Piggyback Fuse Holders SAFE OR NOT?

A Bench Test Demo

I've often made use of piggyback fuse holders in auto electrical projects but I've received many questions about their safety:

• Can they be fitted the wrong way?
• Can they blow existing fuses?
• Do they draw an imbalance of current from original fuses?
• Must they never exceed a certain rating?

So I decided to perform a bench / safety test to answer these and other questions.

My tests, which you can view in this video, were fairly comprehensive. Personally I was satisfied that they were perfectly safe to use, as long as good common sense was employed. Yes it is possible to cause an overload, but this can easily be avoided with a little knowledge, as explained here.

Surprisingly I also found that it WAS possible to install a Piggyback fuse holder the wrong way round. However I did not conclude that this was in any way unsafe - it didn't create imbalances, circumvent fuses, etc - it simply caused a slight inconvenience that's easier shown than explained. So this is one of those rare occasions when I suggest you watch the video.