Do I Need to Fuse the Positive and Negative Sides of a 24VDC Floating Power Supply?

31 August 2021

We were asked by a customer that uses MEAN WELL power supplies in many of their products if they needed to fuse the negative output cable in a 24VDC floating power supply, and if so why?  

The customer was only fusing the positive side, but their client thought that the negative should be fused as it has voltage potential respect to earth.  

DIN rail power supply
MEAN WELL 960 WATT DIN Rail Power Supply


It is not necessary to fuse both positive and negative leads of the supply. A single fuse will break the circuit sufficiently.  

Putting a fuse in the negative rail will not really be of help as it is unlikely that both fuses will blow at the same time.  

Yes, there will be a voltage potential to earth, but this is only leakage current and is not harmful. It is less than a milliamp. Even if you put a fuse in the negative lead and this blows, the positive fuse will most likely still be intact, and the leakage current will be able to come from the positive output. 

If you have a question about using MEAN WELL power supplies, please do not hesitate to contact Power Supplies Australia