2.21 was determining and testing alternative substances. Today MERZ products fulfil the requirements of the standard completely. We did not change the article numbers for the individual products. Starting from 1. April 2006 we certify the conformity of our products affected by that standards according to the updated version of that regulation valid from 21.10.2005. Safety switches Safety switches are encapsulated main- repair or maintenance switches where the housing cannot be opened while the handle is locked by a padlock in OFF-position. MERZ safety switches are realized with the enclosure series I1 to I3. Single-phase starter switch Single-phase starter switches are used for starting of single-phase AC-motors. There are versions available for unidirectional or bidirectional motors with and without starter capacitors. Star-Delta switches Star-Delta switches are needed to start larger three-phase alternating current motors with short circuit rotors from 4kW upwards. The public power distribution network (230V/400V) does not allow start-up current higher than 60 Amps according to the TAB regulation. Motors with a capacity rating above 4 kW are therefore subject to a current limiting start-up mode. Such method prevents fuses to blow-up and potential voltage drops caused by a very high start-up current in a direct switching mode. Star-Delta switches are offering the most compact and cost effective solution. There are versions with one or two rotating directions available. Furthermore the switches can be equipped with additional impulse mode contacts in order to activate or control additional contactors. Step switches Step switches provide the widest offering in the MERZ MN product range. The switches are available from 3 to 12 positions with and without 0-position. All switches are available in 1-, 2- or 3-pole versions. Step switches are always activating one (respective 2 or 3 for 2- or 3-pole versions) contact only while switching from one position to the next whereas this contact will be disabled once the switch is moving to the successive position. There is no overlapping from one contact to the next during the changeover phase. Switch-disconnector Switch disconnectors are mechanically operated switches in a circuit which are able to make, carry and break under normal operating conditions currents including a specified overload. In the open position the contacts fulfil the requirements of a disconnector. IEC/EN60947-1 Switches with spring-return In many applications it is necessary to control the machines and facilities by impulse or inching modes. In order to ensure that the device is not switching into constant modes MERZ has designed cam switches in such way, that the handle and the related switching contacts automatically move back into the starting position once the handle is released. Typical examples are lifts, where the switch must be held until the upward or downward movement has reached its wanted position or with pumps, that are usually operating only in one direction but may have to temporarily change directions i.e. for cleaning mode.
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