Why Do I Keep Getting Shocks Off My Gear?
We get a lot of calls from people saying they want to bring their gear in because they’re getting annoying but minor electric shocks off it. We even had someone ring last week because they had moved their DJ gear to the garage and were continually getting shocks. They even got an electrician in to test everything and they couldn’t resolve the issue as a standard PAT Test and Tag assessment showed no issues.
Now, there is a not so freaky reason this can happen BUT we always err on the side of caution and advise to bring the gear in for an electrical safety test. We would hate for your case to be that one time when there was actually something wrong right?
So Why Does It Happen?
There are two protection classes of electrical appliances used in Australia and NZ as defined by IEC 61140 which stipulates the protective-earth connection requirement of devices.
Class I is where the unit has a three pin power plug – active, neutral and an earth or ground connection.
When you use Class I equipment the chassis of the unit is directly connected to electrical earth or ground. Any electrical failure within the appliance can never cause the chassis or body of the unit to induce electric shock. You and the equipment are at the same potential or voltage at all times so everything around you will also be at that potential.. everyone is safe and happy with no zaps.
Now, there is also Class II.
Class II is where the unit only has a 2 pin plug – active and neutral.
Due to internal capacitances usually from radio frequency emission reduction circuits, a small AC current can be passed to the metal chassis. These currents are harmless to humans as they are way down in the micro amp ranges BUT they can charge the metal chassis up to 100 or more volts at times. If you are “grounded” and touch the chassis or a socket or connected lead etc you will feel a small tingle as you discharge the chassis to the same potential/voltage as you.
Class II appliances are also known as Double Insulated because there is a requirement that no single failure can result is the chassis becoming live so they use reinforced or double layers of insulation where necessary. A failure in Class II equipment where the mains active comes into contact with the chassis could easily be fatal. Please note, we are legally required to report any poorly executed repairs we observe or any claim of electrical shock.
So How Can We Avoid It?
It is very common these days for consumer audio and DJ gear to have an IEC C7/C8 (Figure 8) or IEC C17/C18 power connections. These are obviously 2 wire connections so therefore Class II and we know what that means now right?
In a simple DJ set-up for example, you might have a pair of CD/Media players and a DJ mixer running into a pair of powered speaker monitors. Imagine for a second that all these items are Class II. Yep. It is very likely that each time you touch something metallic on one of the items or connecting leads you will get that little zap as you and the chassis become one with each other.
It is hoped that at least one item in a set-up is Class I so the audio connecting cables will hold the chassis of the other attached equipment at our desired ground potential so no zaps are in store for you.
In the case of none of your gear being Class I then we can supply you a grounding plug that will plug into your power board and the single ground wire coming from it you attach to the mixers ground screw.. problem elegantly solved. Contact us for more info.
PLEASE! As I mentioned above, anyone that receives a shock off any gear for any reason should get it to us asap to be electrically safety tested. No exceptions.