Other Switches and Relays
Other switches and relays used in heating and/or cooling systems include the following:
• Balancing relays
• Manual switches
• Auxiliary switches
A balancing relay (see Figure 6-45) is used with an electric motor that does not have an integral balancing relay. The relay is mounted separately from the motor so that vibrations will not affect it.
A manual switch is used to manually perform one or more operations in a heating and/or cooling installation. These switches are generally two-position types (on-off), although multiple-position switches are also available. An example of the latter would be the heat-off-cool switch on a heating and cooling thermostat. Examples of some special switching hookups in which manual switches are used are shown in Figures 6-46, 6-47, and 6-48. In each of these examples, a relay could have been used instead of the manual switch.
An auxiliary switch (see Figure 6-49) is used in conjunction with an electric motor to provide control of auxiliary equipment. This control functions as a direct extension of motor operation. The auxiliary switch may be an integral part of the motor or an external unit fitted to the motor and adjusted to open or close at the desired point in the motor stroke (see Figure 6-50). As shown in Figure 6-51, the internal auxiliary switches are in a single-pole, double-throw (SPDT) configuration.