Lower cost. Good for portable generators and selected circuits.

• Interlock kit: A panel add-on that prevents the main and generator breaker from being on at the same time. Manual operation. Budget option. Rarely suitable for whole-building service.

All three aim to isolate the grid from the generator. This isolation is vital for safety and legal compliance. In Australia, ensure isolation and changeover wiring complies with AS/NZS 3010 and your local authority. For imported or US-focused references, NEC Article 702 and UL 1008 show the intent behind safe standby systems and transfer equipment.

(References: (source) (source))

Compliance and Safety Must-Knows for an Automatic Transfer Switch

Safety comes first. A generator transfer switch is not just convenient; it is a control and protection device that prevents backfeed and shock risks. In the US context, NEC Article 702 requires code-compliant transfer equipment for standby systems, and UL 1008 is the benchmark listing for transfer switches. For Australia, use this as general guidance and also follow AS/NZS 3010 and state rules from your DNSP and local AHJ (Authority Having Jurisdiction).

• Use listed transfer switches. In US documents, look for UL 1008. Locally, buy reputable brands and verify conformity to AS/NZS requirements and manufacturer instructions.

• Service-entrance-rated ATS for whole-building installs. These include the main disconnect and correct neutral handling.

• Backfeeding the grid is illegal and dangerous without approved transfer equipment. Never do it.

• Permits, inspections, and licensed electricians are strongly recommended (and often required). This reduces risk and ensures fit-for-purpose work.

Note: Australian homes often have single-phase 63–100 A mains. Many US guides talk about 200 A. The principle is the same: match ATS rating to the main service size and follow local standards and inspection processes.

(References: (source) (source))

How to Choose the Right Automatic Transfer Switch (step-by-step buyer's guide)

1) Match service size

• Service-entrance installs: The ATS amperage should match the main breaker rating. For example, a 200 A panel uses a 200 A ATS. In Australia, if your main is 63 A single-phase, select a 63 A (or appropriately rated) ATS.

2) Check generator compatibility

• Identify generator type: portable or standby.

• Confirm voltage and phase: single-phase 230/240 V or three-phase 400/415 V locally (208/480 V on some imported plant).

• Verify start signal compatibility: two-wire start, dry contacts, or proprietary control interface.

3) Do a load calculation

• List essential loads: fridge/freezer, lights, router, water pump, medical equipment, security, or servers.

• Consider motor starting current (LRA/inrush) for pumps and AC compressors; allow headroom.

• If available, use load management modules to shed non-essential loads during startup.

• Choose an ATS with suitable withstand/closing ratings (kAIC) for the site fault level.

4) Poles and neutral

• Single-phase 230/240 V: Typically 2-pole. The neutral may be solidly connected or switched, based on system bonding and AS/NZS 3010 requirements.

• Three-phase sites: 3- or 4-pole. Switched neutral is often needed if the generator is a separately derived source.

5) Enclosure rating

• Indoor (clean, dry): NEMA 1 (or equivalent local IP rating).

• Outdoor/exposed: NEMA 3R/4 (consider UV, dust, and rain). For coastal sites, corrosion resistance is important.

6) Features that help

• Load management: prioritise AC, pumps, ovens.

• Exercise timer: keeps the generator healthy with routine run tests.

• Connectivity: Wi‑Fi/app monitoring where supported.

• Service-entrance rating: includes main disconnect and neutral management.

• Quiet transfer: soft transfer strategies for sensitive electronics.

7) Cross-check accessories

• Match the inlet box and cord set to the ATS rating and generator plugs type.

• Plan for a weather-rated generator cover for storage or running (if designed for operation).

• Check you have a remote start generator capability or add a compatible generator remote start kit.

(References: (source) (source) (source))

Sizing and Selection Examples for a Generator Transfer Switch

Example 1: Whole-home, 200 A service

• Choose a 200 A service-entrance-rated ATS to match the main breaker.

• Ensure the generator’s kW matches your essential loads and its fault withstand is adequate.

• Verify transfer switch listing (e.g., UL 1008 in US documents) and compliance with AS/NZS 3010 for local installation practice.

• Coordinate the correct generator plugs, inlet box, and cable set if using a portable generator as a temporary backup source during long outages.

Example 2: Selected-circuit setup with a portable generator

• Use a 6–10 circuit manual generator transfer switch or a small ATS feeding a sub-board with essentials (fridge, lighting, NBN router, pump).

• Match inlet type (e.g., NEMA L14-30 or 14-50) and cable gauge to the ATS and generator output.

