Shower Fan Automation
Humidity-spike detection that runs your bathroom fan for you — no more mould, no more forgetting.
From $249 NZD Includes preconfigured Shelly 1 Gen3 + BLU H&T, tested — final price TBC at enquiry
Questions? info@calibrate.nz — Christchurch NZ
Works standalone • Expands to Home Assistant
Click image to enlarge — use arrows or thumbnails to browse
Problem
The annoying problem
Bathrooms stay damp after showers. Manual fans get left on (wasting power) or left off (growing mould). Landlords and homeowners need reliable moisture control without rewiring or constant attention.
Solution
Shower Fan Automation
Humidity-spike detection that runs your bathroom fan for you — no more mould, no more forgetting.
Shelly is the platform — this climate solution is the product.
How it works
How it works — stepped
BLU H&T monitors humidity every few seconds. A Shelly 1 Gen3 script watches for a rapid humidity spike (>2% rise within 90s) — the signature of a shower starting. Fan switches on automatically and runs for 15 minutes after the spike, extending if humidity keeps rising. No cloud dependency, local execution.
Technology: local Shelly script — standalone; Home Assistant / Hub optional
- 1
Step 1
BLU H&T samples humidity continuously (BLE, every few seconds)
- 2
Step 2
Script detects 2% rise within 90s rolling window — shower signature
- 3
Step 3
Fan switches ON immediately via Shelly 1 Gen3 relay
- 4
Step 4
15-min overrun auto-extends if humidity keeps rising, then switches OFF
Hardware
Hardware included
Everything that ships in the system — no hunting for parts.
-
×1
Shelly 1 Gen3
Wi-Fi relay, runs spike-detection script locally
-
×1
Shelly BLU H&T (BLU H&T)
Bluetooth humidity & temperature sensor
Preconfigured
What's preconfigured
We do the boring config so you don't have to. You install. Test happens before shipping.
- ✓ Shelly script flashed & configured (spike detection + 15-min overrun)
- ✓ BLU H&T paired and calibrated to Shelly 1 Gen3
- ✓ Thresholds tuned: 2% rise / 90s window / 15-min overrun
- ✓ Bench tested on 192.168.1.x before shipping
In the box
What's in the box
- • Shelly 1 Gen3 ×1 (preconfigured)
- • Shelly BLU H&T ×1 (pre-paired)
- • Wiring diagram (electrician-friendly)
- • Install notes + threshold tuning guide
- • Test report — TBC (placeholder)
Installation
Installation
Clear separation: what you do vs what your electrician does.
You — DIY
Sensor placement, Wi-Fi, app-free defaults.
- • Existing bathroom fan with accessible wiring
- • 2.4 GHz Wi-Fi coverage in bathroom
- • BLU H&T placed away from direct steam jet
Electrician — 240V
Mains wiring for Shelly 1 Gen3. We provide diagram.
- • Electrician required for Shelly 1 Gen3 install (240V)
Technical details
- power
- 240V AC via Shelly 1 Gen3
- connectivity
- Wi-Fi + Bluetooth LE
- compatibility
- Any 240V extractor fan
- warranty
- Supplier warranty — TBC
Why this solution
Why this solution vs buying devices
Same Shelly parts — but you skip the pairing, scripting and tuning.
| Feature | Buying devices | With this solution |
|---|---|---|
| Pairing & calibration | You pair BLE, debug thresholds | Pre-paired, calibrated, tested |
| Automation logic | You write/flash Shelly script | Script flashed — 2% / 90s / 15 min tuned |
| Install docs | Generic Shelly docs | Wiring diagram + NZ install notes |
| Testing | Self-test on install | Bench-tested before shipping |
| Support | Community forums | Christchurch-based — info@calibrate.nz |
Outcome — Benefits
What changes in your home. Customer language, not spec sheet.
- Prevents mould and paint damage automatically
- No more forgotten fan — fully autonomous
- 15-minute smart overrun, extends on persistent humidity
- Local execution — works without internet
Spec — Features
How it works under the hood.
- Spike detection: 2% rise in 90s window
- Auto 15-min overrun with extend logic
- BLE humidity sensor (Shelly BLU H&T)
- Local Shelly script — no Home Assistant required (optional integration)
- Manual override still works via existing switch
Journey
What happens when you buy
You enquire
Hit Enquire — Shower Fan Solution — tell us your setup (fan model, opener, Wi-Fi). We confirm fit and price.
We build & test
We assemble, flash script, pair BLE, tune thresholds, bench-test on 192.168.1.x.
You install — we support
Sparky wires relay; you place sensor. Diagram + notes included. Support via info@calibrate.nz.
Trust
Built properly — no fabrication
Christchurch assembled
Built and bench-tested in Christchurch before shipping. Local support at info@calibrate.nz.
Bench tested
Verified on 192.168.1.x bench network — proven lineage from shower/scripts/shower-fan.js (2% / 90s / 15 min).
Electrician-friendly
Wiring diagram + install notes included. Shelly 1 Gen3 is 240V — electrician required for mains install. Sensor is DIY.
Warranty is Supplier warranty — TBC until confirmed with Shelly supplier. Prices marked TBC at enquiry.
Notes & lineage
Why this exists
NZ bathrooms are mould factories. This solution solves it with a proven script that has been running in a real Christchurch home — see shower/scripts/shower-fan.js lineage for the detection algorithm. Bench-tested on 192.168.1.x; lineage is FACT, not marketing.
What’s in the box
- Shelly 1 Gen3, preloaded with humidity-spike script
- Shelly BLU H&T, pre-paired
- Wiring diagram + install notes
- Test report (bench verification — TBC)
Installation
An electrician installs the Shelly 1 inline with your fan. You stick the BLU H&T on the wall. Done. No apps to configure unless you want to tweak thresholds.
Customisation
Thresholds (spikeThreshold, windowMs, onDurationMs) are documented and adjustable via the Shelly web UI. We ship sensible defaults (2% / 90s / 15 min — see lineage).
Ready to order Shower Fan Automation?
We build to order and test each system before shipping. Christchurch, NZ.
Works standalone • Expands to Home Assistant
Shower Fan Automation
Humidity-spike detection that runs your bathroom fan for you — no more mould, no more forgetting.