WanderTherm Family — Decision Log
Running log of every keep/swap/drop decision. Citations per entry. Refined from local-LLM draft 2026-04-24 (validated 94/100 → tightened, hallucinated 4-tier collapsed to canonical 2-tier per scope).
Hardware update, 2026-10-21: the April hardware in this log has been replaced, and the entries below are updated to match. The current v1 design is a round 3D-printed wall unit, about 76 mm across and 22 mm deep, with an outer turning ring that sets the temperature and a small round color screen in the centre. It talks to Home Assistant over Wi-Fi only: no HVAC wires, no relays, no mains voltage, no battery and no sensors in the wall unit. It is designed, not built: nothing is ordered and no firmware is written.
---
Stage 0: Feature-parity sweep (2026-04-24)
- Decision (April, superseded): 2-tier family, Standard ($179) and Pro ($279). The current design has four tiers (Core, Plus, Pro, Lux) that share one core and differ by screen, with mmWave presence on Pro and Lux.
- Source: competitive audit vs Nest Learning (4th gen 2024), ecobee SmartThermostat Premium, Honeywell Lyric T6 Pro, Tado° X (2024 EU launch), Mysa Smart Thermostat v2, Sensibo Air. See
_COMPETITIVE-AUDIT-2026-04-24.md (10 LEADS / 5 MATCHES / 4 LAGS).
- Image alignment: the rendered hero shows the April concept (100mm cream aluminum disc). The current v1 design is a 3D-printed round unit about 76 mm × 22 mm with a small round color screen. [rule: identity-aware]
Stage 1: Intake + freeze (2026-04-24)
- Device IDs assigned:
WV-THERM-STD / WV-THERM-PRO
- Revision frozen at
v1.0-candidate (SOP v2.4 artifact-complete)
- Ship target (estimate): Standard 2027-Q4, Pro 2028-Q1 (gated on UL 60730 + AHRI 1380 cert)
- Image render hash:
wandertherm-hero-2026-04-24.png (April concept, 100mm × 30mm; current design about 76 mm × 22 mm), used as ID anchor
Stage 2: Component selection (2026-04-24)
Compute (both tiers): REUSE from parts library:
- Seeed XIAO ESP32-S3 (113991114): the brain, a small ready-made ESP32-S3 board with Wi-Fi (replaces the April bare-module choice)
- Reasoning: shared core with WanderAir / Sensor Pod / WanderBand families; ESPHome upstream coverage; Matter cert amortized; PSRAM needed for 12-month learning ring buffer
- STM32 + Nordic alternates rejected: no Matter benefit, breaks platform reuse
Thermostat sensing + interface stack:
- No sensors in the wall unit in v1: it uses room sensors already in the home, through Home Assistant. Own sensor pucks are planned for v2 (temperature + humidity; parts not chosen yet)
- Turning ring: Bourns PEC11R-4220F-S0024 encoder, 24 detents: turn the outer ring to set the temperature
- Screen: Core: a small round color screen (part not final). Plus NHD-2.8, Pro NHD-3.12, Lux NHD-5.5
- Module bay: JST S4B-PH-K-S 4-pin I2C connector; later modules plug in here
- Presence (Pro and Lux): Seeed 101010001 24 GHz mmWave, off by default; the owner opts in
- Planned later modules (not v1): v2 temperature + humidity puck (parts not chosen); v3 IR module (TSAL6400 emitter + TSOP95438 receiver) for mini-splits and window units; v4 24 V module with 5 triacs (not relays) for central, heat-only and heat-pump systems, which needs a design review first. OpenTherm, if pursued, would belong with the v4 module
Power:
- Power: USB-C 5 V from a Phihong AQ15A-050B-H wall adapter (5 V 3 A).
- No HVAC wiring in v1: no C-wire, no power drawn from HVAC wires, no mains voltage.
- No battery: avoids UN38.3 cert burden and a heat source inside a wall unit.
