Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
83 Cards in this Set
- Front
- Back
- 3rd side (hint)
|
Heating and cooling control parts |
A sensor A comparator or null detector A transmitter |
|
|
|
Sensors - sense changes in the controlled variable of the controlled medium and return those changes to the controller for evaluation. |
Three types Temperature sensors Pressure sensors Humidity sensors |
|
|
|
Bimetallic strip |
Bimetal strips - predictable bending movements of both metal pieces due to different coefficients of linear thermal. Bending movement is based on temp. |
|
|
|
Other temp sensors |
Back (Definition) |
|
|
|
Other temp sensors Helix bimetal Disk bimetal ( Defrost control) |
Back (Definition) |
|
|
|
Spring bimetal in thermostat |
Back (Definition) |
|
|
|
Rod and tube sensor |
Back (Definition) |
|
|
|
Pneumatic rod and tube sensor |
Back (Definition) |
|
|
|
Fluid-filled Bellows |
The fluid expands and contracts in response to the internal pressure change that the temp change in an attached temp sensing element causes |
|
|
|
Remote bulb sensor |
Works well in direct contact with refrigerant flow in tubes, airflow in ducts or coolers |
|
|
|
Averaging element |
Fluid filled capillary tube that measure temp across an area, such as duct opening. |
|
|
|
Fast Response element |
Has a specific use in the refrigeration industry. Decreased response time due to small amount of fluid in sensor and large proportion of temp conductive material onbthe outside of the sensor. |
|
|
|
Electronic temp sensors |
Electric sensors experience a resistance change in response to a change in its controlled variable |
|
|
|
Electronic temp sensors |
Electric sensors experience a resistance change in response to a change in its controlled variable. Extremely accurate |
|
|
|
Timers |
Time initiated time terminated Time initiated temp terminated Time initiated pressure terminated |
|
|
|
Relay timers |
Delay in make Delay on break |
|
|
|
Electromechanical time delay relays and electronic time delay relay |
Timer circuit consists of a heater in proximity to a bimetal switching element in electromechanical |
|
|
|
Defrost |
Medium temp - Offcycle defrost Low temp - Active defrosting |
|
|
|
Oil return |
Low temp system - pump down or pump out method Low temp crankcase heater |
|
|
|
Low temp system - short cycling limitation |
Delay on break timer Pump out Compressor capacity control methods CPR valves - cor type valves |
|
|
|
High discharge temp problem Only in low temp ref systems due to high compression ratio |
Insulation of suction line Compressor water jackets Fancooled compressor Discharge line temperature limit controller |
|
|
|
Temp control parameters |
Cut in temp (high) Cut out Differential Overshoot Undershoot |
|
|
|
Proportional control |
PI -Proportional mode Proportional plus integral Proportional plus integral plus derivative mode |
|
|
|
Constant cut in thermostat |
Off cycle defrost at 2.8 c |
|
|
Thermodisk thermostat |
Med and low temp Fixed factory set cut in and cut out |
|
|
|
Pump down control system |
Med temp walk in coolers Usually less than 5 ton Low pressure controller - close on rise at increasing crankcase pressure ( EPR valve) |
|
|
|
Pump out control system - low temp walk in freezer |
Addresses the problem of short cycling that is shortcoming if pump down system |
|
|
|
HVAC thermostatic controls |
Control mode - on/off and continuous ( proportional control mode) features like auto automatic reset control |
|
|
|
HVAC thermostatic controls |
Control mode - on/off and continuous ( proportional control mode) features like auto automatic reset control |
|
|
|
HVAC thermostatic controls |
Control range - maximum and minimum values between which you can set a control. Actual operating range may be smaller or narrower than the control range. |
|
|
|
HVAC thermostatic controls |
Control function - relates to the purpose and flexibility of a control. Eg night setback |
|
|
|
Thermostat |
Zone thermostat -Primary zone controller. Part of unitary control and BAS. Attach to LAN local area network, provide inputs to UC and BAS |
|
|
|
Thermostat |
Zone thermostat -Primary zone controller. Part of unitary control and BAS. Attach to LAN local area network, provide inputs to UC and BAS. Low ambient limit thermostat- prevent compressor from running if ambient temp is too cold. Usually 10 C. Protect compressor operates in cold ambient temp eg: large amount of refrigerant dissolved in crankcase oil. Changeover thermostat and enthalpy controller - Low ambient temp limit - stop compressor and cooling Free cooling economizer cycle - air cond fans bring outdoor air into building through fresh air dampers. Usually at 10-15 c. The more humid the ambient air, more effectively enthalpy controller operates |
|
|
|
Thermostat |
Zone thermostat -Primary zone controller. Part of unitary control and BAS. Attach to LAN local area network, provide inputs to UC and BAS. Low ambient limit thermostat- prevent compressor from running if ambient temp is too cold. Usually 10 C. Protect compressor operates in cold ambient temp eg: large amount of refrigerant dissolved in crankcase oil. Changeover thermostat and enthalpy controller - Low ambient temp limit - stop compressor and cooling Free cooling economizer cycle - air cond fans bring outdoor air into building through fresh air dampers. Usually at 10-15 c. The more humid the ambient air, more effectively enthalpy controller operates |
