# Thermia Diplomat heat pump control via Homey **URL:** \ **Category:** Devices\ **Tags:** homeyscript, flow, homey-pro\ **Created:** [March 20, 2026, 4:21pm UTC](https://community.homey.app/t/thermia-diplomat-heat-pump-control-via-homey/152739 "2026-03-20T16:21:06Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![bentrik](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/bentrik/32/120862_2.png) [@bentrik](https://community.homey.app/u/bentrik)\ **Post date:** [March 20, 2026, 4:21pm UTC](https://community.homey.app/t/thermia-diplomat-heat-pump-control-via-homey/152739/1 "2026-03-20T16:21:06Z")
I wanted to control the hot water production on my Thermia Diplomat Inverter M heat pump from Homey Pro, but there was no official Homey app available. After some digging through the Thermia Online web app using browser DevTools, I managed to reverse-engineer the API and build a working HomeyScript integration. Sharing it here in case others find it useful. Tested on: - Homey Pro 2026 - Thermia Diplomat Inverter M [230] - Thermia Online account (online.thermia.se) * * * **What it does** - Turns hot water production ON or OFF via Homey Flows - Reads temperatures from the heat pump every 10 minutes (outdoor, supply line, brine in, hot water) - Stores temperatures as Homey Logic variables — visible in Insights with graphs over time - Auto-renews the authentication token so it never expires - Sends a push notification if authentication fails My setup turns hot water OFF at 06:00 and ON again at 22:00 to avoid peak electricity hours, with a safety flow that turns it back on if the water temperature drops below 50°C during the day. * * * **Prerequisites** - HomeyScript app installed on your Homey - A Thermia Online account at online.thermia.se - A PC/Mac browser with DevTools (Chrome or Edge recommended) - Basic familiarity with Homey Flows * * * **Step 1 — Get your refresh token** The Thermia API uses token-based authentication. You need to get an initial refresh token from your browser: 1. Go to online.thermia.se and log in 2. Open DevTools (F12) → Network tab 3. Refresh the page 4. Find the request named **token** in the list 5. Click it → **Response** tab 6. Copy the value of the `refresh_token` field — it is a long ~1400 character string with 5 dot-separated segments starting with `eyJ` ⚠ Do not copy the `access_token` or `id_token` — these are shorter 3-part strings and will not work. * * * **Step 2 — Find your installation ID** 1. In DevTools with the Network tab still open, look for requests with URLs containing `/installationstatus/` or `/Registers/Installations/` 2. Your installation ID is the number in those URLs — for example `/Registers/Installations/XXXXXXX/Groups/` 3. Note this number — you will need to replace `XXXXXXX` with it in the scripts below * * * **Step 3 — Create Homey Logic variables** Create these variables in Homey → Logic → Variables: | Name | Type | | --- | --- | | `thermia_refresh_token` | Text | | `thermia_hotwater_command` | Text | | `thermia_hotwater_status` | Text | | `thermia_temp_hot_water` | Number | | `thermia_temp_outdoor` | Number | | `thermia_temp_supply` | Number | | `thermia_temp_brine_in` | Number | * * * **Step 4 — Store the refresh token** Create a new HomeyScript called `thermia_set_token` and run it once with your token pasted in: javascript ```auto const newRefreshToken = "PASTE_YOUR_REFRESH_TOKEN_HERE"; const allVars = Object.values(await Homey.logic.getVariables()); const refreshVar = allVars.find(v => v.name === "thermia_refresh_token"); await Homey.logic.updateVariable({ id: refreshVar.id, variable: { value: newRefreshToken } }); log("Stored length: " + newRefreshToken.length); log("Segments: " + newRefreshToken.split(".").length); log("✅ Done — expect length ~1400 and segments 5"); ``` * * * **Step 5 — The scripts** ⚠ Replace `XXXXXXX` with your own installation ID in both scripts before running them. **Script 1: `thermia_read_temperatures`** javascript ```auto const token_var = await Homey.logic.getVariables(); const allVars = Object.values(token_var); const refreshVar = allVars.find(v => v.name === "thermia_refresh_token"); const loginBody = new URLSearchParams(); loginBody.append("grant_type", "refresh_token"); loginBody.append("client_id", "09ea4903-9e95-45fe-ae1f-e3b7d32fa385"); loginBody.append("refresh_token", refreshVar.value.trim()); loginBody.append("redirect_uri", "https://www.online.thermia.se/login"); const loginRaw = await fetch("https://thermialogin.b2clogin.com/thermialogin.onmicrosoft.com/b2c_1a_signuporsigninonline/oauth2/v2.0/token", { method: "POST", headers: { "Content-Type": "application/x-www-form-urlencoded" }, body: loginBody }); const loginData = JSON.parse(await loginRaw.text()); if (!loginData.access_token) { log("❌ Token refresh failed - paste a new refresh_token into Homey Logic"); log(JSON.stringify(loginData)); await Homey.notifications.createNotification({ excerpt: "⚠️ Thermia token expired — paste a new refresh_token into Homey Logic" }); return; } if (loginData.refresh_token) { await Homey.logic.updateVariable({ id: refreshVar.id, variable: { value: loginData.refresh_token } }); log("✅ Refresh token renewed (" + loginData.refresh_token.length + " chars)"); } const BASE = "https://online-classic-serviceapi.azurewebsites.net/api/v1"; const INSTALL = "XXXXXXX"; // ← Replace with your installation ID const headers = { "Authorization": "Bearer " + loginData.access_token, "Accept": "application/json" }; const res = await fetch(BASE + "/Registers/Installations/" + INSTALL + "/Groups/REG_GROUP_TEMPERATURES", { headers }); const data = JSON.parse(await res.text()); const mapping = { "REG_HOT_WATER_TEMPERATURE": "thermia_temp_hot_water", "REG_OUTDOOR_TEMPERATURE": "thermia_temp_outdoor", "REG_SUPPLY_LINE": "thermia_temp_supply", "REG_BRINE_IN": "thermia_temp_brine_in" }; for (const reg of data) { const varName = mapping[reg.registerName]; if (!varName) continue; const homeyVar = allVars.find(v => v.name === varName); if (!homeyVar) { log("⚠️ Variable not found: " + varName); continue; } await Homey.logic.updateVariable({ id: homeyVar.id, variable: { value: reg.registerValue } }); log(varName + " = " + reg.registerValue + "°C"); } ``` **Script 2: `thermia_hotwater`** javascript ```auto // ── CONFIGURATION ─────────────────────────────────────────────── const CLIENT_ID = "09ea4903-9e95-45fe-ae1f-e3b7d32fa385"; const TOKEN_URL = "https://thermialogin.b2clogin.com/thermialogin.onmicrosoft.com/b2c_1a_signuporsigninonline/oauth2/v2.0/token"; const REDIRECT = "https://www.online.thermia.se/login"; const BASE = "https://online-classic-serviceapi.azurewebsites.net/api/v1"; const INSTALL = "XXXXXXX"; // ← Replace with your installation ID const REG_SPEC_ID = 29442; // Hot water on/off register — may differ on other models // ── STEP 1: READ HOMEY LOGIC VARIABLES ────────────────────────── const allVars = Object.values(await Homey.logic.getVariables()); const refreshVar = allVars.find(v => v.name === "thermia_refresh_token"); const commandVar = allVars.find(v => v.name === "thermia_hotwater_command"); const statusVar = allVars.find(v => v.name === "thermia_hotwater_status"); if (!refreshVar) { log("❌ Missing variable: thermia_refresh_token"); return; } if (!commandVar) { log("❌ Missing variable: thermia_hotwater_command"); return; } const command = (commandVar.value || "").trim().toLowerCase(); log("Command: " + command); // ── STEP 2: AUTHENTICATE WITH THERMIA ─────────────────────────── const loginBody = new URLSearchParams(); loginBody.append("grant_type", "refresh_token"); loginBody.append("client_id", CLIENT_ID); loginBody.append("refresh_token", refreshVar.value.trim()); loginBody.append("redirect_uri", REDIRECT); const loginRaw = await fetch(TOKEN_URL, { method: "POST", headers: { "Content-Type": "application/x-www-form-urlencoded" }, body: loginBody }); const loginData = JSON.parse(await loginRaw.text()); if (!loginData.access_token) { log("❌ Token refresh failed - paste a new refresh_token into Homey Logic"); log(JSON.stringify(loginData)); await Homey.notifications.createNotification({ excerpt: "⚠️ Thermia token expired — paste a new refresh_token into Homey Logic" }); return; } if (loginData.refresh_token) { await Homey.logic.updateVariable({ id: refreshVar.id, variable: { value: loginData.refresh_token } }); log("✅ Refresh token renewed (" + loginData.refresh_token.length + " chars)"); } const headers = { "Authorization": "Bearer " + loginData.access_token, "Accept": "application/json", "Content-Type": "application/json" }; // ── STEP 3: READ CURRENT HOT WATER STATE ──────────────────────── const getRes = await fetch(BASE + "/Registers/Installations/" + INSTALL + "/Groups/REG_GROUP_HOT_WATER", { headers }); const getData = JSON.parse(await getRes.text()); const currentValue = getData[0].registerValue; log("Current: " + (currentValue === 1 ? "ON" : "OFF")); // ── STEP 4: HANDLE "STATUS" COMMAND ───────────────────────────── if (command === "status") { const s = currentValue === 1 ? "on" : "off"; if (statusVar) await Homey.logic.updateVariable({ id: statusVar.id, variable: { value: s } }); log("Status: " + s); return s; } // ── STEP 5: VALIDATE THE COMMAND ──────────────────────────────── const targetValue = command === "on" ? 