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Primary ControlsChapter 11

Chapter 11—Primary Controls 11-3

IntroductionThe safe, automatic operation of an

oilheat system is dependent on the interac-tion between:

• The thermostat, which opens andcloses a circuit based on temperaturechanges in the heated space.

• The limit control, which opens andcloses a circuit based on temperature orpressure changes in the boiler or furnace.

• The primary control, which regulatesthe operation of the oilburner.

In a properly designed, installed, andserviced oilheat system, these threecomponents work together to safely satisfya call for space heating, cooling, or waterheating.

In a typical oilheat system, line voltageflows in a series circuit from the fuse orcircuit breaker to a remote toggle (on/off)switch located away from the heating unit.From there, it continues to a service switchat the oil-fired appliance, then to the limitcontrols, and then to the primary control,which distributes power to the oilburnercomponents (motor, igniter and oil valve).

Functionsof the primary control

The primary control has three mainfunctions:

1. To respond to the thermostat

2. To respond to the limit control

3. To control the startup, run cycle, andshutdown of the oilburner.

All primary controls, whether oldthermo-mechanical or modern micropro-cessor, operate on the same basic prin-ciples.

The primary control accomplishesits mission by:

• Reacting to the presence or absenceof flame

• Managing oilburner startup bychecking for a flame before energiz-ing ignition transformers (or ignit-ers), burner motors, and oil valves.

• Supervising burner shutdown oncethe thermostat is satisfied or the limitcontrol opens.

All primary controls have line voltage(120 VAC) circuits. In a basic heatingsystem, line voltage is supplied to theprimary control through the high limitcontrol when the temperature, in a waterheater, boiler or furnace, or the pressure, ina steam boiler, is below the limit setting.Once the limit control is satisfied, it breaks,or opens the circuit, de-energizing theprimary control and shutting down theburner.

Most primary controls also have lowvoltage circuits (24 VAC) to accommodatethermostats and/or other devices. The lowvoltage circuit is closed when the thermo-stat senses the need for an increase in room

Chapter 11Primary Controls

11-4 Primary Controls

Did you know?Power outages do not affect flame

detection. If power is lost during a runningcycle, the control will NOT go off on safetyand it will normally re-energize the burner

after power is restored.

additional control. For example, a steamboiler with a domestic hot water coil willnormally have an aquastat wired to the lowvoltage terminals on the primary control.This enables the boiler to maintain domes-tic hot water even when the room thermo-stat is not calling for heat.

Flame detectionPrimary controls detect both the pres-

ence and absence of flame. A safety featureof primary controls is that they will notactivate the oilburner for startup if thecontrol senses a flame during the off cycle.This prevents additional fuel being pumpedinto a unit that has a fire before startup.

Primary controls must react quickly tothe presence or absence of flame while theoilburner is running. The primary controlmust shut the burner off promptly if noflame is established on startup or if theflame is lost during the run cycle. If theprimary control did not shut off theoilburner in these circumstances, the burner

Figure 11-1:Parallel wiringfor 24vthermostat andaquastat to theprimary

Figure 11-3:Cad cell and itswiring symbol


Figure 11-2:Honeywell RA117aprimary control

temperature. When the heat reaches theright temperature and the thermostat issatisfied, it opens the circuit.

For the primary control to activate theoilburner, both the line and low voltagecircuits must be closed. In most cases, thatmeans that if either the thermostat or thelimit control is satisfied (open) the primarycontrol will not activate the oilburner.

In systems with a line voltage thermo-stat, or with a low voltagethermostat connected to controlsother than the primary control, ajumper is placed between theprimary’s thermostat terminals,permanently closing the lowvoltage circuit, Figure 11-1. Theprimary control is activated solelyby the limit control.

Some systems have an addi-tional control wired in parallelwith the thermostat. In thosecases, the primary’s low voltagecircuit can be completed througheither the thermostat or the

Thermostat

Aquastat

PrimaryControl

BimetalElement

Ignition Relay(RA117 only)

Mounting Bracket

Recycle Adjust Lever

Lever to Put Contacts“In Step”

Ignition Timing Adj.(RA117 only)

Motor Relay

Reset Lever onSafety Switch

Transformer


spark across the electrodes that ignites theoil is present whenever the burner isrunning.