• Consider load management for heavy appliances (hot water, AC) to prevent overload.

Example 3: Small commercial three-phase site

• For a café, clinic, or workshop with 3φ 400/415 V, select a three-phase ATS (3- or 4-pole). Switched neutral may be required where the generator is a separately derived source.

• Use an outdoor-rated enclosure (NEMA 3R/4 or local equivalent) if mounted outside, with attention to dust, heat, and spray.

• Verify control interface compatibility and test transfer under load before handover.

Australian context examples:

• Rural NSW home with a bore pump: Single-phase 63 A service, selected circuits on a 63 A ATS, allow for high inrush on the pump.

• QLD cyclone belt: Three-phase small business with refrigeration; choose a 3φ ATS, outdoor-rated cabinet, and load shedding to prioritise fridges.

• SA bushfire-prone area: Whole-home ATS with safe generator location, ember-resistant enclosure, and routine monthly exercise per ISO 8528 guidance on operational readiness.

(References: (source) (source) (source))

Installation Overview for a Transfer Switch Generator and Generator Plugs

Who should install

• Service-entrance ATS units should be installed by a licensed electrician. Permits and inspections are often required. This protects you, ensures compliance with AS/NZS 3010, and maintains warranties.

Site prep checklist

• Panel and service location confirmed with working clearances.

• Cable path and conduit plan for ATS and inlet box.

• Grounding and bonding checked per AS/NZS 3010 and OEM manuals.

• Inlet box sited for safe generator placement (exhaust away from windows and doors), weather and UV exposure considered.

• Correct generator plugs, matching inlet, and cable gauge verified.

Commissioning checklist

• Simulate an outage: verify start, transfer, re-transfer, and cooldown sequences.

• Neutral and earthing verified; RCDs and protective devices tested.

• Exercise timer set; load management modules configured.

Common pitfalls

• Undersizing the ATS relative to main service.

• Incorrect neutral bonding or missing switched neutral where required.

• Mismatched generator plugs/cords or inlet rating.

• Improper inlet box placement leading to CO risk or water ingress.

• Skipping inspection and documentation.

Safety note: Never backfeed via “suicide cords” (male-to-male). Always use listed transfer equipment that safely isolates the grid.

(References: (source) (source))

Remote Start Solutions: Remote Start Generator and Generator Remote Start Kit with an Automatic Transfer Switch

Many standby systems already support auto start via the ATS. For portable units, a generator remote start kit can add push-button, wireless, or app-based starting. This is helpful for older users, remote sheds, or stormy nights when you want to stay indoors.

Compatibility checks

• Electric start present (battery, starter solenoid, charging circuit).

• Kit wiring diagram matches your model and does not conflict with ATS start contacts.

• Warranty position confirmed with the manufacturer.

Feature options

• Wired vs wireless remotes; check range for larger blocks or farms.

• Weatherproof modules for outdoor mounting.

• Low-battery alerts, status LEDs, and safety interlocks.

Integration tip

• Coordinate the ATS’s start/stop dry contacts with the kit controller so only one device commands the starter at a time. Use cranking lockout where available.

Generator Plugs, Cords, and Inlet Boxes for a Transfer Switch Generator

Choosing the right interface keeps voltage and current within ratings and ensures a safe connection during an outage.

Common plug types

• NEMA L14-30: 30 A, 120/240 V, twist-lock. Common for mid-size portables.

• NEMA 14-50: 50 A, 120/240 V, straight-blade. Suits higher-output portable generators or EV-style cords.

• NEMA TT-30: 30 A, 120 V. Typical in RV applications.

• NEMA L5-30: 30 A, 120 V, twist-lock. Single-voltage gear.

Although NEMA patterns are US-based, many generators and inlets sold in Australia use these references. Always confirm your receptacle and inlet markings, voltage, and current ratings.

Selection rules

• Match the plug/receptacle type on the generator and the inlet box.

• Size cable gauge for current and length; use outdoor-rated cords.

• Use RCD/GFCI protection where required by site conditions.

Inlet boxes

• Size the inlet amperage to the ATS input and generator output.

• Weather rating must suit the location (rain, dust, UV).

• Label the inlet clearly with voltage, phase, and amperage.

Adapters

• Use only listed/approved adapters. Some adapters may not be code-compliant; check with your electrician and local AHJ before use.

Protecting Your Investment with a Generator Cover

A generator cover protects against dust, rain, and sun. It can extend equipment life and keep things ready for the next outage.

Storage covers

• Breathable, water-resistant fabrics keep moisture at bay while avoiding condensation.