|
|
|
Changeover thermostat and enthalpy controller - Low ambient temp limit - stop compressor and cooling Free cooling economizer cycle - air cond fans bring outdoor air into building through fresh air dampers. Usually at 10-15 c. The more humid the ambient air, more effectively enthalpy controller operates |
Changeover thermostat and enthalpy controller - Low ambient temp limit - stop compressor and cooling Free cooling economizer cycle - air cond fans bring outdoor air into building through fresh air dampers. Usually at 10-15 c. The more humid the ambient air, more effectively enthalpy controller operates |
|
|
|
Mixed Air Thermostat (Mixed air controller) |
Proportional temp controllers, control the damper actuators of an economizer.. Typical set point mixed air is 10-15c Mixed air thermostat actually a mixed air controller |
|
|
|
Mixed Air Thermostat (Mixed air controller) |
Proportional temp controllers, control the damper actuators of an economizer.. Typical set point mixed air is 10-15c Mixed air thermostat actually a mixed air controller |
|
|
|
Evaporator low limit thermostat |
Prevent compressor when evaporator is too cold. Ac should never operate below 32F or 0C Prevent evaporator from freezing because it stops the compressor during these conditions |
|
|
|
High limit Thermostat |
Interrupt heating cycle in response to excessive temp that inadequate airflow causes. Set-point 80-104C Safety device Never bypass or replace with high set point thermostat. |
|
|
|
Roll out limit thermostat |
Interrupt heating cycle during primary burner rollout condition Roll out - main burner flame and glue gases remain in burner compartment, where they cause flame and heat damage, rather than being exhausted through the flue. Reasons are inadequate flue draft, cracked or fouled heat exchanger, negative building static pressure, damaged or misaligned burners. |
|
|
|
Roll out limit thermostat |
Interrupt heating cycle during primary burner rollout condition Roll out - main burner flame and flue gases remain in burner compartment, where they cause flame and heat damage, rather than being exhausted through the flue. Reasons are inadequate flue draft, cracked or fouled heat exchanger, negative building static pressure, damaged or misaligned burners. |
|
|
|
Spill limit Thermostat |
Interrupt heating control circuit if appliance has a backdraft problem Backdraft - when hot flue gases spill out of flue hood rather than drawing up the flue vent. Because of negative building pressure, plugged flue vent or incorrectly sized flue vent. |
|
|
|
Fan control thermostat |
Prevent supply air fan from starting until the heat exchanger warms to a preset minimum temperature. Improve comfort and it also prevent heat exchanger from cracking as a result from erratic and unbalanced cooling |
|
|
|
Fan control thermostat |
Prevent supply air fan from starting until the heat exchanger warms to a preset minimum temperature. Improve comfort and it also prevent heat exchanger from cracking as a result from erratic and unbalanced cooling |
|
|
|
Fan control thermostat |
Prevent supply air fan from starting until the heat exchanger warms to a preset minimum temperature. Improve comfort and it also prevent heat exchanger from cracking as a result from erratic and unbalanced cooling |
|
|
|
Electromagnetically time delay relay (TDR) and sequencer |
Provide delay on make and delay on break timer action to control circuits TDR has a heater as an actuator and bimetal switch as a transmitter. Problems: TDR is sensitive to ambient temperature changes And costly |
|
|
|
Electronic delay on make timer |
Control sequencing by time delay in stating sequence of multi stage condensing units. There is no current flow through device until the time delay on setpoint knob is complete |
|
|
|
Electronic delay on make timer |
Control sequencing by time delay in stating sequence of multi stage condensing units. There is no current flow through device until the time delay on setpoint knob is complete |
|
|
|
Electronic delay on make timer |
Control sequencing by time delay in stating sequence of multi stage condensing units. There is no current flow through device until the time delay on setpoint knob is complete |
|
|
|
Electronic delay on break timer |
Function exclusively as anti short cycle timers for HVAC applications |
|
|
|
Night set back time clock |
Force HVAC system into energy conservation mode. Modern electronic zone thermostat includes the night set back feature as an integral function |
|
|
|
High pressure limit controller |
I truly cooling control circuit during excessive ref pressure in condensing unit. Protect compressor and other system components. |
|
|
|
High pressure limit controller |
Interrupt cooling control circuit during excessive ref pressure in condensing unit. Protect compressor and other system components. |
|
|
|
Unloaded pressure controller |
Close on fall Operate unloaded solenoids which increase or decrease ref or oil pressure that applies to compressor unloaded mechanisms |
|
|
|
Unloaded pressure controller |
Close on fall Operate unloaded solenoids which increase or decrease ref or oil pressure that applies to compressor unloaded mechanisms |
|
|
|
