Installer Commissioning Guide

This guide is intended for qualified heating installers and engineers commissioning the Therma One T1 thermostat. It covers wiring, OpenTherm configuration, heat call verification, connectivity checks, and the customer handover process.

1. Wiring reference

The T1 wall plate has six screw terminals. Use the following terminal assignments:

• L — Live in (230V AC, brown wire from junction box or boiler)
• N — Neutral (230V AC, blue wire)
• COM — Common relay output (connects to boiler call-for-heat input)
• NO — Normally open relay contact (connects to boiler call-for-heat return). The relay closes when the T1 calls for heat.
• OT+ — OpenTherm positive (if using OpenTherm, connect to boiler OT+ terminal)
• OT- — OpenTherm negative (if using OpenTherm, connect to boiler OT- terminal)

For relay-only installations (no OpenTherm), leave OT+ and OT- disconnected. The T1 auto-detects whether OpenTherm is present at first boot.

2. OpenTherm setup

1. Verify boiler compatibility. Check the OpenTherm compatibility list at support.monverta.com/opentherm or in the reference article on this site. The boiler must support OpenTherm protocol v2.2 or later.
2. Connect OT+ and OT-. Run a two-core cable (minimum 0.5 mm²) between the T1 wall plate OT terminals and the boiler's OpenTherm terminals. Polarity is not critical — OpenTherm is polarity-independent.
3. Power on and confirm detection. After restoring power, the T1 will display "OpenTherm detected" during its boot sequence. If this message does not appear, check wiring continuity with a multimeter.
4. Configure modulation range. Navigate to Settings > Installer > OpenTherm > Modulation. Set the minimum and maximum flow temperatures appropriate for the system (e.g., 30°C min, 75°C max for a radiator system). For underfloor heating, set max to 45°C.
5. Enable DHW priority (if applicable). If the boiler provides domestic hot water, enable DHW priority at Settings > Installer > OpenTherm > DHW Priority. This ensures hot water takes precedence over central heating calls.

3. Testing the heat call

1. Enter test mode. On the T1, go to Settings > Installer > Test Mode. Enter the installer PIN (default: 1234). The test mode screen provides manual relay and OpenTherm controls.
2. Test relay operation. Tap Relay ON. Verify the boiler fires within 10 seconds. Check that the flame icon appears on the T1 display. Tap Relay OFF and confirm the boiler shuts down.
3. Test OpenTherm modulation. If OpenTherm is connected, use the flow temperature slider in test mode. Set it to 50°C and verify the boiler modulates to approximately that flow temperature (allow 60 seconds for stabilisation). The T1 displays the actual boiler flow temperature reported via OpenTherm.
4. Check room temperature reading. Compare the T1's displayed room temperature against an independent thermometer placed nearby. The T1 sensor accuracy is +/-0.3°C. If the reading is offset, apply a calibration adjustment at Settings > Installer > Sensor Calibration (range: -3.0°C to +3.0°C).

4. Verifying connectivity

1. Connect to Wi-Fi. If the customer's Wi-Fi is available, connect the T1 during commissioning. Go to Settings > Wi-Fi and select the network. Confirm the Wi-Fi icon appears on the home screen.
2. Check cloud connectivity. Navigate to Settings > About > Cloud Status. The status should read "Connected" with a timestamp of the last sync. If it reads "Disconnected," verify the router allows outbound HTTPS traffic on port 443.
3. Firmware update. If a firmware update is available, the T1 will display a notification. Apply the update before handover — updates take approximately 3 minutes and the unit will reboot once.

5. Customer handover checklist

• Confirm the T1 is displaying the correct room temperature
• Demonstrate a manual temperature adjustment on the thermostat
• Show the customer how to install the Monverta Home app and pair the device
• Help the customer create an initial heating schedule (or set up a default schedule)
• Explain the location of the QR code (back of unit) for product registration
• Provide the customer with the Quick Start card from the box
• Change the installer PIN from the default if the customer requests it (Settings > Installer > Change PIN)
• Record the device serial number (MV-T1-XXXXX) on the installation certificate