Electric controlElectric control

Presented byPresented by

Andrew

Mitch

Sav

Little Phil

Justin

Safety requirementsSafety requirements

Correct electrical testing Correct electrical testing Correct electrical isolation procedures Correct electrical isolation procedures

as a lot of the control gear is 240 Vas a lot of the control gear is 240 V Care needs to be taken if the system Care needs to be taken if the system

is 24 v as circuits are easy to damage is 24 v as circuits are easy to damage and costly to repairand costly to repair

Avoid contact with elements with in Avoid contact with elements with in the system as they may have harmful the system as they may have harmful contents being controlledcontents being controlled

Principles Principles Uses signals sent or switch between electromechanical Uses signals sent or switch between electromechanical

devices to control valves dampers pumps just to name a few devices to control valves dampers pumps just to name a few

There are many applications where electric control can be There are many applications where electric control can be used used

Can easily be integrated in to pneumatic or electronic control Can easily be integrated in to pneumatic or electronic control

Is made up of three main components Is made up of three main components

First the disturbance sensing device First the disturbance sensing device

Second the controller Second the controller

Thirdly the final control elementThirdly the final control element

Disturbance sensing device Disturbance sensing device (sensor)(sensor)

Device that is with in the occupied space Device that is with in the occupied space which senses various elements of the which senses various elements of the space providing information to a controllerspace providing information to a controller

Is the eyes of the systemIs the eyes of the system There are many different types of DSDs There are many different types of DSDs

dependant on the application desired dependant on the application desired

Disturbance sensing devicesDisturbance sensing devices

Float switchFloat switch The float mechanism works by either by The float mechanism works by either by

making or a contact or by driving a valve making or a contact or by driving a valve arm to open or close a valve needle and arm to open or close a valve needle and seatseat

The most common form of float The most common form of float mechanism is in your toilet systernmechanism is in your toilet systern

Flexible diaphragmFlexible diaphragm Is a flexible material mounted within a housing Is a flexible material mounted within a housing that as the pressure changes the material flex’s that as the pressure changes the material flex’s driving an attached arm either backwards or driving an attached arm either backwards or forwards forwards

Pressure BellPressure Bell Sensitive to small changes in pressureSensitive to small changes in pressure

Consists of a bell shaped cap floating on oil that Consists of a bell shaped cap floating on oil that coves a stem with a hollow in the middle that coves a stem with a hollow in the middle that allows pressure to build up under the bell allows pressure to build up under the bell causing it to move causing it to move

Often used in pairs in a scale shape Often used in pairs in a scale shape arrangement arrangement

Bimetal element Bimetal element Two dissimilar metals are bonded together and Two dissimilar metals are bonded together and because of their two different coefficients of because of their two different coefficients of expansion they bend or straiten on change of expansion they bend or straiten on change of temperature most common use of bimetal strips temperature most common use of bimetal strips is in thermostats is in thermostats

Rod and tube type elementRod and tube type element A high expansion metal tube with a low A high expansion metal tube with a low expansion metal rod inside and bonded at one expansion metal rod inside and bonded at one end when the temperature around tube changes end when the temperature around tube changes the high expansion metal changes length the high expansion metal changes length Often used in insertion and immersion temp Often used in insertion and immersion temp controlscontrols

bellowsbellowsThere are three types of bellows There are three types of bellows Fluid inside fluid outside and sealed Fluid inside fluid outside and sealed

Fluid inside bellowsFluid inside bellowsThe fluid inside bellows have a linkage fixed on The fluid inside bellows have a linkage fixed on one end and the other end is connected to a one end and the other end is connected to a fluid source as the fluid source changes fluid source as the fluid source changes pressure the bellows move pressure the bellows move

Fluid outside bellowsFluid outside bellowsThe fluid outside are mounted within a housing The fluid outside are mounted within a housing which gets filled with fluid and as the pressure which gets filled with fluid and as the pressure changes in the fluid it pushes on the bellows changes in the fluid it pushes on the bellows causing them to move the linkage is connected causing them to move the linkage is connected to the inside of the bellowsto the inside of the bellows

Sealed bellowsSealed bellows

Theses are liquid or gas filled bellows much like Theses are liquid or gas filled bellows much like the liquid inside bellows except that the sensing the liquid inside bellows except that the sensing substance is sealed in and uses a remote bulb substance is sealed in and uses a remote bulb to activate the bellowsto activate the bellows

