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How do I hardwire 10kva and 20kva transformers in a 208/120 or 240/120 environment

Implementing a hardwire stepdown transformer in a 208v or 240v environment

Product Line:

Smart-UPS / Symmetra


APTF10KT01, APTF10KW01, and APTF20KW01, All Serial Numbers


Unbalanced UPS outputs require a stepdown transformer to power 120v loads


This document refers to installing  the APTF10KT01, APTF10KW01, and APTF20KW01 transformers in a North American 120/240 or 120/208 environment. For installations in other regions please consult the users manual.

The wiring block outputs are as follows:

For domestic use, make sure that the Terminal Block Jumper is installed between the Ground Terminal and Terminal 8 on the output wiring block, as illustrated on page 8 of the user manual. Please also make sure that the input voltage switch is in the correct position.

The step-down transformer provides 240/120 output as 2 120v hots, a neutral, and a ground. It provides 208v output as a 120v hot, an 88v hot, and a ground. The 120v hot (terminal  7) and the 88v hot (terminal 9) are 180 degrees out of phase. You will measure 208v from terminals 7 to 9. The step-down transformer is not able to provide 2 120v hots that are 120 degrees out of phase as you would see with utility power.

 Note: If your installation requires both 208v and 120v output power you will need 2 separate subpanels: a 240v/120v panel and a dedicated 208v subpanel.

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