Article #: KA-03898
Published: 09/22/2025
Last reviewed: 09/22/2025
How To Troubleshoot a Step Down Transformer That Is Continuously Tripping Breaker
Contents
Introduction
This article will provide working instructions on how to assess and troubleshoot a step down transformer that is no longer providing output power or continuously tripping the input breakers.Purpose
The purpose of this article is to provide the end user a set of instructions to follow to assess whether the unit will require an RMA in case the troubleshooting steps do not resolve the issue.Procedure
1. First, assess whether one of the below cases are true
- The main source is connected but the transformer will not power ON. No voltage at the output
- The source is connected and powered but the fan is not functional
- The output breaker does not reset once tripped
- The input breaker has tripped
2. If the step down transformer is plugged into the UPS, yes the fan should be running. If the fan is not running, the outlets on the rear panel should still provide 120V which could be checked with a multimeter. Also, check for an obstructions of the fan. It's not recommended to use it if the fan is not working as the coil may overheat, but it's a way of telling if the fan has malfunctioned.
3. If the breakers are tripping, then take a look at the below image of the breakers. Find out if its the Input Breaker (2) tripping, or one of the Output breakers (8)
There are 4 output breakers, one for each outlet group.
4. One thing to note about the output groups too is that they're 'split' by the transformer coil.
So the manual shows:
For instance, if one of the output breakers is tripping, they may have too much of their load on Outlet banks 1 & 2 for instance.
5. Ensure the main input breaker is positioned correctly.
Troubleshooting
The questions/steps below will allow the end user to determine the situation as whole a bit better and provide clear instructions to proceed further if necessary for troubleshooting.
1. What was the model of the UPS?
2. Are there any errors on showing on the UPS?
3. Is the UPS running in Normal mode?
4. Is the UPS Outputting the correct AC Voltage (208V)?
5. Have you tried the Transformer in a different UPS outlet?
6. Are the devices plugged in to the Transformer distributed amongst the outlets (e.g. Some on Group 1, 2, 3, 4 etc.)?
If the Transformer was used via the UPS in Normal mode, the UPS would have regulated the output to the Transformer during an outage event. If it was used in Bypass mode, it's possible that a surge or large inrush could have done something to the Transformer Input breaker during an outage/multiple outages. In that case, there could be damage and would likely have to be RMA'd.
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