Interrupted duty ignition means the sparkcomes on for a short timeat the beginning of eachburner operating cycle andis turned off once flame isestablished, or for a fixedtime—which may includea period of time after trialfor ignition, known as a‘Sparkout’ period—to insure a stable flameis fully established. Interrupted duty ignitionis preferred because it makes for quietercombustion, increases the life of the ignitionsystem, uses less electricity, and generatesfewer nitrogen oxide (NOx) emissions.

Types ofprimary controls

There are two basic typesof primary controls com-monly found in the fieldtoday:

• Thermal-mechanical primary controls

• Cad cell primary controls

Thermal-mechanicalcontrols, commonly called“stack switches” or “stackrelays”, utilize bi-metals todetect flame and to mechani-cally open and close electricalcontacts to provide burnercontrol. They have springloaded reset buttons and a

thermal safety switch that must cool beforethe control is allowed to be removed fromlockout.

Through the 1960’s, stack relays werethe industry’s standard primary control and

could continue to pump fuel into the unit,creating a hazardous condition.

When the primary control shuts off theburner because no flame is detected, it isreferred to as being “off on safety,” “insafety” or “in lock out.” Once the primarycontrol goes off on safety, it must bemanually reset before it can send power tothe burner again, Figure 11-4.

The amount of time that elapses fromthe start of a cycle in which flame is notdetected, to the time the control goes off onsafety is referred to as “trial for ignition”or “safety timing.” Slight variations froman individual control’s stated safety timingoften exist due to manufacturing tolerances,voltage variations, and temperaturechanges.

Ignition modesOilheat systems operate in one of two

ignition modes: intermittent duty orinterrupted duty.

Intermittent duty ignition means that the

Basic Concept of How a Safety Switch Operates

Figure 11-4: Low voltage safety switch

Did you know?Primary controls that are designed for

interrupted duty ignitioncan be adapted for intermittent duty

ignition, but primary controls designed forintermittent ignition cannot be used for

interrupted ignition.

Bimetal

Heater

WiresContacts

Insulators

Contact Blades

Spring

Spring

ResetButton

Wires



heating unit and the draft regulator. Itshould be centered in the flue pipe at apoint where it will be exposed to flue gasesbetween 300o and 1000oF. When the burneroperates, heat rises and passes over the bi-metal element, which expands and moves ashaft. This closes contacts that enable theburner to continue operating. If the bi-metal is not sufficiently heated, a built-insafety switch shuts the burner off inapproximately 75 to 120 seconds and itcannot be started again until the safetyswitch cools down and is manually reset.

Wiring• The power or “hot” lead from the limit

control is connected to Terminal 1.

• All neutrals are connected toTerminal 2.

• One wire from the burner motor andone from the oil valve, if used, areconnected to Terminal 3.

• If the unit operates as interrupted dutyignition, one wire from the trans-former is connected to Terminal 4.

• For intermittent duty ignition, connectthe transformer lead to Terminal 3along with the burner motor lead,leaving terminal 4 empty

• If the control has a green terminal, itshould be connected to ground.Figure 11-5.

Thermostat connectionsIf the control has two low voltage

terminals for the thermostat connection,one of the thermostat wires connects toeach.

If the control has three low voltageterminals and the system has a two-wirethermostat, it is connected to the W and Bterminals. If a 3-wire heat-only thermostat

Figure 11-5:Wiring diagramfor RA117A with24v 3-wirethermostat

there are many types of stack relays stilloperating in the field today. Fortunately,the manufacturers designed the wiring to bethe same regardless of the make and model.

Stack relays are typically mounted in theflue pipe, although you may occasionallyfind one mounted directly into the fluecollector or heat exchanger.

Flame detectionStack relays employ a bi-metal heat-

sensing element for flame detection. Thisheat-sensing element MUST be in the pathof the combustion gases, between the


Power Supply, Provide Disconnect Means and OverloadProtection as Required

Use Green Terminal to Connect Control Case to Ground

If Using a Two-Wire Thermostat, Tape Loose Endsof Red Wire (If Necessary)

Contacts Break in Sequence on Temperature Rise

To Replace an Intermittent Ignition Device, ConnectIgnition Leadwire to Terminal 3, Instead of Terminal 4

Series 10Thermostat

BurnerMotor High

Limit

L1(Hot)L2


is used, connect the red wire to Terminal R,white wire to W and black wire to B.

