Frequently Asked Questions

It works with most Mitsubishi units that have an internal CN105 connector: wall-mount, floor, cassette, ducted, and P-series, plus rebranded Trane and American Standard units. Type your model number into the compatibility checker for an instant answer. Mitsubishi Heavy Industries (SRK/SRC/SRF) and Ecodan air-to-water units are not compatible.

The $35 Serin Controller includes the controller and a Mitsubishi CN105-compatible cable, which is everything needed to plug into the indoor unit. An optional wireless remote temperature sensor is available at checkout. You'll also need a USB-C data cable for the one-time firmware flash.

No. The controller arrives without firmware so you pick your platform: flash the free open-source ESPHome or HomeKit-compatible firmware from the browser flash tool in about five minutes.

Use the HomeKit-compatible firmware if your home runs on Apple Home and Siri; use ESPHome if you run Home Assistant. Both are free, both are local, and you can reflash to switch anytime. Full comparison: ESPHome vs HomeKit.

One per indoor head. Each indoor unit has its own CN105 port, so a 3-zone system needs three controllers.

The $35 controller gives you full mode, temperature, fan, and vane control, the same as the $180–$400 MHK2 wall controller or the Kumo Cloud adapter, but locally, with no cloud account and no subscription. See every option compared.

A desktop Chromium browser (Chrome, Edge, or Brave; Safari and Firefox don't support Web Serial) and a USB-C data cable. The flash tool runs entirely in your browser, with nothing to install.

Updates are free and open source, with no subscription, ever. After the first USB flash they arrive over Wi-Fi: ESPHome pushes them from your dashboard, and the HomeKit-compatible firmware updates from its built-in web UI. Details on the support page.

No. Control is local on your network. For control away from home you use your platform's own remote access: an Apple Home hub (Apple TV or HomePod) for HomeKit, or Home Assistant remote access for ESPHome.

Through our Etsy shop. Orders ship from NJ within 1–2 business days, with free US shipping.

Returns and exchanges are accepted within 30 days of delivery, and orders can be cancelled within 12 hours of purchase. Defective units are replaced or refunded in full. The details live on the store policies page.

First check the troubleshooting guide, since most "dead board" reports are a charge-only USB cable. If it's genuinely defective, message the shop on Etsy and we'll replace it or refund you in full, including shipping.