> For the complete documentation index, see [llms.txt](https://wiki.inels.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://wiki.inels.com/inels-bus/inels-design-manager-idm3/ntp-time-synchronization-settings.md).

# NTP (Time Synchronization) Settings

The **miniCU** supports automatic time synchronization using **NTP (Network Time Protocol)**.\
Correct system time is important for:

* Scheduled automations (time scenes, logic)
* Logs and event timestamps
* Time-based reporting
* Reliable integration with external systems

NTP settings are configured in **iDM (iNELS Design Manager)** inside the CU configuration section.

### Where to Configure NTP in iDM

1. Open **iDM**
2. Connect to the target **miniCU**
3. Navigate to:

**CU Configuration → Time Settings**

In this page, you will find a field to configure **NTP server**.

<figure><img src="https://407891681-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FErjlplToL8l7jIChGVB2%2Fuploads%2FNfE5Uuc3YRFeDeGCuncU%2FNTP.png?alt=media&amp;token=79786721-546e-43fa-b96f-2d1b7bbbec42" alt=""><figcaption></figcaption></figure>

**Only IP address format is supported** in the NTP server field.

* The miniCU NTP input supports **numeric IP address only**
* DNS strings / hostnames are **not supported**

&#x20;`195.113.144.201`\
&#x20;`81.0.246.244`

#### Not Supported Example

❌ `pool.ntp.org`\
❌ `time.google.com`\
❌ `0.pool.ntp.org`

> ⚠️ **Do not use string-based NTP servers** like `pool.ntp.org`.\
> The miniCU will not resolve the DNS name and time sync will fail.

## **Real-Time Clock (RTC) Backup — Power Loss Behavior**

The miniCU maintains its real-time clock using a supercapacitor rather than a battery. This supercapacitor keeps the date and time running for approximately **3–4 days** after mains power is removed.

If the unit remains without power beyond this window, the RTC will lose its date/time reference. On the next power-up, the miniCU will require a time source (NTP sync over the network, or manual entry via the configuration tool) to re-establish the correct date and time before time-dependent functions (schedules, logs, certificate validation, etc.) operate correctly.

**Important:** this time loss is isolated to the RTC only. The following are stored in non-volatile memory and are **not affected**, regardless of how long the unit is without power:

* Project/configuration files
* Device and parameter settings
* Cloud and MQTT credentials

**Recommendation:** ensure the miniCU has network access on restart after an extended outage so it can automatically resync via NTP. In installations without reliable internet access, the date and time should be checked and corrected manually after any power interruption longer than 3–4 days.

<table><thead><tr><th width="164">Parameter</th><th width="449">Detail</th></tr></thead><tbody><tr><td>RTC backup method</td><td>Supercapacitor (no battery)</td></tr><tr><td>RTC hold time (power off)</td><td>~3–4 days</td></tr><tr><td>Behavior beyond hold time</td><td>Date/time lost; requires NTP sync or manual re-entry on next power-up</td></tr><tr><td>Recommended action after extended outage</td><td>Ensure network access on restart for automatic NTP resync; otherwise verify/correct time manually</td></tr></tbody></table>