Condenser fan controller |
Maintains a minimum discharge pressure in HVAC condensing unit by cycling the condenser fans off and on in response to discharge pressure, ambient temp or liquid line temp Prevent damage to: Compressor motor windings if there is overheat due to low refrigerant charge. Protects compressor valves and bearings during evaporator freeze ups and low load conditions |
|
|
|
OFC |
Protect compressor from failure as a result of insufficient lubrication |
|
|
|
Static pressure controller |
Senses building or duct static pressure in conjunction with various damper operations or a variable speed motor, attempts to maintain a minimum static pressure |
|
|
|
Combustion Air proving controller |
Ensure that sufficient air volume moves through gas fired appliances heat exchanger to allow safe ignition and proper combustion |
|
|
|
Actuator and positioners |
End control devises Use information from all input devices to make end control devices act to satisfy temp needs of space or process that cools or heats Actuators are electrical motors with gear box. Air mixing temperature control systems use a motorized actuator as a proportional damper positioner |
|
|
|
Actuator and positioners |
End control devises Use information from all input devices to make end control devices act to satisfy temp needs of space or process that cools or heats Actuators are electrical motors with gear box. Air mixing temperature control systems use a motorized actuator as a proportional damper positioner |
|
|
|
Economizer actuator motor |
Mix outside air with warm return air from the control zone and return mixed air back to zone Low cost air conditioning uses outside air to air condition a space |
|
|
|
Economizer actuator motor |
Mix outside air with warm return air from the control zone and return mixed air back to zone Low cost air conditioning uses outside air to air condition a space |
|
|
|
Static pressure damper positioner |
The actuator opens an exhaust damper with an increase in building static pressure Maintains volume of supply air |
|
|
|
Duct static pressure control |
As duct static pressure increases above the controller set point, the damper damper tend to close and reduce the amount of air that enters the supply fan. The reduction in volume of supply air leads to a drop in the static pressure. Conversely when duct static pressure drops too low, the dampers open and allow pressure to rise. |
|
|
|
Electronic overload All electronic overloads are rated for pilot duty operation |
Sensor for overloads sense either temperature or current and often mount externally from the overload device |
|
|
|
Ignition controller |
Sub components of most natural gas fuelled heating control systems Initiate the combustion process for the heating cycle safely |
|
|
|
Ignition controller |
Sub components of most natural gas fuelled heating control systems Initiate the combustion process for the heating cycle safely |
|
|
|
Condenser fan speed controllers Are placed in single printed circuit board (PCB) |
Maintain the head pressure of HVAC condensing unit by cycling or varying the condenser fan speed during low ambient conditions |
|
|
|
Condenser fan speed controllers Are placed in single printed circuit board (PCB) |
Maintain the head pressure of HVAC condensing unit by cycling or varying the condenser fan speed during low ambient conditions |
|
|
|
Smart Relay and Programmable Logic Controller (PLC) |
Computerized modular control systems, replace nearly all hard wiring and most of the relays and timers. They have Central processing unit (CPU) that execute program that directs the functions of the control system by semiconductor switching. Manufactures pre programs these devices and allow the installer to input some variable changes |
|
|
|
Electronic single zone Thermostat |
Have semiconductor sensors, may use internal CPU based algorithms to reduce controller deviation. Use relay contact points to interface with electrical control system HVAC are similar to ref but are diff in following ways: More complex controller and algorithm to reduce controller deviation and provide more switching options HVAC are more decorative and user friendly Low voltage 24 vac While ref thermostats are 120/240 Vac |
|
|
|
Integrated Modular Controller (IMC) |
Provide all the functions necessary to control an HVAC machine on a single PCB You can use manufacture software and an operator interphace to configure IMC May networked to a building automation system or supervisory terminal. Light emitting diode (LED) display provides the operator with error codes. |
|
|
|
Economizer Module |
Printed circuit board with an enclosure 24 vac Output analog signal to position proportional actuator Two solid state external sensors, which are outdoor air sensors and mixed air sensor Sometime have co2 sensor provide demand ventilation air to a zone and building |
|
|
|
Specific refrigeration control systems |
Back (Definition) |
|
|
|
Specific HVAC control systems |
Back (Definition) |
|
|
|
Two adjustments of economizer module |
Back (Definition) |
|
|
|
Closed loop system |
Back (Definition) |
|
|
|
Electronic control system Output signals |
Back (Definition) |
|
|
|
NEMA symbols |
Back (Definition) |
|
|
|
NEMA symbols |
Back (Definition) |
|
|
|
NEMA symbols |
Back (Definition) |
|
|
|
NEMA symbols |
Back (Definition) |
|