1 : command === "off" ? 0 : -1; if (targetValue === -1) { log("❌ Unknown command: " + command + " (use on/off/status)"); return; } // ── STEP 6: SKIP IF ALREADY IN TARGET STATE ────────────────────── if (currentValue === targetValue) { log("Already " + command.toUpperCase() + " — no change needed"); return command; } // ── STEP 7: SEND THE COMMAND TO THE HEAT PUMP ─────────────────── const uuid = "xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx".replace(/[xy]/g, c => { const r = Math.random() * 16 | 0; return (c === "x" ? r : (r & 0x3 | 0x8)).toString(16); }); const postRes = await fetch(BASE + "/Registers/Installations/" + INSTALL + "/Registers", { method: "POST", headers, body: JSON.stringify({ registerSpecificationId: REG_SPEC_ID, registerValue: targetValue, clientUuid: uuid }) }); log("Set " + command.toUpperCase() + ": HTTP " + postRes.status); // ── STEP 8: SAVE THE NEW STATE TO HOMEY ───────────────────────── if (statusVar) { await Homey.logic.updateVariable({ id: statusVar.id, variable: { value: command } }); } return command; ``` * * * **Step 6 — Set up Flows** **Temperature polling (every 10 minutes):** - WHEN: Every 10 minutes - THEN: Run script `thermia_read_temperatures` **Hot water OFF at 06:00:** - WHEN: Time is 06:00 - THEN: Set `thermia_hotwater_command` to `off` - THEN: Run script `thermia_hotwater` **Hot water ON at 22:00:** - WHEN: Time is 22:00 - THEN: Set `thermia_hotwater_command` to `on` - THEN: Run script `thermia_hotwater` **Optional — Safety rescue if water gets too cold:** - WHEN: Every 10 minutes - AND: Time is between 06:01 and 21:59 - AND: `thermia_temp_hot_water` is less than 50 - THEN: Set `thermia_hotwater_command` to `on` - THEN: Run script `thermia_hotwater` * * * **Notes** - The `client_id` in the scripts is the public Thermia Online app ID — it is the same for all users and not a secret - The `REG_SPEC_ID` (29442) is the register ID for hot water on/off on the Diplomat Inverter M — it may be different on other Thermia models. If it doesn’t work, check the DevTools network traffic when toggling hot water in the Thermia web app and look for the `registerSpecificationId` value in the POST request payload - The refresh token auto-renews on every script run, so you should never need to paste a new one manually as long as the polling flow runs at least once a day - Temperature graphs appear automatically in Homey Insights once the polling flow has been running for a while ---
**Author:** ![system](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/system/32/1_2.png) [@system](https://community.homey.app/u/system)\ **Post date:** [March 20, 2026, 4:22pm UTC](https://community.homey.app/t/thermia-diplomat-heat-pump-control-via-homey/152739/2 "2026-03-20T16:22:55Z")
Unlisted on March 20, 2026, 4:22pm UTC ---
**Author:** ![system](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/system/32/1_2.png) [@system](https://community.homey.app/u/system)\ **Post date:** [March 21, 2026, 4:11am UTC](https://community.homey.app/t/thermia-diplomat-heat-pump-control-via-homey/152739/3 "2026-03-21T04:11:15Z")
Listed on March 21, 2026, 4:11am UTC ---
**Author:** ![FlorisVandeVijver](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/florisvandevijver/32/60097_2.png) [@FlorisVandeVijver](https://community.homey.app/u/FlorisVandeVijver)\ **Post date:** [March 21, 2026, 10:43am UTC](https://community.homey.app/t/thermia-diplomat-heat-pump-control-via-homey/152739/4 "2026-03-21T10:43:09Z")
an alternative would be to use husdata hardware ([https://husdata.se](https://husdata.se)) with husdata app ( [Husdata | Homey](https://homey.app/en-be/app/se.husdata/Husdata/) ) which works for different types of heatpumps, including Thermia ---
**Author:** ![bentrik](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/bentrik/32/120862_2.png) [@bentrik](https://community.homey.app/u/bentrik)\ **Post date:** [March 22, 2026, 8:39am UTC](https://community.homey.app/t/thermia-diplomat-heat-pump-control-via-homey/152739/5 "2026-03-22T08:39:16Z")
I did find that solution before trying this, but thought it was unnecessary to buy additional hardware when the web interface existed. That said though, I still struggle a bit with the token expiration. The best would be to find a way for homey to log in with my credentials, but I haven’t found a way to do so yet.