Operation of a stack relayIf all components are functioning

properly, the control is in standby modeuntil:

• Line voltage is applied through thelimit control to Terminal 1, AND a call forheat from the thermostat completes thecircuit between W and B, or T-T.

• Then Terminal 4 will be powered andTerminal 3 will be powered a split secondlater.

• The transformer will generate ignitionthrough the electrodes.

• The motor will turn the fuel pump andburner fan. If there’s a delayed oil valveinstalled, it will open based on its delaytiming.

• Once flame is established and heatedflue gases pass over and expand the bi-metal detector element, the safety switchheater will be de-energized, preventing theunit from shutting off on safety.

• The ignition circuit will be de-ener-gized, shutting off the transformer if theunit operates on interrupted ignition.

• The oilburner will then continue to rununtil either the thermostat is satisfied,opening the low voltage circuit, or the limitcontrol is satisfied, opening the linevoltage circuit. Either of these actionscauses the primary control to cut power toTerminals 3 and 4, safely shutting down theoilburner. The primary control then returnsto standby mode.

Safety checkIt is important to check the safety timing

of primary controls every time you performa service call. To check the safety timing:

• Turn off the service switch atthe unit.

• Remove the stack switch fromthe flue pipe or block the flow of oilby installing your pressure gauge inthe nozzle port.

• Turn on the service switch.

• Make sure that both the line and lowvoltage circuits are complete.

• The control should energize and shutoff on safety in approximately 75 seconds.

• If the control goes off on safety within120 seconds, clean the bi-metal andreinstall it.

• If the control does not go off onsafety, replace it and be sure to check thetiming on the new control.

Cad cell primary controlsAny system still operating with a stack

relay is probably a good candidate forreplacement with a high-efficiency oilheatsystem.

While the basicfunctions of cad cellprimary controls are thesame as those of stackrelays, they feature amuch quicker reactiontime through visual, asopposed to thermal,flame detection.

The cad cell primary control circuit ismade up of two components: the flamedetector and the primary control.

Flame detectionThe flame detector consists of a cad cell,

a holder to secure it in place, and a wiringharness to connect it to the primary control.The detector is installed in the air tube ofthe oilburner where it can view the flame.

Did you know? Cad cell primarycontrols, also called “cad cell relays,”were introduced in the early 1970’s.

Modern oilheat systems operate morecleanly, more efficiently and much more

economically than systems designedwhen stack relays were the standard.

Did you know?Cad cell resistance

looking into aninactive chambershould be at least

50,000 ohms.


Did you know? The burner manufacturerdetermines the location of the cad cell; iffor some reason an alternate location mustbe used, make sure that:

• The cell has a clear view of theflame

• Ambient light does not reach the cell

• Ambient temperature is below thecell’s rating (approx 140°F, see specs)

• Movement, shielding or radiation ofmetal surfaces near the cell does notaffect cell function.

• Avoid extreme changes in flame lightreaching the CAD cell, as pass/failthresholds in the control may notfunction properly.

The cad cell is a ceramic disc coatedwith cadmium sulfide and overlaid with aconductive grid. Electrodes attached to theceramic disc transmit an electrical signal tothe primary control. In darkness, cadmiumsulfide has a very high resistance to thepassage of electrical current. As the cell isexposed to light, its resistance decreasesand current is allowed to pass.

For a cad cell relay to start the burner,the flame detector must sense the absenceof flame and resist the passage of current.Once the burner starts and flame is estab-lished, the cell senses light, resistancedrops, current passes through the circuitand the burner continues to run.

If the cad cell does not sense enoughlight when the burner starts, the controlwill shut off on safety. It can not be started

again until thesafety switch coolsoff and is manuallyreset. Note thatelectronic safetyswitches do nothave to cool downbefore resetting. If

the flame is lost during the running cycle,very early model controls will shut thesystem down after the safety timing (15 to45 seconds) is reached; later models willmake one attempt to restart. Recycle typecontrols will shut down for 1 minute, thenallow startup, for any number of startupattempts.

WiringAs with stack mounted primary controls,

the major manufacturers adopted uniformstandards regarding wiring connections forfirst generation cad cell primary controls.

