Switches: Design Considerations
Shock and Vibration
If switches are likely to be subjected to shock or vibration, select models with the highest available actuating force. Burgess switches feature low mass mechanisms which are inherently resistant to shock and vibration.
If possible, the switches should be mounted so that the line of acceleration is at right angles to the travel of the plunger. The maximum available overtravel should be used.
Direct current (DC) ratings where shown should not be exceeded if destructive arcing and contact welding are to be avoided.
Some form of arc suppression is recommended when switches are used in DC circuits containing inductive devices wired in series with the switch and the supply.
Because of the very high inrush currents associated with incandescent lamps, applications should be subject to individual assessment.
Capacitive Loads (including fluorescent lamps)
These can generate very high peak currents which can cause contact welding. Applications should be subject to individual assessment.
The general ratings tables included in this catalog provide data for switches used to control inductive circuits at a power factor of 0.5 (EN 0.6; UL 0,7 means HP-Rating 0,5).
The majority of our switches have or will be tested in accordance with the international standard IEC 61058-1 and derived to the national standards EN 61058-1 and UL 61058-1. The new standard is designed to keep pace with industry innovations whereby the Johnson Electric transition plan ensures a smooth process to the new requirements for our customers. Approval marks specified in series or product overviews are product related, the exact approval marks are specified on our technical drawings.
Where these are not available, a general rating is given based upon in-house laboratory testing. The ratings tables should be considered as safe working maximums for most applications. However, switch performance is influenced by a variety of factors, including:
- Frequency of operation
- Type of load
- Amount of travel used
Please do not hesitate to contact Burgess about your specific application.
Electrical Life - the electrical life data contained in this catalog is based on laboratory controlled tests. In practice, frequency and speed of operation, type of load, suppression,actuator travel used, ambient humidity and temperature and other environmental conditions can have a major effect on switch life.
Individual assessments for specific applications are possible and can be undertaken by Burgess on request. Please ask Burgess if you would like an assessment for your specific application.
Mechanical Life - the figures quoted relate to the number of switching cycles made without an electrical load.
The protection classes of Burgess switches are in accordance with IEC 529 and are covered by just four codes.
Adequate protection against solids such as probing fingers and small wires>1mm. Liquids however can gain access and, unless externally protected, the switches should be mounted in dry or well-sheltered positions.
Good protection against solid foreign bodies, including dust and water splashing against the enclosure from any direction.Switches may be used out of doors if sheltered from the worst of the elements or on factory machines subjected to normal washing down procedures.
Complete protection against solids, including dust, and against low pressure jets of water from all directions.
Complete protection against solids including dust and against immersion in water at a specific pressure for a specified time. We reserve this code for switches which are factory sealed and tested.Switches should not be immersed in any liquid.
*International IK code indicates protection against mechanical impact regarding to EN 50102.
For details of the working temperatures applicable to individual types, refer to the appropriate specification sheet. Special versions suitable for temperatures outsidethese ranges may be possible. Please contact us for information.
All quoted temperatures assume stable operation. They do not imply an ability to withstand excessive cycling within the range.
Silver and silver alloys are the primary contact materials used in Johnson Electric switches.
Gold contacts should be specified when switches are to be used in low voltage control or logic circuits, especially when long periods of inactivity are expected or when atmospheres with a high sulphur content may be encountered.
Gold contacts are generally available in two forms; gold plated silver alloy contacts, which can also be used at higher currents or gold alloy cross-point contacts, which are only suitable for switching low currents.
The following notes are intended merely to stress the most important and general aspects of good switch installation procedure and to provide some helpful additional information. Safety Consideration Installation should only be carried out by competent personnel.
Switch Positioning and Operation
Pre-loading of the switch actuator must be avoided. The actuating medium must be able to operate the switch through the operating position into overtravel and then to retract far enough to allow the switch to regain its free position. Burgess recommends that the actuating medium should drive the switch into at least 50% of the available over-travel.All ratings tables shown in this catalog are based on the use of all the available overtravel.
Installation Recommendations (EN 61058-1)
Side mounting switches should be mounted on smooth, firm, flat surfaces using the recommended screw size. Avoid over tightening the screws. For added security, they should be locked using epoxy resin. Do not attempt to enlarge switch mounting holes and avoid over stressing the switch. Use insulating material between the switch and metallic plates to increase clearance on switches with open terminals.
When soldering, overheating of the switch insulation must be avoided. In certain circumstances, it may be advisable to use a heat shunt. For optimum mechanical strength, the conductor should be wrapped round the tip of the terminal taking care to avoid loose strands of wire. The soldering iron tip should be applied to the end of the terminal while simultaneously applying solder. Remove the iron as soon as the solder has wetted the conductor and terminal end. A-soldering iron tip temperature of 350°C (260°C/5 seconds for PCB Terminals) applied for a maximum of 2-3 seconds should be adequate.
For lead-free solder, is usually needed an iron tip temperature 15% higher.