Setup for an automatic transfer switch

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Published on December 8, 2020 5:47:27 AM ● Video Link: https://www.youtube.com/watch?v=kL8WrLPTQf4

Duration: 0:51

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Disclaimer: Improper wiring in these panels can damage devices, create a fire hazard, and provide means to electrocute people. These faults might not appear during initial testing and might only happen under load. The panel shown in this video is intended for portable, short term use and does not serves as a replacement for your main circuit breaker panel. For permanent use, you should install the transfer switch directly in your main breaker panel, and then have it inspected by a certified electrician before using it. Or more ideally, have it installed by the electrician itself.

They're going to cut off power for extended periods during two days. I built this panel as a means to automatically switch between generator power and grid power.

Construction is as follows:

The top left contains a 63 amp breaker for the grid power (Model: TOMZN TOB15-63 WIFI). You can configure when to shut off during over- and undervoltage event and how long to stay off until the switch is re-engaged (provided the voltage has stabilized again). This prevents the system from constantly switching between grid and generator if the grid power fluctuates. You can also set a lower amperage limit than 63, which makes this an adjustable breaker too. It's also Wifi connected, so you can turn the grid power off and on with your smartphone. Connecting to Wifi is optional. The voltage and current cutout can be configured locally with the switches only and not via network.Note that even though this breaker has two poles (for phase and neutral) it is not an RCBO, just a breaker.

The top right is the automatic transfer switch with full isolation, capable of handling up to 100 amps (Model: TOMZN TOQ5-100/2). It switches all connections (including neutral) and not just the phase, preventing any chance of backfeeding into the grid from the generator. This is the single phase version but a three phase (with and without neutral) exists too. The switch in its default configuration prefers grid power whenever available, meaning it only switches to generator if grid power is lost and generator power is available. Switching action is almost instantly and fast enough for your average consumer devices (TV, Computer, etc) to not shut off. A small override switch is available so you can manually turn the red handle to the chosen position, which is useful during generator load testing. This switch has multiple terminals for the grid and generator side. By default you hook them up to their respective 230V phase and neutral to make the switch change the source automatically, but you can also hook them up differently if you prefer a different switching behavior. Each side also has a relay with NO/NC contacts so you can hook up any kind of logic to it, for example to send connected devices into power saving mode if they run on generator. The relay is isolated from mains. A slow acting transfer swtich is available as model TOQ3-63.

The bottom left is the generator input. It consists of a simple switch and a 10 amp breaker. The breaker is technically not necessary since the generator has its own breaker, but I don't trust these flimsy buttons. The power switch can be used to more comfortably hook up the generator. Meaning you can start the generator with the panel plugged in, then after it has warmed up, you can just use the switch instead of having to go outside again and having to plug stuff in.

The bottom right is the output section. It consists of a Swiss outlet (guess the country I'm in) and a 10 amp RCBO. An RCBO is a combination of a fault interrupter (power returns on the ground instead of neutral) and a circuit breaker (device consumes too much power). Circuits in Switzerland are generally already protected by RCD, but the generator is usually not, so it made sense to get this type of switch instead.The grounding is connected between both inputs and the output at all times.Total cost of this was about 200 USD.