Where do I start? Two years ago, in the course of my job, I was testing some plugboxes on the school’s PAT tester, and one failed with an earth continuity problem. And it turned out, the plugbox, which carried the HPM brandname, was so poorly designed that the earth contacts became bent on plug insertion and therefore contact was unreliable. After years of doing this testing, these particular type of plugboxes, this particular model and not other models of the same brand, always failed the test and we had to ditch them. So I talked to Energy Safety Service, part of the Ministry of Economic Development. And they said “We can do nothing”. My extrapolation from what they are saying is that there is nothing in the electrical safety standards and certifications for plugboxes that requires them to be designed for an endurance of any particular number of insertion cycles. In the computer industry, insertion cycles are quite commonly found in standards for computer connectors like USB and hard disk plugs and sockets. What is standard in our industry, worldwide, for some unfathomable reason cannot be put into such a basic piece of electrical equipment as a plugbox in its design requirement.
Now fast forward to this week. I bought a couple of heaters, and I ended up with questions about the electrical standards for these. Most people in the electricity industry know about Class 1 and Class 2 appliances; I know about them because I have to test them as separate processes on a PAT tester. Class 1 is an earthed appliance, which is quite common for devices with a metal case, because it can be tricky for the metal to be insulated from any electrically live parts inside an appliance. This is especially true of heaters, because metal is often the only material that can withstand the heat of operation. Class 2 is a double insulated appliance, and for a heater this is generally a plastic body, which is usually a fan heater, because the airflow carries the heat away and prevents it building up, and because often enough inside that plastic body is some metal such as the grill and element supports which help contain the heat inside the body and prevent it melting.
So it was a great surprise to me to find that De Longhi has started to produce a line of convection heaters, metal bodied, which are labelled “double insulated” and have only a two wire cord. As you will see in the picture below, what is the difference between one of these heaters and a cheap clone, which just happens to have a three wire cord and an earth terminal on the body?
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| Clone | De Longhi |
You can see that the clone has a terminal, and there is a wire going to it on the inside. The De Longhi has the hole for the terminal, but no wire. Those wires you can see in the right hand picture are all carrying mains current, and they go onto spade terminals which are generally exposed. In addition, the heating element on these types of heaters, like fan heaters, is generally uninsulated wire. Once again the Energy Safety Service have been helpful in explaining that, these days, double insulation means air can be used as an insulator. So there is no innate requirement for that metal chassis to be earthed, if all the live parts are insulated by enough air from the chassis. So what’s the hitch? Well, wires can break or come loose and end up touching that metal chassis, or if the chassis became bent it could touch the element – and that’s why traditionally, metal bodied heaters have been earthed and in most cases still are. I was in another shop today and had a look at a lot of metal heaters. All the De Longhi convectors were “double insulated” and all the other various brands were earthed, including the ones that were obviously very similar, maybe copied from a De Longhi design. Yet, they are all the same basic design, almost identical inside.
Who decides these standards? They are international so they are not decided in NZ and I expect that because of some treaty that in NZ no ordinary citizen gets any input into them. Heaters are classified as a High Risk item and therefore more rules apply, but these rules appear to rely on a manufacturer providing the correct documentation. Once again there don’t appear to be any standards for the way these heaters are designed, just some vague expectation that they are supposed to meet a standard but not how that is achieved.
The big picture doesn’t stop at electrical safety standards. It goes on into any standard for anything that is traded in New Zealand. Our governments negotiate and enter into international treaties which do their best to wipe out any restrictions such as minimum standards. In a case such as these we are talking about a few cents difference in the manufacturing cost. Does that translate into a lower price for the consumer? I doubt that very much. The few cents over hundreds or thousands or tens or hundreds of thousands of appliances, adds up to a significant difference in profit for the manufacturer. Does that trickle down back into the local community? That I also doubt greatly. Food for thought…
