# Can you switch-on an UPS when the Main Supply is Off?

**URL:** <https://forumautomation.com/t/can-you-switch-on-an-ups-when-the-main-supply-is-off/13357>\
**Category:** Electrical\
**Tags:** ups\
**Created:** [July 3, 2025, 4:36pm UTC](https://forumautomation.com/t/can-you-switch-on-an-ups-when-the-main-supply-is-off/13357 "2025-07-03T16:36:05Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![TSRS](https://forumautomation.com/user_avatar/forumautomation.com/tsrs/32/8023_2.png) [@TSRS](https://forumautomation.com/u/TSRS)\
**Post date:** [July 3, 2025, 4:36pm UTC](https://forumautomation.com/t/can-you-switch-on-an-ups-when-the-main-supply-is-off/13357/1 "2025-07-03T16:36:05Z")

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**Can you switch-on an UPS when the Main Supply is Off?**

**Please anyone give me the correct answer**

 ![image](https://cdn.forumautomation.com/original/2X/8/86edfa3d1d7bcc42bb8080cc29505ed0eb12605d.jpeg)

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<div class="post-metadata">

**Author:** ![Rabert](https://forumautomation.com/user_avatar/forumautomation.com/rabert/32/6784_2.png) [@Rabert](https://forumautomation.com/u/Rabert)\
**Post date:** [July 6, 2025, 7:34am UTC](https://forumautomation.com/t/can-you-switch-on-an-ups-when-the-main-supply-is-off/13357/2 "2025-07-06T07:34:39Z")

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Yes, you can turn on a UPS when the main power is turned off, although this depends on the type of UPS & the battery condition:

- Offline (or) Standby UPS
- Online or Double-Conversion UPS

### Offline (or) Standby UPS

Normally turns off until the mains fails.

Can turn on from batteries, only if:

- The battery is fully charged.
- The UPS includes a cold start option (manual startup without mains power).

### Online or Double-Conversion UPS

- Uses an inverter to operate even when connected to the mains.
- If the cold start capability is present, the vehicle can be started directly from the battery.

### Important Condition

- The battery must be sufficiently charged to support the load.
- The Cold Start Feature is required to turn on the UPS without a mains supply.
- Not all UPS models offer cold start; consult the user handbook or specifications.

Yes, you can use a UPS without a mains supply if it enables cold start & the battery is in good condition.

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