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Why it's hip to be square

Here at Hager we prefer square knockouts for our consumer units. David Evans found out why...
One of the heated debates amongst the electrical manufacturing community at the moment is the choice between square and round knockouts.

In this heated debate, where does Hager stand?

We believe that square knockouts provide the best solution when installing a consumer unit in a residential application. Square knockouts have been fitted to help make installations simpler, if not easier, than previous consumer units.

What else makes square knockouts the perfect choice compared to round? We spoke to Steve York, Residential Market Manager for Hager, to provide some more insight on this subject.

1.Cable management that is utilised in residential applications tend to be plastic mini trunking. By positioning the rectangular knockouts at the back of the board, this aligns the position of the trunking to suit 50mm x 50mm trunking on the top face of the board for a single knockout and 50mm x 100mm when two of the large knockouts are removed.

2. A rectangular knockout allows a significant number of cables to be installed through a single entry point. Helping your install to be quicker and easier on site, allowing your time to be spent on more time consuming parts of the installation.

3. A grommet strip is provided with all Hager boards to protect cables from any sharp edges left by the removal of a knockout. Cables should be protected from cuts and abrasions where they pass through a metal enclosure.

You can buy further grommet strips as a 5 meter pack here.

4. The IP rating on the top edge of the board (IP4X) can easily be achieved by butting trunking up to the consumer unit or running a length of trunking across the top of the consumer unit.

As long as the cables entering the board are protected from any sharp edges there is no specific requirement for any fire proof or intumescent gland to be fitted. IP4X requires that a 1mm diameter probe is not able to enter the enclosure. All other surfaces of the consumer need to comply with IP2XC when installed.

5. Small rectangular knockouts are provided for the entry of meter tails. These knockouts allow the entry of 2 x 25mm² insulated and sheathed meter tails along with a 16mm² CPC.

If you’re using the knockout on the top surface, we advise the use of 40mm x 25mm trunking to achieve the IP4X.
Steve York explains further why at Hager square knockouts are preferred to round:

“When designing the metal consumer unit, we spoke with our customers about how they bring cables into the boards. In residential applications the installers wanted to carry on using mini trunking, so we decided to place rectangular knockouts situated at the rear of the board to facilitate this type of installation.”

As part of our Mythbreakers series we discuss the role of glanding, Intumescent seals and trunking in containing a fire in relation to amendment 3, a myth which is linked to the use of plastic trunking and rectangular knockouts.

Watch the video below.
Do you have a question regarding square v round knockouts? Feel free to post them to us on Twitter and join the debate.
Author: David Evans
Posted: 29th July 2016
Get in contact: info@hager.co.uk | Twitter