13 of 20 - Installing the Solis Autotransformer

Solis ATR Specifications:

Note: The Solis Autotransformer goes between the RHI-1P(5-10)K-HVES-5G inverter and the main service panel. It also connects directly to the backup loads sub panel. Think of the ATR as the central "hub" of the system. See the wiring diagrams found in the Installation Overview.

The Solis Energy Storage Inverter is capable of supporting a Backup (Critical) Loads Panel. The inverter generates 240V AC power with no neutral. If your supported loads accept 240V then you will be fine with no autotransformer. However, most people are going to want 120V/120V split phase with a neutral in order to energize a small sub-panel. In this case, a Solis Autotransformer is required.

! Important: Backup can be turned on or off independently of Self Consumption, Time Charging, and Off Grid Modes. This is done AFTER the installation by going to Backup Control in Advanced Settings, selecting Backup ON/OFF, highlighting ON and pressing enter. Please be warned that doing this will energize the "BL1 and BL2" terminals in the inverter with 240Vac. You should also go into Backup Settings and make sure the voltage is set to 240V and the frequency is set to 60 Hz. Please use the Up, Down, and Enter buttons to change the settings or else you will get alarm codes.  

The purpose of the Backup Control is to energize the backup loads panel. This is not to be confused with Backup mode that is one of the four energy storage operating modes. If anything is connected to the AC-Backup terminals then in order to energize it (on grid or off grid) the Backup Mode will need to be turned ON.

The maximum that the system can produce is up to 6000W of AC backup power at 25A but the system can surge to 7000W for one and a half seconds before going back to 6000W. 

The full Solis Autotransformer User Manual is attached at the bottom of this article. 


How to install the Solis Autotransformer (ATR):

  • Select a central location for the ATR that is physically between the main service panel, the inverter, and the backup loads sub panel
  • Ensure that the bracket will be secured to at least one structural stud, or concrete backing with concrete anchors
  • Mount the bracket for the ATR and follow the Installation Space Requirements below
  • Caution: the ATR is rather heavy (53 lbs) so use proper lifting techniques when handling it to avoid injuries
  • Bring the ATR in at a 15 degree or less angle and then rotate the ATR down so the hooks catch on the bracket
  • Secure the ATR with the four M4 screws provided - tighten them to 7.3-9 N.m



  • Take the ATR cover off by loosening the six screws with a Phillips screwdriver. Also, remove the three plastic plugs from the bottom of the ATR by loosening the plastic lock rings until the come off and pushing the plug out through the bottom. 
  • Run your conduit from the main panel, the inverter, and the backup loads sub panel directly into the holes and then secure them before pulling your wires through. Below is a guide on what size and color wires to pull to the ATR.



How to wire the Solis Autotransformer (ATR):

The ATR terminals will accept 8AWG and 6AWG wire. The size you need will depend on the size of your system. Please use this Wire Sizing Chart if you need help determining the best wire size. Here are recommendations for wire sizing and coloration between the various components of the system:

1. ATR to Main Service Panel AC breaker (40-60A) or AC disconnect switch

  1.     a. Line 1:   6-8 AWG black
  2.     b. Line 2:   6-8 AWG red
  3.     c. Neutral:   6-8 AWG white
  4.     d. Ground:   8-10 AWG green

2. ATR to Inverter

  1.     a. Line 1 to "AC Grid L1":   6-8 AWG black
  2.     b. Line 2 to "AC Grid L2":   6-8 AWG red
  3.     a. Line 1 to "AC Backup L1":   6-8 AWG black
  4.     b. Line 2 to "AC Backup L2":   6-8 AWG red

3. ATR to Backup Loads Subpanel supply breaker (25A)

  1.     a. Line 1:   6-8 AWG black
  2.     b. Line 2:   6-8 AWG red
  3.     c. Neutral:   6-8 AWG white
  4.     d. Ground:   8-10 AWG green

3. Main Service Panel to Backup Loads Subpanel (passes through the ATR)

  1.     a. Line 1 from critical loads breaker 1 - relocated to the Backup Loads Subpanel
  2.     b. Line 1 from critical loads breaker 2 - relocated to the Backup Loads Subpanel
  3.     c. Neutral: 10AWG  white - goes from the Main Service Panel neutral bar to the Backup Loads Subpanel neutral bar
    1. Note: this neutral is for the critical loads that are being relocated from the main panel to                      the backup loads subpanel.



How to operate the AC Bypass Switch of the ATR

The switch has three settings: 1, 0, and 2

Setting 1 is normal operation mode, the backup loads will get its energy from the inverter

Setting 0 deenergizes the ATR, this is essentially turning it off

Setting 2 is the "bypass" meaning the backup loads will get its energy from the grid directly and not from the inverter


Note: If the inverter goes into a fault and shuts down, it is best to immediately switch from 1 to 2 to make sure that the backup loads panel remains energized. Once the fault has been resolved or the inverter replaced, switch back over to 1




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