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When to replace the relay with a contactor: LED inrush current
Ten 5 W downlights are 0.2 A in steady state and tens of amps at switch-on. Why the relay welds months later, and how to fix it properly.
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How to install an RC snubber, step by step
Where the snubber goes and why distance to the motor decides everything, plus the wiring mistake that trades one fault for another.
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How to install a bypass, step by step
Exactly where the bypass goes, why it belongs in the light fitting rather than the switch box, and how to confirm it worked.
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The Shelly restarts when a motor switches off: the inductive spike
You have a Shelly controlling an extractor fan. Every time you switch it off, the device restarts: it vanishes from the app for a few seconds and comes back. Or you start hearing a sharp click from the relay that was not there at first. This is not a defect in the device or a…
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LED bulb glowing or flickering: what a bypass fixes
You fit the device behind the switch, everything looks right, and when you turn the light off the bulb keeps a faint glow. Or worse: it flickers every few seconds, as though it were breathing. You have done nothing wrong. It is a predictable consequence of combining a no-neutral device with modern LED bulbs, and…
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Automating roller blinds: cover profile and calibration, step by step
A two-channel module turns any conventional blind motor into one you can drive from a phone. But there is a difference between “the outputs raise and lower the blind” and “the blind knows where it is”, and that difference comes down to two steps many people skip. Before starting Switch off the power and verify…
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Automating a two-way circuit: the setting that solves it
A light controlled from two points is a two-way circuit; from three or more, there is an intermediate switch in the middle as well. They are among the most common arrangements in any home, and also where most people get stuck when automating: the setup works, but the physical switch stops behaving as it should.…
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How to install the Shelly Pro 3EM-3CT63, step by step
The Shelly Pro 3EM-3CT63 shares its chassis and electronics with the Pro 3EM, but changes the way it measures entirely. Instead of three split clamps it uses the 3CT63: a single piece that takes all three phases and sits directly on the breaker. It is the meter for boards where nothing else will fit. Two…
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How to install the Shelly Pro 3EM, step by step
The Shelly Pro 3EM is the reference three-phase meter of the range: up to 120 A per phase, DIN rail mounting, and the only meter in the family compatible with Matter. Fitting it has more edges than a single-phase meter, and nearly all of them gather at one point: which clamp goes on which phase.…
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How to install the Shelly Pro EM-50, step by step
The Shelly Pro EM-50 is a single-phase, two-channel DIN rail energy meter, and it has one feature that sets it apart from the rest of the Pro range: it has a built-in relay. That saves a module for anyone who wants to measure and drive a contactor. Before opening the board Switch off at the…