Most remote-control projects are retrofits: the distribution board exists, the circuits exist, the customer wants phone control without replacing the panel or pulling new cables. There are three retrofit routes, and choosing between them is mostly about one question — does the board have a spare DIN module or not?
Route 1: spare DIN space → a DIN-rail smart switch
If the board has one free module width, the cleanest option is a DIN-rail unit that replaces nothing and adds a controlled circuit or sits behind an existing breaker. The AT-SY1 Wi-Fi smart switch is 35 mm, switches up to its rated load and fits exactly one module. The SMR1 metering smart RCBO goes one further and adds overcurrent protection plus energy measurement, which matters when the retrofit is for billing — rental units, holiday homes, shared pumps.
Route 2: no DIN space → hide a mini switch behind the wall plate
When the board is full, the AT-SY3 mini smart switch fits in the wall box behind an existing rocker switch. The manual switch keeps working — the module listens in parallel — so the household keeps its habits and gains app control, schedules and voice control. This is the standard approach in rental properties and renovated buildings where the tenant's habits must not change.
Route 3: the load is outside → a 4G switch on site
For loads beyond the building — garden pumps, signage, shed heaters — rewiring reaches its limit. The AT-SY4 4G smart switch runs on the cellular network and needs no broadband, which makes it the fastest possible deployment: plug in, pair, switch. It is also the route we recommend for temporary installations such as construction sites and market stalls.
Wi-Fi or 4G for a retrofit?
If the board sits inside a building with stable broadband, Wi-Fi units are free to operate and integrate with the household's existing app. If the board is in a basement plant room with poor coverage, a gatehouse, or on a pole at the far end of a farm, a 4G unit is the reliable choice — the comparison in our 4G vs Wi-Fi guide covers the decision in detail. One retrofit trick: a 4G switch inside a metal distribution board usually needs the antenna outside the enclosure; our 4G models accept an external antenna for exactly this reason.
What to check before ordering
- Neutral available at the switch point? Relay modules need a neutral; switch loops without neutral need a DIN-rail unit in the board instead.
- Load current and type — inrush loads (pumps, compressors, LED drivers) need headroom; see the sizing guide.
- Who else needs access? Both Tuya and Mijia ecosystems support multiple users with permission levels — decide who is admin before you hand over.
Send a photo of your distribution board with the door open, plus the list of loads you want to control, and we will propose the exact route and models. Send the photo here.