When a thermostat or similar switch "closes" to operate a circuit, that sends voltage, typically 24VAC through the coil assembly. Items are of course not shown to relative scale. When the thermostat is not calling for heat the low voltage switch in the thermostat is in the Open position and the circuit is not energized. In our sketch above we've simplified a schematic of the operation of an electrical relay, in this case we illustrate a circulator relay control used to control the circulator pump of a hot water heating system. In our image of a Honeywell brand relay control (earlier on this page) you can see the magnetic coil - those red-copper windings are part of the coil assembly. So we use the little low-voltage, low-current switch (such as a wall thermostat) to operate a contactor or relay that in turn operates the higher current circuit.Ĭurrent through the electromagnetic coil in the relay operates a magnet in the relay (pink rectangle in the illustration) that in turn mechanically closes electrical contacts (blue) that are designed and rated to handle the voltage and current of the device being operated. Pump control switches are described separatelyĪ low voltage switch such as a wall thermostat used to turn heat or air conditioning on and off operates at 24VAC, at very low current (Amps), and cannot handle the switching of higher voltage (120V or 240V) to higher-current-using mechanical systems that might run at 20 to 40 Amps.The low-voltage 18-gauge wiring and the little "switch" in the thermostat would burn or melt at those higher currents. In this case water pressure pushing on a spring-operated diaphragm mechanically operates or moves the relay contacts to close or open the switch to turn on or off the water pump. To permit another external force or condition a heavier duty higher-voltage piece of equipment (like an water pump).Thermostats used to control heating & cooling equipment are described separately That thermostat switch, powered by a low-voltage thermostat wiring (18-gauge) circuit (24VAC), operates a physically separate relay switch or "contactor switch" (located in the heater or air conditioner) that turns on or off a heavier-use wiring (14, 12 or higher gauge) circuit wiring a higher voltage (120VAC or 240VAC) that in turn will operate the air conditioner or heat pump. In this case the thermostat, in response to room temperature, changing temperature moves or operates a low-voltage switch inside the thermostat. To permit using a light-duty low-voltage switch (like a thermostat) to operate a heavier duty higher-voltage piece of equipment (like an air conditioner).There are several reasons that these controls are used: The relay is basically an on-off switch that uses a lower current circuit to switch on or off a higher current electrical circuit (and thus device). In typical mechanical systems used in buildings, such as air conditioners, heat pumps, electric heat, and water pumps, one or more electromagnetic relays are used to control the operation of these devices. (Roberts 2006, copy available at REFERENCES) In response to it being energized or de-energized by that or If you hear buzzing or chattering at this relay it probably needs replacement.Īn electrical relay is a device that changes the state of a circuit Shown here: A typical general-purpose relay switch or contactor produced by Honeywell. What is a Relay or Contactor Switch, How do They Work & Why Are They Used? A/C CONDENSER CHATTER / BUZZ REPAIR SUCCESS.WATER PUMP CONTROL SWITCH CHATTER or BOUNCE.HEAT or ELECTRIC HEAT CONTACTOR SWITCH CHATTER. ![]() ![]() AIR CONDITIONER / HEAT PUMP RELAY SWITCH CONTACTOR CHATTERING.CONTACTOR REPAIR, CLEANING POINTS - temporary repair success.Clicking or chattering electrical relay switches Article Contents We also provide an ARTICLE INDEX for this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need. Shown at page top: the relay switch in a water pump pressure control switch. Control relays are also used to control water pumps in private well systems or in water pressure booster systems. Relays are used to switch on or off backup heat for heat pump systems. Relay switches are widely used to control equipment found in or on buildings including air conditioning system or heat pump compressor/condenser unit compressor motors, fans, and in an air handler the blower fan used in forced air heating and air conditioning systems. This article explain control relay switch chattering or rapid, repeated clicking noises, their cause, meaning, and repair. We have no relationship with advertisers, products, or services discussed at this website.Ĭontrol relay switch chattering noises might also be described as buzzing, clicking, clicking, humming sounds. ![]() InspectAPedia tolerates no conflicts of interest.
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