Remote bulb Remote bulb

Is a bulb connected to sealed bellows or a Is a bulb connected to sealed bellows or a diaphragm by a capillary tube which when the diaphragm by a capillary tube which when the bulb chances temp it changes the pressure of bulb chances temp it changes the pressure of the liquid or vapour within the bulb and capillary the liquid or vapour within the bulb and capillary causing drive device to movecausing drive device to move

Fast response bulbFast response bulbA fast response bulb is a capillary tube A fast response bulb is a capillary tube wound in the shape of a bulb due to the wound in the shape of a bulb due to the greater surface area of the coils the bulb I greater surface area of the coils the bulb I able to respond up to 7 times faster than a able to respond up to 7 times faster than a normal remote bulbnormal remote bulb

Averaging elementAveraging element It is a cross between a remote bulb and It is a cross between a remote bulb and fast response bulb it has the capillary the fast response bulb it has the capillary the same as a fast response only the bore is same as a fast response only the bore is larger giving it the same volume as a larger giving it the same volume as a normal remote bulb normal remote bulb

The averaging element is distributed The averaging element is distributed across the cross section of the duct evenly across the cross section of the duct evenly for a more reliable average of duct for a more reliable average of duct temperaturetemperature

Nylon ribbon / human hairNylon ribbon / human hair Nylon and human hair absorb moisture Nylon and human hair absorb moisture

from the air aroundfrom the air around Human hair or nylon is stretched between Human hair or nylon is stretched between

two points on a pivot which as the hair or two points on a pivot which as the hair or nylon absorbs moisture from the air gets nylon absorbs moisture from the air gets longer it effects the position of the pivot longer it effects the position of the pivot armarm

Wooden elementWooden element One end of a piece of timber is anchored One end of a piece of timber is anchored

so it can move and the other is free to so it can move and the other is free to move the free end is connected to a move the free end is connected to a linkage that as the timber absorbs linkage that as the timber absorbs moisture the linkage is move as the timber moisture the linkage is move as the timber expands this type of sensor is very slow expands this type of sensor is very slow acting acting

Seldom used these days Seldom used these days

Mercury switchesMercury switches Mercury switches are a glass tube filled Mercury switches are a glass tube filled

with mercury fitted to a rotary plate driven with mercury fitted to a rotary plate driven by linkages the class tube also has contact by linkages the class tube also has contact pins fitted and the tube rotates on the plate pins fitted and the tube rotates on the plate the mercury moves making or breaking the the mercury moves making or breaking the contact pinscontact pins

The controller receives information from The controller receives information from the disturbance sensing device then the disturbance sensing device then decides what to do with the information decides what to do with the information once it makes a decision it then switches once it makes a decision it then switches the final controller to do a give task the final controller to do a give task

The controller is the brains of the systemThe controller is the brains of the system

ControllerController

Forms of controlForms of controlOn off controlOn off control On off control is as the name suggests the On off control is as the name suggests the

controller simply turns the point on or off controller simply turns the point on or off as demand requiresas demand requires

Multi position on off controlMulti position on off control Is where there is more than one on or off Is where there is more than one on or off

call per mode of control I.e. one for heat 3 call per mode of control I.e. one for heat 3 for cool allowing to run more than one for cool allowing to run more than one stage of coolingstage of cooling

Floating controlFloating control Similar to on off control except that the controller Similar to on off control except that the controller

has two sets of contacts within it as temperature has two sets of contacts within it as temperature changes it can rotate to heat or cool dependant changes it can rotate to heat or cool dependant on what is required at the time this then can on what is required at the time this then can drive final control device open or closed drive final control device open or closed dependant on what is requireddependant on what is required

Proportional controlProportional control Proportional control is similar to floating control Proportional control is similar to floating control

except for instead of using a mercury switch it except for instead of using a mercury switch it uses a potentiometer to control movement of the uses a potentiometer to control movement of the valve dependent on which side the current is valve dependent on which side the current is flowing the greatestflowing the greatest

Snap acting switchesSnap acting switches Has a snap acting arm that snaps from one Has a snap acting arm that snaps from one contact to another contact when driven by a contact to another contact when driven by a plunger plunger