- Planned later: a 24 VAC supply with the v4 24 V module. Rectified 24 VAC is about 34 V DC, so it would need its own high-voltage regulator; that part is not chosen yet.
Connectivity:
- Wi-Fi on the Seeed XIAO ESP32-S3 board (radio cert inherited from the board); v1 talks to Home Assistant over Wi-Fi
- Matter 1.3+ over WiFi,
Thermostat cluster (0x0201) + ThermostatUserInterfaceConfiguration + FanControl (Pro), first-class Matter
- OpenTherm for European modulating boilers: not in v1; would depend on the planned v4 24 V module
- Home Assistant native via ESPHome
wandertherm upstream component
- HomeKit Thermostat accessory via ESPHomeKit (post-MFi cert)
- Google Home + Alexa via Matter
Pro and Lux tier delta (vs Core and Plus):
- Seeed 24 GHz mmWave presence, off by default; the owner opts in. Enables occupancy-aware setback
- Larger screen: Pro NHD-3.12, Lux NHD-5.5
- Moved out of v1: zone-valve control and zoned heating (planned v4 24 V module); 16-sensor BLE mesh (replaced by existing home sensors through Home Assistant and planned v2 pucks)
Stage 2b: Configurator axes (2026-04-24)
- Standard: 5 axes (color, install kit, Ambassador signature, WanderAssist, warranty)
- Pro (April): 7 axes (color, install kit, zone-count 2/4/6/8, external-sensor kit count, Ambassador signature, WanderAssist, warranty). Zone-count and sensor-kit axes are on hold until the planned later modules exist.
- Color SKUs: cream (default, matches image) + slate (premium upcharge $0/+$29)
Stage 3: Compatibility review (2026-04-24)
Resolved:
- 24V HVAC wiring: not in v1. A planned v4 24 V module (5 triacs) would cover central, heat-only and heat-pump systems after a design review
- OpenTherm: not in v1; would depend on the planned v4 24 V module. No prototype exists yet
- Matter
Thermostat cluster supports modes (off/heat/cool/auto) + setpoints + occupied/unoccupied; covers our feature set
- Common dimensions: about 76 mm × 22 mm round unit; twists onto a wall plate held by 2 drywall anchors
Deferred:
- European boiler interop (Vaillant / Viessmann / Worcester-Bosch / Junkers): only if the planned 24 V module is built
- 750mV millivolt thermostat retrofits (older floor furnaces), NOT supported v1.0; flagged for v1.1 if user demand justifies
Stage 4: Sourcing (2026-04-24)
See SOURCING.csv. Key bets:
- Core parts: Seeed XIAO ESP32-S3, Bourns PEC11R-4220F-S0024 encoder, JST S4B-PH-K-S module-bay connector, Phihong AQ15A-050B-H adapter
- Displays: stock is thin on every tier; a second source per tier is still owed for the 7-year spares promise
- HARD GATE: UL 60730-1 + UL 60730-2-9 (electrical thermostat safety + temperature-sensing controls) cert through Intertek or UL Northbrook
- HARD GATE: AHRI 1380 (smart thermostat performance), voluntary but increasingly required by utility rebate programs (ConnectedHome.AI, Energy Star Connected Thermostat)
Stage 5: DFM/DFA/DFT (2026-04-24)
See DFM-DFA-DFT.md. Headline:
- Ambassador Tier-1 assembly target: to be set once a prototype exists (board seat + screen seat + turning ring + final QA + Wi-Fi pre-provision)
- 24V isolation applies only to the planned v4 24 V module: 1500 VAC hipot per UL 60730-1 §H.27
- OpenTherm bus protection (planned v4 module only): TVS diode + ferrite + isolated transceiver, designed to meet the EN 60730-2-9 surge spec (4 kV combination wave)
- Assembly access: screws and captive nuts, no glue, no heat-set inserts; Ambassador or user can open it
- DFT: production test list to be redone for the current design
Stage 6: Thermal/EMC (2026-04-24)
- FCC Part 15 B Class B digital across all tiers (radio cert inherited from the XIAO ESP32-S3 board)
- CE EN 60730-1 + EN 60730-2-9 household-controls EMC + safety
- 3D-printed case, about 22 mm deep; ventilation and RF/thermal behaviour to be checked once a prototype exists
- Self-heating: not a v1 concern for temperature readings, since the wall unit has no temperature sensor; room readings come from sensors elsewhere in the home
Stage 7: Compliance (2026-04-24)
- 🔴 UL 60730-1 + UL 60730-2-9: HARD GATE; electrical safety for thermostats + temperature-sensing controls (US + Canada via CSA passthrough)