In place of the numbered screw termi-nals on stack relays, cad cell relays havecolor-coded wire leads pre-attached to thesolid-state circuitry. These wire leads fromthe control are connected to the wiring forthe system components with wire nuts.

The hot wire from the limit control isconnected to the black wire of the cad cellrelay. Some postpurge controls have linevoltage connected to a red/white wire.

The hot wire of the burner motor,igniter and oil valve are connected to theorange wire. Postpurge controls have thevalve connected to the violet wire.

The white wire is connected to theneutral lead along with the neutrals fromthe burner components.

The low voltage side of cad cell relaystypically has two terminals labeled T-T,which can be connected to the thermostat.

The cad cell flame detector leads areconnected to the F-F terminals.

Figure 11-6.

OperationThe most common first generation cad

cell primary controls you are likely tocome across in the field are the Honeywell


Cad cells can only see yellow andwhite flames. This is why they are notused on gas controls. New low NOx

oil burners burn with a transparent toblue flame and biofuels’ flames arealso more blue. Manufacturers are

using infrared or ultraviolet detectorsto see these new flames.


R8184G or the White Rogers 668. Theyboth feature intermittent duty ignition andoperate as follows:

If all components are functioningproperly, the control is in stand-by modeuntil:

• Power is applied through the limitcontrol to the black wire, AND a call forheat from the thermostat completes thecircuit between T and T. Then, assumingthat the cad cell does NOT sense light…

• The control is energized and theorange wire is powered.

• The igniter generates ignition throughthe electrodes and the motor turns the fuelunit and burner fan. If there is an oil valveinstalled, it opens based on its delay timing.

• Flame is established and the cad cellresistance decreases to fewer than 1600ohms, de-energizing the safety switchheater and preventing the unit fromshutting off on safety.

• As long as the cad cell senses flame,the oilburner continues to run until eitherthe thermostat or limit control is satisfied.

Safety checkTo check the safety:

1. Turn off the power at the serviceswitch.

2. Install a 1,000 ohm resistor acrossthe F-F terminals to reduce resistance andsimulate flame. It is OK to leave the cadcell leads hooked up.

3. Turn on the service switch and makesure that both the line and low voltagecircuits are complete.

4. The control should NOT energize,because the resistor connected to the F-Fterminals simulates a fire in the chamber. Ifit does energize, replace the control.

If it does not …

1. Turn off the service switch andremove the resistor.

2. Disconnect one lead from the F-Fterminals.

3. Turn on the electrical switch. Thecontrol should energize and the burnershould lock out based on safety switchtiming (15 – 45 seconds.) If the control


Figure 11-6:Cad cellprimary control


Power Supply, Provide Disconnect Meansand Overload Protection as Required

To Use R8184 with Line Voltage Controller, Jumper T-T Terminals andConnect Line Voltage Thermostat in Series with Limit Controller.

Line VoltageThermostat

Junction BoxR8184G Protectorelay® ControlThermostat

Cad Cell

Black

Orange

White

does not go off on safety, replace it and besure to check the timing on the new control.

4. If the control does go off on safety,reconnect the lead to the F terminal andpress the reset button. The safety is work-ing properly.

Troubleshooting tipsIf the oilburner does not start:

Verify that electrical switches are in the‘ON’ position and that the thermostat is set

above room temperature. Be sure that thereis not a fire burning in the unit.

Remove the primary control’s cover andvisually check to see if the spring-loadedmechanism has locked off on safety.

If the primary control is NOT off onsafety, check for proper voltage comingfrom the limit control.

If there is sufficient line voltage, removeone lead from the F-F terminals. If theburner starts, the problem is in the cad cell

sensor or wires. The cell may be sensinglight or the wires may have beenshorted.

If the burner does not start, discon-nect all the thermostat leads and install ajumper. If the burner starts, the problemis in the thermostat or its wiring.

Did you know? Leaving the thermostat

wiring connected to the control while

testing may harm today’s computerized

thermostats.

If the primary is off on safety, checkthe combustion chamber to be sure theunit is not saturated with oil. If thechamber contains excess oil, follow yourcompany’s procedures to eliminate theoil. Never attempt to fire an oilburnerinto a saturated chamber!

