The Power Protection Blog

I recently had a question regarding the surge energy rating of our MiniGuard UPS systems. The answer is 320J, but got me thinking why anybody would want to know that. So I’ve had a brief scour of the surge suppression devices, with many boldly advertising their huge surge energy capabilities into the thousands of Joules. So the theory is, the higher the surge energy rating the better the device is.

How ludicrous this is, and I’m here to put the record straight. The energy rating of your surge suppression has zero effect on how good this will protect your equipment when a surge hits it. A small surge suppression device will be just as good as a large device for 99.99%* of the transients it’s ever likely to experience, and for the 0.001% of the time you are hit with a large surge as the result of a localised lightning strike, then both surge suppressors will probably fry anyway.

Another thing you should be aware of, is that even though surge suppressor may divert hundreds if not thousands of Amperes of surge current away from your equipment (reading one spec states 40,000Amps, but doesn’t tell you it is only for micro Seconds – that is a few millionths of a second), they will still let hundreds of volts through to your equipment. And guess what? Most of the time it is this kind of let through that will damage your equipment, and it will leave no trace. You will just put it down to random equipment failure. If you’ve fallen for one of these “if your equipment is damaged when using one of our products we will pay for it” guarantees, you will see in the small print that the equipment must have physical signs of damage, or if it doesn’t say this directly, the manufacturer will want to inspect the equipment for such signs before they pay out anything.

So, are surge suppressors a waste of time? Not at all, they provide a useful function in removing the peaks and a lot of energy from large impulses, but these alone will not stop damage to your connected equipment. You need secondary lines of defence, such as filters and/or isolation transformers to really protect your equipment.

*Well Vic Reeves said 88.2% of statistics were made up on the spot, and he’s probably right. This data doesn’t really exist but obtained by careful conservative consideration.