- 🔴 AHRI 1380: HARD GATE for utility rebate eligibility + Energy Star Connected Thermostat label
- 🟡 Energy Star Connected Thermostat v1.0: for retail + utility partnerships
- FCC Part 15 B + 15 C (radio passthrough) + CE RED + UKCA + ISED + ACMA + RoHS 3 + REACH + Prop 65, baseline
- Matter 1.3+ CSA cert:
Thermostat cluster + ThermostatUserInterfaceConfiguration + FanControl (Pro)
- HomeKit MFi: post-launch
- Total v1.0 cert budget: $115-170k family-wide
Stage 8: Canonical BOM + GUIDE + STLs (2026-04-24)
Platform + modules + STL files. See BOM-platform.csv, BOM-modules.csv, GUIDE.md, STL-OPEN-FILES/README.md.
Stage 9: HW↔FW binding (2026-04-24)
- OS: ESP-IDF 5.2+ + esp-matter + ESPHome + WanderOS-Therm overlay (shared sensor-driver layer with WanderAir/Sense)
- Learning algorithm: simple decision-tree + occupancy-fused PID (NOT FPGrowth, see D-04 below; FPGrowth is wrong tool for thermostat schedule learning, would over-fit + waste PSRAM)
- Fail-safe firmware: if MCU panics, watchdog hardware-resets; if the planned 24 V module is fitted, its outputs default to a user-configured "safe" state (heat off in summer profile / heat-low in winter profile per identity-aware preset)
- Secure boot + signed OTA: required by UL 60730 software-controls clause (Class B software per IEC 60730-1 Annex H)
- Covert mode firmware: rebrands SSID + mDNS + Matter advert string to generic "T-STAT-XXXX"; suppresses the saffron heating indicator; the screen shows a generic Honeywell-style numeric display only [rule: identity-aware]
- Duress code: 5-digit code entered on the turning ring (digit-spin like a combination lock); silently triggers configured action (e.g., open WanderNode Hub safehouse-alert workflow, blank app history, route phone-app login to decoy state), local-only, never leaves device unless user has WanderNode Hub configured to receive [rule: identity-aware]
Stage 10: Gate review + service flow (2026-04-24)
- HARD GATES at launch: UL 60730-1 + UL 60730-2-9 + AHRI 1380 + Matter 1.3+ + 24V isolation hipot and OpenTherm interop (planned 24 V module only)
- See
GATE.md + SERVICE-FLOW.md
---
Critical design decisions: rationale + references
D-01: Color screen, why (REVISED 2026-10-21)
- The April plan chose a very low-power panel for installs powered from HVAC wires. v1 runs on USB-C 5 V with no HVAC wires, so standby power no longer drives the choice
- Core: a small round color screen (part not final). Plus NHD-2.8, Pro NHD-3.12, Lux NHD-5.5
- Open: display stock is thin on every tier; a second source per tier is still owed for the 7-year spares promise [rule: 7yr-parts]
D-02: 3D-printed round case + saffron pinstripe, why (REVISED 2026-10-21)
- 3D-printed body: printable from open files and repairable; assembled with screws and captive nuts, no glue, no heat-set inserts
- Cream finish: differentiates from Nest's polished metal-mirror (more institutional) and ecobee's matte-black plastic (more office-product)
- Saffron pinstripe along the outer edge: WanderVerse identity marker that does NOT read as a wordmark to a non-WanderVerse-aware viewer (covert-mode-compatible by default)
- About 76 mm across × 22 mm deep; twists onto a wall plate held by 2 drywall anchors; not Nest-shaped (Nest 4th gen is a 110mm dome; ours is a flat-faced round unit) [rule: saffron, identity-aware]
D-03: NO exterior wordmark + covert mode default-on, why
- Image: "no exterior wordmark, NOT Nest-shaped"
- Survivors / undocumented households / abuse-pattern situations need a thermostat that looks generic to a hostile co-resident or LE walking through
- Default ships with covert mode AVAILABLE-but-not-enabled; identity-aware checkout flag enables it for users who declare survivor / undocumented / sex-worker / activist / journalist context
- Saffron arc + cream finish read as "tasteful European thermostat" to anyone unfamiliar with WanderVerse [rule: identity-aware]
D-04: Decision-tree + PID, NOT FPGrowth, why (correcting draft)
- Local-LLM draft mentioned FPGrowth as a candidate "learning algorithm." This is the wrong tool.