If the chamber is free of excess oil,press the reset button.

If the primary control energizes butthe burner motor does not turn—shut offthe service switch and check the electri-cal connections and the burner motorreset button.

If the burner runs and flame isestablished but the control shuts off onsafety, disconnect the cad cell leads,press the reset and, before the unit shutsoff on safety again, place a 1000-ohmresistor across the F-F terminals. If theburner continues to operate with the



Cad Cell Checkout—Burner On

IgnitionElectrode

Air Tube

C554A

OhmmeterLight CellResistanceUnder 1600ohms

Primary Control

BlowerNozzle

Remove Cad Cell Leadwires From the Primary Control

Start Burner

Jumper Terminals—Allows Burner to Run

Connect Ohmmeter to Cad Cell Leadwires—Must ReadLess Than 1600 Ohms

Cad Cell Checkout—Burner Off

IgnitionElectrode Air

Tube

IgnitionTransformer Ohmmeter

Primary Control

Blower

C554A

Start Burner

Nozzle

Remove the JumperCheck Resistance—Must Be 100,000 Ohms or MoreWhen Dark


resistor in place, the cad cell relay isoperating as designed and theproblem is with the cad cell flamedetector.

With the unit operating, connectthe cad cell leads to your ohmmeter.A reading of zero ohms indicates ashort circuit. Check for pinched orshorted cad cell wires.

If the resistance is infinite, checkfor broken cad cell wires or a looseor defective cell.

On most properly adjustedburners, the reading will be 400

ohms or less. Some burners with largestatic plates or small openings in theretention head operate in the 400-800ohm range. Very few burners operatewith resistance over 800 ohms.

If the reading is greater than 1600ohms, there is a serious problem withthe fire, the cad cell eye, its holder, itsleads or its alignment. Remember thecad cell needs to have a good viewthrough the air tube to the fire.

If the eye is coated with soot, it willnot be able to “see” the flame. Cleanthe eye and continue your trouble-shooting to find out why the eye isdirty.


Cad Cell Check List

Ohmmeter Reading Cause Action

0 ohms Short circuit Check for pinched cad cell leadwires

Less than 1660 ohms Cad cell and application Nonebut not zero are working correctly

Over 1600 ohms Dirty or defective cell, 1. Clean cell face, recheckbut not infinite improper sighting or 2. Check flame sighting

improper air adjustment 3. Replace cell, recheck4. Adjust air band to get good reading

Infinite resistance Open circuit Check for improper wiring, loosecell in holder or defective cell

Burner Locks Out On Safety

Check Primary Control

Check Cad Cell

WithOhmmeter

WithoutOhmmeter

CheckResistance

Clean Cell

Check Wiring

Check FlameAdjustment

Checking Cad Cell and PrimaryAir

TubeIgnitionElectrode

Nozzle

Blower

PrimaryControl

Ohmmeter

Remove Lead Wires From Primary ControlStart BurnerJumper F-F (With 1500 Resistor)Control Locks Out—Replace—Burner Runs—Trouble is Cad CellCheck Resistance—Infinite—Open Circuit (Cell Defective or Not Seated)Greater Than 1600 Ohms—Cell Dirtyor Not Sighting Properly

Second generationcad cell primary controls

Second generation cad cell primarycontrols have the same basic features asfirst generation controls, but steady ad-vances in technology have led to a numberof improvements.

For example, second generation cad cellprimary controls have electronic resetmechanisms which are not spring loaded.The reset button on these controls does not“pop-up” when the unit shuts off on safety,and the reset doesn’t have a thermalcomponent, so there’s no cooling timerequired before the control can be reset. Tobring the control out of safety lockout, yousimply depress the reset button for threeseconds.

Typical second generation cad cellprimary controls include:

Safety monitoring circuitThis circuit monitors the contacts of two

separate, redundant motor relays. Safetylockout occurs if the contacts of eithermotor relay are found closed when theyshould be open, thus ensuring shutdowneven if one motor relay fails.

Interrupted duty ignitionThese controls have an additional wire

that is connected to the transformer origniter. With interrupted duty ignition:

• Electrodes and igniters/transformerslast longer

• Electrical consumption, operationalnoise and NOx emissions are reduced

• Combustion problems leading to dirtyboilers and running saturations areminimized

Recycle-on-flame-failureRecycle-on-Flame-Failure means that

instead of shutting off on safety on loss offlame during the run cycle, the burner willshut off within approximately 1.5 seconds.After a wait of 60-90 seconds, the controlwill attempt to restart the oilburner.