• UV resistance for harsh Australian sun. Look for seam-sealed stitching.

Running covers/tents

• Use only covers designed for operation. They allow correct exhaust path and airflow.

• Never run a generator under a sealed tarp or indoors. Carbon monoxide is deadly.

Fit and durability

• Choose the right size and tie-downs to prevent wind damage.

• Cold-weather kits may be needed in alpine regions to keep the engine warm for reliable starting.

Quick Buyer Checklists: Automatic Transfer Switch, Generator Plugs, Generator Cover, Remote Start Generator

ATS checklist

• Service size (A) matches main breaker (e.g., 63 A, 80 A, 100 A, 200 A).

• Service-entrance rated if feeding the whole site.

• Phase/voltage match; poles and neutral switching as required by AS/NZS 3010.

• Withstand/closing ratings appropriate for fault level.

• Enclosure rating for indoor/outdoor use.

• Load management, exercise timer, and monitoring as needed.

• Plan for permits, inspection, and licensed installation.

Remote start checklist

• Electric start present and battery healthy.

• Kit compatibility and wiring diagrams verified.

• Integration with ATS start contacts sorted.

• Range, weatherproofing, and alerts picked for your site.

• OEM warranty position confirmed.

Plugs/cords checklist

• Correct plug type (e.g., L14-30, 14-50) and amperage.

• Cable gauge and length suited to load and run.

• Outdoor rating and RCD/GFCI as needed.

• Inlet box voltage/phase/amp match and weather rating.

Cover checklist

• Storage vs running type selected.

• Fit and tie-downs correct for your model.

• UV resistance and water resistance for Aussie conditions.

• Ventilation for safe operation (running covers only).

FAQs: Automatic Transfer Switch, Generator Transfer Switch, Generator Remote Start Kit, Generator Plugs, Generator Cover

Do I need an ATS or a manual generator transfer switch?

Use an ATS for hands-off backup and critical loads. Manual switches cost less but need you to operate them during an outage. (References: (source) (source))

What size ATS for 200 A service?

Pick a 200 A ATS to match a 200 A main breaker. In Australia, match your actual main size (e.g., 63 A, 80 A, 100 A) the same way. (References: (source) (source))

Can I install an ATS myself?

It is strongly recommended to use a licensed electrician. Permits and inspections may apply. This ensures compliance with AS/NZS 3010 and manufacturer instructions. (Reference: (source))

Will a generator remote start kit void my warranty?

It can if it is incompatible or not installed per the maker’s guide. Confirm with your OEM before fitting.

Which plugs do I need for my ATS?

Match the NEMA/receptacle type on your generator and the inlet box rating (e.g., L14-30, 14-50). Check voltage, phase, and amperage.

Can I use a generator cover while running?

Only if the cover is designed for operation with proper ventilation. Never run under a storage-only cover or in an enclosed space.

Product Bundles and Next Steps: Automatic Transfer Switch, Generator Plugs, Generator Cover, Remote Start Generator, Generator Remote Start Kit

Many buyers pair an ATS with a matched inlet box, the correct generator plugs and cords, and a weather-ready generator cover. Where convenience matters, a remote start generator or a compatible generator remote start kit can streamline use. For a neat setup in Australia, confirm AS/NZS 3010 compliance, suitable IP/NEMA enclosure ratings for your location, and that your generator performance aligns with ISO 8528 ratings. Keep records of test runs and exercises so you know the system works when storms or bushfires hit.

Written by an electrical installer with extensive ATS commissioning experience across residential and commercial sites in QLD, NSW, VIC, SA, WA, TAS, NT, and the ACT. Electrical work should always be performed by qualified professionals under local rules.

FAQ

• What does an automatic transfer switch do? It detects a power outage, starts the generator, switches your load to generator power, and then switches back when mains returns.

• Is a manual generator transfer switch safe? Yes, when properly installed. It isolates the grid and the generator, but you must operate it by hand during an outage.

• How do I size an ATS? Match the ATS amperage to your main breaker (e.g., 63 A, 100 A, 200 A). Confirm phase/voltage and neutral switching needs.

• Do I need a generator remote start kit? If your generator does not support auto start, a compatible kit adds push-button or wireless control. Check warranty and wiring first.

• Which generator plugs are common? L14-30 and 14-50 are common for 120/240 V portables. Always match the inlet box and cable gauge to the current.

• Can I run a generator under a cover? Only with a running-rated cover/tent that allows safe exhaust and airflow. Never use a storage cover while running.