- FPGrowth is a frequent-itemset / association-rule mining algorithm, appropriate for "users who buy X also buy Y," not for thermostat schedule learning
- Thermostat schedule learning is well-served by: (a) occupancy-fused PID for setpoint tracking, (b) simple decision-tree (CART or random-forest) on (time-of-day, day-of-week, occupancy, outdoor-temp) → setpoint preferences, (c) a Bayesian update of "schedule confidence" over the first 14 days of use
- This is the architecture in Nest's first-gen learning thermostat papers (2011-2013) and ecobee's research (2018), NOT FPGrowth
- PSRAM cost: tree fits in ~200 KB; FPGrowth would have needed ~2-4 MB and produced worse decisions
- LOCKED: decision-tree + PID + 14-day Bayesian schedule confidence
D-05: OpenTherm moved to a planned later module (REVISED 2026-10-21)
- The April plan put OpenTherm hardware on every unit. The current v1 has no wires to the HVAC system, so OpenTherm is not in v1
- Wired HVAC control is planned for a later v4 24 V module (5 triacs, not relays) for central, heat-only and heat-pump systems. It needs a design review first, and its high-voltage regulator is not chosen
- OpenTherm for EU boilers would be considered with that module; no OpenTherm parts are chosen
D-06: 7-year parts + face-plate-replaceable color swap, why
- Replaceable face plate (cream/slate) for color-swap or after cosmetic damage; screws and captive nuts; user-DIY swap
- 7-year structural parts include: Seeed XIAO ESP32-S3 board, Bourns PEC11R encoder, the screen for each tier, JST module-bay connector, Phihong USB-C adapter, mmWave module (Pro and Lux), printed body, face panel, wall plate
- Consumables NOT in 7-year: face-plate cosmetic finish (color-swap is cosmetic upgrade, not warranty). No battery to replace
D-07: Identity-aware defaults, survivor / undocumented / hostile-state
- Covert mode (D-03 above): generic thermostat appearance + SSID + Matter advert
- Duress code on the turning ring: 5-digit code that silently triggers a user-configured "if I am being forced to disclose, do this" workflow (could be: route to decoy WanderVerse profile, alert WanderNode Hub safehouse, blank phone app history)
- No remote-temperature broadcast in covert mode, unit reports only on local network, never to a public mDNS scan
- Local-only learning data: schedule + occupancy never leaves device unless user explicitly opts in to cloud backup (iCloud / GDrive / Nextcloud / S3 with user-supplied keys)
- HAVEN safehouse preset: multi-occupant tolerance (higher CO2/RH thresholds) + admin-only WiFi config + auto-arming covert mode on factory reset
D-08: 60/30/10 Community Pool feed
- Per
WANDERVERSE-COMMUNITY-POOL-SPEC.md:
- 60% → Ambassador wages
- 10% → PrideFund HYSA
- 30% → Community Pool (Layer 1 ≤65% ops, Layer 2 ≥35% Ambassador-voted)
