External Automatic Transfer Switch (ATS) for Backup Load Protection

Solis Integrated Manual Bypass Switch 

The Solis S6-EH1P(3.8-11.4)K-H-US high voltage hybrid inverter series is equipped with an integrated manual bypass switch. When the inverter has an alarm or malfunctions, the backup side of the inverter shuts off. This means that any load connected to the backup side will lose power, even when the grid is available. Turning the manual bypass switch on the side of the inverter from “inverter” position to “bypass” position can restore power to the loads on the backup side by connecting the grid to backup. The normal position of the switch is “inverter” which allows the inverter to keep the backup side energized during a power outage. However, if the inverter has a problem while the switch is set to “inverter” position, the backup loads will lose power until the problem is resolved or the bypass switch is turned to “bypass” position. 

External Automatic Transfer Switch (ATS) for Backup Load Protection

Because the switch is manual and requires someone to physically change the position from “inverter” to “bypass” there may be some cases where an external automatic transfer switch needs to be installed because the loads connected to the backup side are critical and must remain energized under all circumstances. 

It is possible to install an external ATS to ensure that the loads on the backup side of the inverter will automatically receive power from the grid should the inverter fail or have an alarm that shuts it down. 

Installing the External ATS

The diagram below depicts how the external ATS should be installed within the system.

1. Connect the “normal” terminals of the external ATS to the Backup ports of the inverter

2. Install double lugs in the “emergency” terminals of the external ATS.

3. Connect one set of cables from the “emergency” terminals of the external ATS double lug to the grid. This will most likely be a 2-pole circuit breaker within the main service panel that is not backed up when the grid fails.

4. Connect a second set of cables from the “emergency” terminals of the external ATS double lug to the Grid ports of the inverter.

5. Connect the “load” terminals of the external ATS to the backup distribution load panel (subpanel).

When the inverter fails, the backup side will shut off. The external ATS will sense the loss of power on the “normal” ports and will automatically switch the load connection to “emergency”, which is the grid in this case. 

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