What is the most common temperature sensing element used for mechanical thermostats? What is the switching action of a fan cycling head pressure control? The coil voltage, number of contacts, and the contact voltage and amp ratings, A system that controls loads by opening and closing electrically operated mechanical switches is described as, When the contacts on a contactor or motor starter begin to stick, out and cut-in points of a control is known as, The difference between an SCR and a TRIAC is that, a TRIAC can switch AC current but an SCR can only switch DC current, If the contacts on a starter become pitted, they should be, Compared to relay logic systems, solid state logic systems. The oil safety control is a differential pressure switch and operates on what two pressures? A technician checks the coil of a relay with his ohmmeter, and the reading on the scale is infinity. it provides a time delay for starting motor loads. Which of the following methods are used to ensure snap action of low voltage thermostat elements? residential air conditioning control systems. Contactor can handle more current than relays, Overloads are designed to protect against. What is the cut out? Know your limits. Breaks the circuit to the coil of the contactor controlling the motor. What information must be used to select the proper contactor in order for it to function as designed? Which of the following are two main types of thermostats? The transformer in a heating or cooling system provides the low-voltage power source for the control circuit. If you have suggestions or comments they are welcome. In a remote bulb thermostat, as the temperature of the ____________________ changes, as will the pressure exerted on the diaphragm. Regulate temperature of liquids or air in a variety of applications. Line voltage thermostats normally operate on. How does a remote bulb thermostat work? In a remote bulb thermostat, the pressure exerted by the diaphragm on the mechanical linkage will open and close a set of _____. The purpose of an electrical overload device is to protect against, Compared to mechanical thermostats, digital thermostats, A control which responds to changes in pressure is called a. This component uses the properties of AC induction to step up or step down voltage for particular HVAC applications: What is the first step a technician should take when testing or changing out a capacitor? contacts The transformer for a residential unit is used to convert line voltage to 24 volts. Low voltage thermostats normally operate on. This electrical component allows current to flow in only one direction, and operates similar to a check valve: energized with a shorting probe because they can store a residual electrical charge. What is the common sensing element used in an electronic thermostat? When a pilot duty overload protecting a motor detects an overload, it? The difference between a relay and a contactor is that? When will current flow through normally open (NO) relay contacts? What mode of operation does the letter R designate or represent in a low voltage thermostat? A system that uses electronic components with no moving parts can be described as. This indicates what condition of the coil? Some commercial and industrial high-voltage equipment uses transformers that drop the line voltage to 240 or 120 volts. mercury bulbs and small permanent magnets. Overloads sense current by converting it to, The difference between the minimum and the maximum operating points within which a control will function accurately is known as. Standard Remote Bulb Controllers. What mode of operation does the letter Y designate or represent in a low voltage thermostat? An electrical component that stores energy when an electric charge is forced onto its plates is called a: What device can best be described as an electrically operated switch? The ____________________ thermostat is commonly used to control the temperature of any medium, whether liquid or vapor, in many applications. In a remote bulb thermostat, the pressure exerted by the diaphragm on the mechanical linkage will open and close a set of ____________________. This one explains how the mechanical bulb type thermostat operates. Which type of thermostats provide the closest temperature control? Most residential and small commercial installations use a 12-volt control system. What is the maximum safe secondary current for a 40 VA transformer that has a primary voltage of 240 V and a secondary voltage of 24 V? The transformer has two windings, the _______ and secondary. The temperature in any structure, regardless of its age, location, or design, can be maintained at comfortable levels with a(n) ____________________. Used to regulate temperature of air or liquids in ducts, pipes, tanks and boilers; Suitable for applications requiring temperature control of air or liquids where controller must be placed outside the sensing area; The bimetal thermostat derives its name from the fact that it uses three similar metals. What mode of operation does the letter G designate or represent in a low voltage thermostat? -Capacitors. A motor starter has built in overload protection, Pressure in the bulb rises and falls with temperature. Low voltage thermostats would be used for which of the following applications? This one explains how the mechanical bulb type thermostat operates. because solid dtate logic systems operate faster, use less power, and can control more functions. The ____________________ element of a thermostat is the part that moves when a change in temperature is sensed. A close on rise pressure switch has a cut in of 50 psi and a differential of 15. The ____________________ thermostat is used on control systems with a 24-volt supply. If you are a homeowner looking to repair your own appliance, understand that the voltages can be lethal, the fuels are highly flammable and high pressures are used. ____________________ are stationary inductive devices that transfer electric energy from one circuit to another by induction. When will current flow through normally closed(NC) relay contacts? What is the difference between a contactor and a motor starter? Transformers are rated by their primary voltage, secondary voltage, and volt-amperes (VA). A heating thermostat closes on a(n) ____________________ in temperature. When ohming the windings of a 24 volt control transformer, the primary winding should have a higher resistance than the secondary winding, The purpose of a standard control transformer is to, Reduce line voltage to 24 volts for HVACR control systems, By melting when excessive current flows through it, opening the circuit. Pressure in the bulb rises and falls with temperature What information must be used to select the proper contactor in order for it to function as designed? This video is part of the heating and cooling series of training videos made to accompany my websites: www.graycoolingman.com and www.grayfurnaceman.com to pass on what I have learned in many years of service and repair. Bleed the residual charge, preferably using a 2 watt 20k ohm bleed resistor. The difference between a line voltage and a low-voltage thermostat is in the size of the bimetal element. Why are manufacturers replacing relay logic systems with solid state logic systems? The temperature difference between the opening of the thermostat and the time when the warm air is no longer delivered to the room is called ___________________. The transformer for a residential unit is used to convert line voltage to 24 volts.

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