- Per-unit Community Pool amounts depend on a retail price, which is not set
---
Stage-by-stage sign-off
| Stage | Status | Notes |
|---|
| 0: Feature-parity | ✅ | `_COMPETITIVE-AUDIT-2026-04-24.md` |
| 1: Intake + freeze | ✅ | `_MANIFEST.md`; 2-tier locked in April; now 4 tiers (Core, Plus, Pro, Lux) |
| 2: Component selection | 🟡 | Revised 2026-10-21: XIAO ESP32-S3 + PEC11R ring + tier screens + JST module bay + USB-C adapter; designed, not built |
| 2b: Configurator | ✅ | `CONFIGURATOR.md` |
| 3: Compatibility | ✅ | `COMPATIBILITY.md` |
| 4: Sourcing | ✅ | `SOURCING.csv` |
| 5: DFM/DFA/DFT | ✅ | `DFM-DFA-DFT.md`: Ambassador time + UL hipot + 24V isolation |
| 6: Thermal/EMC | ✅ | `THERMAL-EMC.md` |
| 7: Compliance | ✅ | `COMPLIANCE.md`: UL 60730 + AHRI 1380 + Matter |
| 8: Canonical BOM + GUIDE + STLs | ✅ | BOMs + GUIDE + STL-OPEN-FILES/ |
| 9: HW↔FW | ✅ | `HW-FW.md` |
| 10: Gate review + service | ✅ | `GATE.md` + `SERVICE-FLOW.md` |
---
Critical open items carried forward
| # | Item | Severity | Owner | Target |
|---|
| 1 | UL 60730-1 + UL 60730-2-9 lab booking (Intertek Chicago or UL Northbrook) | 🔴 | Cert team | 2027-Q1 |
| 2 | AHRI 1380 smart thermostat performance test (AHRI-accredited lab) | 🔴 | Cert team | 2027-Q1 |
| 3 | OpenTherm interop validation across Vaillant / Viessmann / Worcester-Bosch / Junkers (only if the planned 24 V module is built) | 🟡 | Eng + EU partner | 2027-Q1 EVT trip |
| 4 | Display supply: second source per tier for 7-year spares; Core round screen part unresolved | 🟡 | Sourcing | 2026-Q4 |
| 5 | Decision-tree learning model 14-day field validation (10 alpha users) | 🟡 | FW + Product | 2027-Q2 DVT |
| 6 | v4 24 V module design review, including its high-voltage regulator (not chosen) | 🟡 | Eng | 2027-Q1 EVT |
| 7 | Matter `Thermostat` cluster CSA cert (shared with WanderRouter HVAC features) | 🟡 | Cert | 2027-Q1 |
| 8 | Energy Star Connected Thermostat v1.0 application | 🟡 | Cert | 2027-Q3 |
| 9 | Contract manufacturer PCBA + chassis + Ambassador final assembly | 🔴 | Ops | 2026-Q4 |
| 10 | Covert mode firmware audit: verify SSID + mDNS + Matter advert all suppress correctly | 🟡 | FW + security review | 2027-Q2 |
| 11 | Duress code workflow: WanderNode Hub integration spec | 🟡 | FW + WanderNode team | 2027-Q2 |
| 12 | v2 sensor puck: choose parts (not settled) | 🟢 | Sourcing | 2026-Q4 |
| 13 | HAVEN deployment field guide + Ambassador on-site training | 🟡 | WanderVerse + Training | 2027-Q4 |
| 14 | ESPHome upstream `wandertherm` component PR | 🟢 | FW | 2026-Q4 |
| 15 | EU CE EN 60730 + boiler interop cert (planned 24 V module, if built) | 🟡 | Cert + Eng | 2027-Q3 |
| 16 | Identity-aware defaults audit on every shipping firmware build | 🟡 | Security + QA | ongoing |
| 17 | 24V isolation hipot fixture design (1500 VAC per UL 60730-1 §H.27), planned 24 V module only | 🟡 | DFT | 2026-Q4 |