OperationSecond generation cad cell primary

controls operate similarly to first genera-tion controls.

If all components are functioningproperly, the control is in stand-by modeuntil—

• Power is applied through thelimit control to the blackwire, AND the circuitbetween T and T is closed.

Then assuming that the cad cell doesNOT sense light—

• The control is energized and theorange and blue wires are powered.

• The ignition and motor start.

• After the cad cell senses flame, theignition stays on for another 10seconds, then shuts off.

As long as the cad cell senses flame, theoilburner continues to run until the thermo-stat or limit control is satisfied.

If the control does not sense flamewithin the control’s safety timing, lockoutoccurs. Pressing the reset button for 3seconds resets the control.

Third generation cad cellprimary controls

Third generation primary controls



include a microprocessor in the printedcircuit boards. They feature interruptedduty ignition, fifteen-second safety timingand include several new features.

“Valve-delay-on” technology—depending on the manufacturer, this featuremay be referred to as “valve-on-delay,”“delayed-valve-on,” or other similarwording. Through the use of an oil valve,“valve-delay-on” allows the burner motorto get up to speed delivering full flow fromthe fuel unit and full airflow from the fanbefore oil flows from the nozzle. Thisoptimizes fuel/air mixing at start upresulting in a significant reduction of sootbuild-up and increased efficiency.

“Motor-delay-off” technology—mayalso be referred to as “burner-motor-off-delay,” or other similar wording. Thisfeature allows the motor/fan combinationto continue delivering full air flow for aperiod of time after the oil flow through thenozzle has been cut off by an oil valve,resulting in cleaner shut downs.

Did you know? Many people in our industryrefer to “valve-delay-on” as “pre-purge”

and “motor-delay off” “post purge.” This isnot correct. The primary controls’ opera-tions do not fit the Underwriters’ Laborato-

ries (UL) definition of pre- and post-purge.

Dry alarm contacts—These auxiliaryelectrical contacts close when the controlgoes into lock out or latch up. Throughvarious added controls (i.e. an auto dialer)can alert the homeowner, alarm company,

and/or service company of the situation.

Limited reset—This feature protectsagainst the repeated pressing of the resetbutton which floods the chamber with oil.

If the control goes into lockout threetimes during a single call for heat, it goesinto a restricted mode, commonly called“latch up.” The control can be reset onlytwice, regardless of the number of times thereset button is pressed. Instructions forremoving these controls from latch-up areprinted on the underside of the controlwhere the customer cannot see them.

Limited recycle—This feature limits thenumber of times the control will attempt torestart if the flame is repeatedly establishedand then lost, preventing excessive sootingfrom repeated combustion failure.

Diagnostic LEDs—These small, low-power lights provide a significant amountof information to help the service techni-cian quickly and accurately diagnose thesituation.

ConclusionPrimary controls have evolved from

simple stack switches to microprocessorbased controls that offer greater reliability,safety and efficiency. Control manufactur-ers continue to develop new products withadvanced features that will make thecontrols in use today seem as obsolete asthermo-mechanical controls are now.

As an oilheat service technician it’simportant for you to be aware of these newcontrols so that you can continue to offerprofessional service to your customers.



Carlin• Model numbers can be found just

above the thermostat and flame detectorterminals.

• Wiring diagrams are to the left, andthe controls timings are listed above themodel number.

• For example, this xxx has an xx-second “trial for ignition” an xx-secondrecycle time, an x second “valve delay on,”an xx-second “trial for ignition,” and anxx-second “motor-delay-off.”

• There may also be a revision designa-tion printed on the lower right side of thelabel.

Carlin’s microprocessor based controls,models 50200 and 60200 feature:

Limited reset—also known as “Service-man Reset Protection.” Once these controls

go into lockout three consecu-tive times without establishingflame, the control will go intolatch-up. In order to releasethem from latch-up, depress and

hold the reset button. After10 seconds, the two diagnos-tic lights will blink alter-nately. After another 20seconds, the lights will stop

blinking. Release the button to completethe reset procedure.

