It’s an area that seems to cause a great deal of confusion – whether or not to test SPDs? The British Standards, in this case BS7671, do not mention anything about the testing of SPDs and neither does the lightning standard BS EN 62305. What the latter does say is that SPDs might be tested at the same time the lightning protection system is being tested or after a suspected lightning strike. That would seem to make sense.

So, does this mean that SPDs do not need testing? Yes, basically there is very little purpose in doing so. 

Firstly, the SPD, according to the product standard family BS EN 61643, is meant to display the device’s status, either healthy or defective. How this is shown on the device can vary depending on the brand, but the SPD needs to be able to show that it has failed. For example, if we take the DEHN power SPDs in the Redline range, the device status is shown via a green is good to red is defective display indicator on the front of the unit.

Let’s not forget that the SPD is a binary device -  it either works or it does not, and it will display this.

Test function

Some multi-meter manufacturers promote an SPD test function, but we would suggest steering away from any SPD test regime due to its limited value to the end client beyond the value of an “audited” walk around inspecting the SPDs and this is what the clause in BS EN 62305 is all about.

In fact, even DEHN  produces a test device for the products. It is reassuringly expensive, we don’t mind admitting, and it tells you what you already know that the SPD is okay or not. We are happy to supply the device if you want one.

Perhaps most importantly, the reason we don’t promote testing, or even our tester, is that the test is only valid the moment of the test. It has very little utility or value beyond that.

Condition monitoring

All the issues about testing  disappear if an SPD with a volt-free remote changeover contact is used. This is because by using this permanent condition monitoring function you get a valuable tool in gauging the state of play, whatever the size of the installation.

Only with constant condition monitoring can you know when an SPD has failed and then act upon that information. No test regime can replace this. For this reason, we at DEHN do not support test regimes. There are fundamental limitations present in annual testing and there is also the creation of a false sense of security.

And here‘s a final thought for those site operators or owners being approached by companies that are offering SPD testing. It is not mandated in any standard; inspection alone is mentioned but permanent or constant condition monitoring is the best way forwards. This can be achieved by many means from a simple accessible lamp or alarm or a signal fed into a BMS contact.

If you want to know more or discuss an installation, please get in touch.

Simply give us a call on 0113 541 8921 or email [email protected]