DSVT (Dual Smart Virtual Thermostat) – Multi-Zone Heating, Cooling and DHW Plugin for Domoticz

[szelessavmuhely]

## Important installation and configuration instructions

Before using DSVT for the first time, please follow these steps carefully. These requirements are particularly important for new Domoticz installations.

### 1. Required Domoticz settings

**Geographical location**

Open **Setup → Settings → System** and enter the actual latitude and longitude of your installation.

DSVT uses these coordinates for location-dependent weather forecasts and temperature calculations. Incorrect or missing coordinates may result in inaccurate heating and cooling control.

domoticz-location.png (362.43 KiB) Viewed 470 times

**Local API access**

Open **Setup → Settings → Security → Trusted Networks (no username/password)** and add:

`127.0.0.1`

Click **Apply Settings** to save the configuration.

This setting is essential because DSVT communicates with the local Domoticz API to create and update user variables and perform other control operations.

Without this permission, Domoticz may reject API requests with **401 Unauthorized**, preventing important parts of DSVT from functioning correctly.

domoticz-local-networks.png (372.06 KiB) Viewed 470 times

### 2. Create the DSVT hardware first

Open **Setup → Hardware** and select:

**DSVT + HMV (DHW) + 12 ZONE**

Create the hardware entry with the optional configuration fields left empty. Do not attempt to configure all zones and devices at this stage.

Click **Add** to create the plugin.

**Important: The dedicated DSVT HTML configuration interface becomes available only after the DSVT hardware has been created.**

dsvt-html-setup-1.png (55.46 KiB) Viewed 470 times

### 3. Configure DSVT using the HTML interface

After creating the hardware, open:

**Custom → HTML setup!**

This is the dedicated administration interface for configuring the heating and cooling zones, heat sources, DHW, buffer tanks, mixing valves, sensors and other operating parameters.

**Do not try to perform the detailed configuration through the standard Domoticz hardware settings.** Those fields are not intended for the complete DSVT configuration.

**Important: Check your Domoticz user permissions.**

The Custom menu may not be accessible to ordinary users by default. Make sure the account you are using has sufficient permissions to view and access the Custom menu.

If the HTML setup page is not visible, first check that the DSVT hardware has been created, the HTML interface files have been installed correctly, and your user account has the necessary access rights.

### Documentation

The complete installation instructions, configuration guide and additional screenshots are available on GitHub:

https://github.com/szelessavalapitvany/Domoticz-DSVT

Please follow this installation sequence to avoid unnecessary configuration and initialization problems.

[szelessavmuhely]

**Important installation update**

Apologies, we overlooked a few installation details that have become routine for us after years of working with Domoticz.

In particular, we did not initially mention two important settings:

- Configuring the actual geographical coordinates in Domoticz.
- Allowing local API access for `127.0.0.1` under **Setup → Settings → Security → Trusted Networks**.

We also clarified the initial setup procedure: DSVT hardware must first be created with empty configuration fields. Only then does the dedicated HTML configuration interface become available under the **Custom** menu.

Please also make sure your user account has permission to access the Custom menu.

These details are particularly important for fresh Domoticz installations and may otherwise cause initialization or configuration problems.

**We have now updated the first post with detailed instructions and screenshots**, and the GitHub README has been updated as well.

https://github.com/szelessavalapitvany/Domoticz-DSVT

Thank you for your patience and understanding. We appreciate any feedback, especially from users installing DSVT on a fresh system.

[szelessavmuhely]

**Bug fix – Selector Switch initialization on fresh Domoticz installations**

During testing on a fresh Domoticz 2025.2 installation, we discovered an initialization issue that may also affect certain other Domoticz versions.

Some Selector Switch devices could appear as **"undefined"** or **"Invalid?"** instead of displaying their configured default state.

The issue was related to the initial `nValue` and `sValue` combination used when creating these devices.

For example, the previous initialization was:

`devicecreated.append(deviceparam(2, 0, "10"))`

The corrected initialization is:

`devicecreated.append(deviceparam(2, 1, "10"))`

For Selector Switch devices initialized in an active state, `nValue` is now set to `1`, while switches initialized in the Off state retain `nValue=0`.

**The fix has been committed to GitHub.**

Users are advised to update the DSVT plugin to the latest version.

Repository:
https://github.com/szelessavalapitvany/Domoticz-DSVT

Thank you for your patience as we continue testing DSVT on clean Domoticz installations.

[szelessavmuhely]

DSVT v1.3.0 – Frost Protection and Pump Anti-Seize Protection

Hello everyone,

I've released DSVT version 1.3.0 (2026-10-20), introducing two new protection features for heating and cooling systems.

1. Frost Protection

DSVT can now monitor one or more temperature sensors to help protect heating system components against freezing.

• Multiple temperature sensors can be configured (FG_T).
• The average temperature of the configured sensors is used.
• Configurable temperature limit and hysteresis through Domoticz setpoint devices.
• One or more switches can be controlled automatically (FG_S).
• Switches turn ON when the temperature reaches or falls below the configured limit and OFF when it reaches the limit plus hysteresis.
• Invalid or timed-out sensor readings are excluded from the average.

2. Circulation Pump Anti-Seize Protection

Circulation pumps that remain inactive for long periods can become stuck, particularly outside the heating season.

DSVT now supports automatic weekly pump exercise to help prevent this.

Configurable parameters:

• SV_P – Circulation pump switch IDs
• SV_D – Day of the week (0 = Monday, 6 = Sunday)
• SV_H – Scheduled starting hour (0–23)
• SV_M – Pump running duration in minutes (1–20)

The protection starts once per scheduled week within a one-hour starting window.

The run expiry timestamp is saved persistently, preventing duplicate activation after restarting the plugin or Domoticz.

After the configured running time, the protection requests an OFF command through the normal DSVT switching system.

3. Integration with Existing Control Logic

Both protection functions use DSVT's existing switch command handling.

ON commands have priority over OFF commands.

This means that normal heating or cooling demand can keep a pump running even after the protection cycle has finished.

The protection functions therefore work alongside the normal heating and cooling control logic.

4. Configuration

I recommend using the dedicated HTML configuration interface under the Domoticz Custom menu rather than manually editing the plugin's hardware parameters.

Both protection features are included in DSVT v1.3.0.

Feedback and testing on different heating systems and Domoticz installations are welcome!

GitHub:
DSVT GitHub Repository

Documentation:
DSVT Documentation