Ellis urges cleat test caution

Sept 2011

Leading cable cleat manufacturer, Ellis Patents has issued a stark warning that incorrect interpretation of short-circuit test reports is leading to inappropriate cleats being inadvertently specified and installed - a situation that is putting vital electrical installations and lives at unnecessary risk.

The issue, according to the UK company's managing director, Richard Shaw is that the headline figure reported on third party test reports is frequently, and mistakenly, taken to mean that the products tested deliver the same level of short-circuit withstand irrespective of the installation.

"You cannot say that a specific cable cleat has a short-circuit withstand of 150kA without qualifying the statement," said Richard. "For example, you'd need to say that the cleat has a short-circuit withstand of 150kA when securing 43mm cable in trefoil at 300mm centres."

Shaw highlights a recent report that showed a product withstanding a peak short-circuit of 138kA, but that on full reading it became clear that the test rig was set up with four trefoil circuits in parallel and that, under these circumstances, whilst the overall fault level was 138kA, each of the four trefoil groups only saw a quarter of the fault, equivalent to 34.5kA.

"It's easy to see how this report could have been misinterpreted and the product taken to be much stronger than it really was," he said.

"This example is just one of many, but it clearly highlights the need for third party test reports to be carefully analysed. Of course the onus is on the specifier or contractor to do this, but as a leading manufacturer we are more than happy to offer advice."

In order to correctly interpret a report, Shaw suggests that those with specification responsibility should firstly ask two simple questions. Firstly, is the product tested the same as the product being offered? And secondly, is the test installation similar to the project installation? For example, a test of three single conductor cables in parallel secured with single cable cleats cannot be compared with a trefoil installation secured with trefoil cleats.

He goes on to say that there is only one safe way to interpret a report and that is by calculating the forces experienced by the cleat during the test and comparing it with the anticipated force the nominated cleat would see in the proposed installation.

"The moral of the story is clear - don't judge a short circuit test report by its cover," he adds. "Instead, make absolutely certain that the cleat you're specifying is suitable for the specific installation and if that means asking for project specific testing then so be it."

Ellis Patents prides itself on the extensive third party testing it puts all of its products through prior to taking them to market and the fact that they will always agree to project specific testing to secure an order. ENDS

Client: Ellis Patents