Otago Polytechnic
electric Cod

Lindon Keith's research project confirmed that imported multiboxes can overheat even when not overloaded.

The New Zealand Fire Service was aware that multiboxes (Electrical Portable Outlet Devices) can be a cause of electrical fires. Sometimes this was because they had been overloaded, but that did not appear to be the case always. They wanted to know whether multiboxes could be a fire risk even when not overloaded.

Electrical engineering student Lindon Keith undertook evaluation of multibox reliability as his research project. A selection of brands available for purchase in New Zealand were used, including one New Zealand made brand and other brands that had been manufactured overseas. Lindon tested the boards at 90%, 100%, 110% and 120% of their rated capacity. All were reliable in overload protection performance, but he found that every brand except that made in New Zealand could overheat in time, even when not overloaded. This was due to the entire current having to pass through a very small surface area.  

Further research is required now to identify the extent of the problem. What proportion of multiboxes in each brand are at risk of overheating? And how long would it take for them to overheat? That information will help the Fire Service to decide whether there is a need to set a minimum safety standard for multiboxes sold in New Zealand.

June 2018