Mercury plunger relaysMercury plunger relaysWork similar to a solenoid valve it has a glass Work similar to a solenoid valve it has a glass tube filled with mercury a insulated contact runs tube filled with mercury a insulated contact runs up the center and one in the base of the glass up the center and one in the base of the glass tube at the top of the center contact there is a tube at the top of the center contact there is a ceramic cup also filled with mercury around this ceramic cup also filled with mercury around this contact there is a ferrous tube. this is all contact there is a ferrous tube. this is all surrounded by a electric coil that when surrounded by a electric coil that when energized drive the plunger down making energized drive the plunger down making contact between the two contacts causing a contact between the two contacts causing a circuit to form circuit to form

Electromagnetic switches Electromagnetic switches Are simple relays where one voltage is used to Are simple relays where one voltage is used to

operate a coil opening or closing contacts which operate a coil opening or closing contacts which may be carrying a greater current or load may be carrying a greater current or load

PotentiometersPotentiometers Potentiometers are fine wire wrapped around a Potentiometers are fine wire wrapped around a

core with a wiper contact that slides along the core with a wiper contact that slides along the wire wrapped around the core dependant on the wire wrapped around the core dependant on the position of the wiper the resistance changes position of the wiper the resistance changes within the core wire thus controlling the amount within the core wire thus controlling the amount of current that flows throughof current that flows through

These are used to control modulating valves These are used to control modulating valves

Final controlFinal control

Final control refers to the final Final control refers to the final element that is actually connected to element that is actually connected to the valve linkage or damper linkage the valve linkage or damper linkage to actually drive the given itemto actually drive the given item

It is the part of the system that does It is the part of the system that does the work it’s the hands of the systemthe work it’s the hands of the system

Actuators and linkagesActuators and linkages There are two main forms of final control There are two main forms of final control

devices valves and dampers valves to devices valves and dampers valves to control the flow of liquid and dampers to control the flow of liquid and dampers to control the flow of air these are driven control the flow of air these are driven by actuators connected to drive motors by actuators connected to drive motors

An actuator is the piece of equipment An actuator is the piece of equipment that starts, stops and varies the that starts, stops and varies the operation of the final control element the operation of the final control element the linkage is the flexible jointed parts that linkage is the flexible jointed parts that connect the actuator to the final control connect the actuator to the final control element element

ValvesValves Valves control the flow of liquid or Valves control the flow of liquid or

vapour by opening or closing a plunger vapour by opening or closing a plunger the plunger is connected to a stem the plunger is connected to a stem which is driven by an actuator which is driven by an actuator

Valves come in different types 2 way or Valves come in different types 2 way or 3 way valves 2 way are a open close 3 way valves 2 way are a open close type type

three way change the flow direction three way change the flow direction allowing parts of the system to be allowing parts of the system to be bypassed for example hot or cold water bypassed for example hot or cold water coils in AHUs coils in AHUs

DampersDampers Damper are blade shaped louvers Damper are blade shaped louvers

that as they rotate can control the that as they rotate can control the amount of air that flows across them amount of air that flows across them they proportion the amount of air they proportion the amount of air that flows across them by opening or that flows across them by opening or closing to particular degrees of closing to particular degrees of rotation the dampers are driven by rotation the dampers are driven by actuators and motors actuators and motors

Communication Communication between elementsbetween elements The three elements communicate The three elements communicate

with each other via electrical with each other via electrical wiring this allows the wiring this allows the communication to occur instantly communication to occur instantly and the distance between parts and the distance between parts can of great distances can of great distances

Commissioning Commissioning requirementsrequirements Check al connections are tight and secureCheck al connections are tight and secure Check all connections are correct polarity Check all connections are correct polarity Check all components correctly installed Check all components correctly installed

and in the right placeand in the right place Check correct labeling Check correct labeling Check wiring for signs of damageCheck wiring for signs of damage manually give components signals to manually give components signals to

ensure all components working to design ensure all components working to design Turn system to auto to ensure all Turn system to auto to ensure all

components work together as per designcomponents work together as per design Check for leaks on all valves and dampers Check for leaks on all valves and dampers

Service requirements Service requirements

Check al connections are tight and secureCheck al connections are tight and secure Check all installations are still correctly Check all installations are still correctly

installedinstalled Check correct labeling Check correct labeling Check wiring for signs of damageCheck wiring for signs of damage manually give components signals to ensure manually give components signals to ensure

all components working to design all components working to design Turn system to auto to ensure all components Turn system to auto to ensure all components

work together as per designwork together as per design Check for leaks on all valves and dampers Check for leaks on all valves and dampers Lubricate all moving part that require lubeLubricate all moving part that require lube

THAT’S ALL

Further information can be found in the honeywell manual from the MRB