Change In USA Standard Affects Main Switch!
Requirement for "deliberate action".

Moeller has added special main switch assembly kits each with a supplementary handle to its already extensive range of door coupling handles to meet USA requirements for main switches with rotary drives. This combination of two special handles meets the requirement for "deliberate action" when releasing the door interlock and when switching on the main switch with the switch cabinet door opened. A technical report provides extensive information on this very important issue. Existing customers simply have to replace the previous main switch assembly kit with the new solution. Moeller can help new customers with the conversion to main switches that offer additional features for exports to North America such as approved current limitation for increasing the short circuit current rating (SCCR) of the entire system.

It has long been a requirement for main switches, irrespective of the position of the switch cabinet door, to be accessible for operation and lockable, and the switch position must be clearly indicated at all times. It was always necessary for the locking of switch cabinet doors to be dependent on the switching state of the main switch or switches. Two simple rules apply: It must only be possible to switch on the main switch of a switch cabinet if all switch cabinet doors are closed and conversely it must only be possible to open switch cabinet doors if the lockable main switch is switched off.

Faults are often not found until the system can be inspected in the On position in an energized state. This applies also in part to parameter adjustments which are only possible during operation. These requirements are taken into account by the North American regulations. These allow a temporary overriding of the mechanical and/or electrical interlocks between the main switch(es) and the switch cabinet door(s), even in an energized state, by an experienced and skilled person using a tool. If you wish to switch on the main switch when the switch cabinet door is open, higher requirements apply that are comparable with the child-proof cap on a medicine bottle.

UL have confirmed that the new "Supplementary Handle" meets the latest USA requirements (Figure 1). The handle mounted on the switch shaft in the switching cabinet was designed so that unskilled persons cannot switch on the switch accidentally or unintentionally, but only in combination with several operating steps which enable the main switch to be operated.

The handle must first of all be rotated by approx. 20° in the ON direction. In this position, the handle must be pushed in towards the switch and then moved through the remaining angle of rotation whilst keeping it pressed at the same time. If the handle is not pushed in at the 20° position, it can be rotated to the end stop without operating the switch. No special knowledge and measures are required for off switching. UL has stipulated the provision of an additional warning plate on the switch, which indicates that it should only be operated by skilled persons.

The North American standards do not allow electricians to carry special accessories for the switch operation. The accessories for the actuation and the locking facility must therefore always be permanently connected to the switch and must not be detachable. Moeller offers complete main switch assembly kits that are fitted on switches with toggle actuation. The kits enable the switch to be locked with the electrician's padlocks. They include an extension shaft that can be adapted to the depth of the switch and a door coupling handle for mounting in the cabinet door. The switch position is also clearly distinguishable when the switch cabinet door is opened. The kits are available with black or red and yellow handles.

Moeller GmbH, 53105 Bonn
Tel.: +49 (0)228 602-0
Fax: +49 (0)228 602-2275
E-Mail: presse@moeller.net
Internet: www.moeller.net
Please direct your enquiries to:
Corporate Communications, Tel.: +49 (0)228 602-2915

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