Recycle-on-flame-failure—in the eventof flame loss during the run cycle, withinapproximately two seconds the 50200 will

shut the burner off and the 60200 will turnoff power to the oil valve and complete a“motor-delay-off” cycle. After a wait of60-90 seconds, the red LED light will flashfor 65 seconds, then the control willattempt to restart the oilburner.

If flame is established during the “trialfor ignition” period, the burner will resumenormal operation. If flame is not estab-lished in the “trial for ignition” period—the control will go into lockout.

Diagnostic LEDs—these primarycontrols have two diagnostic LEDs: one redand one amber.

• Amber-on signals that the control is inself-test.

• Red-on indicates that the control is inlockout

• Amber and red-on indicates that thecontrol has locked out three times during asingle call for heat and is in latch-up.

• Red flashing indicates that flame hasbeen lost during a run cycle, after trial forignition.

• Amber blinking-off every 3 to 4seconds while the control is in the standbymode indicates that the cad cell is sensinglight, or a diagnostic fault which disallowsstartup.

Wiring

Thermostat and cad cell leads connect tothe appropriate terminals.


Model 50200


Specific Microprocessor-Based Primary ControlsThe following section is intended strictly as an overview. While other

manufacturers may have similar controls, these are the units that youare most likely to encounter. Also, remember that manufacturersperiodically add improvements and additional features to their controls.

It is critical to consult product specific literature to verify informationregarding individual controls, even if they are familiar to you.

The 50200 is connected in the same wayas earlier interrupted-ignition cad cellrelays:

• The black wire connects to the limitcontrol

• The white wire connects to allneutrals

• The blue wire connects to the igniteror transformer

• The orange wire connects to theburner motor

The 60200 control has both “valve-delay-on” and “motor-delay-off” features,so the wiring is slightly more complicated:

• The black wire connects to the limitcontrol




• The violet wire connects to the oilvalve

• The red wire with white tracer (stripe)connects to constant power

OperationThe Carlin 60200 operates as follows:

Each time power is applied to the redwire with white tracer, the control performsa boot up test to verify internal operation.

After about 4 seconds, the amberLED comes on. The test continuesfor 6 more seconds and, if success-ful, the amber light turns off. Ifthe test is not successful, thecontrol repeats the test untilsuccessful.

When a call for heat is initiated,the amber LED turns on and there is a 3 to4 second delay while the control performs asafe start check. If no flame is sensed andall internal conditions are correct, the LEDturns off and the control enters “valve-delay-on” mode. The ignition is poweredand one second later, the motor is powered.

After completion of the “valve-delay-on” cycle, the control goes into “trial forignition.” The oil valve is powered andopens. Flame should be established withinthe “trial for ignition” period of 15 sec-onds. If the flame is not sensed by the endof “trial for ignition,” the control goes intolockout, the red LED comes on and the dryalarm contacts close. The control must bemanually reset by pushing the reset buttonfor one second and releasing.

Once the flame is established, theignition remains on for a short time toensure flame stability and then shuts off.

The burner will then run until the call forheat is satisfied, at which time the power tothe oil valve will shut off. The motor willcontinue to operate for the specified“motor-delay-off” period. Once that cycleis completed, the control returns to standbymode.


Model 60200


11-16 Primary Controls Chapter 11—Primary Controls 11-17

Riello primary controlsRiello primary controls are designed

exclusively for use on Riello burners.

The Riello primary control, in combina-tion with the coil of the oil valve and a cad

cell, monitors and controls allfunctions of the burner. Anauxiliary tap on the motorwindings provides a 46-volt ACpower supply to operate thecontrol. The oil valve providesthe starting and running circuitsfor the primary control througha logic board and safety

lockout switch. The ignitiontransformer is integrated into the

primary control and provides interrupted-duty ignition.

There are no thermostat terminals oncurrent Riello primary controls. An addi-tional device, such as a switching relay,must be used for low voltage thermostatconnections.

The Riello control’s safety switch isequipped with a contact allowing remotesensing of burner safety lockout. Shouldburner lockout occur, 120 Volts AC issupplied to sub-base Terminal 4 to activateany connected remote alarm systems.

Wiring• All wiring is connected through the

control’s sub-base terminals.

• A wiring diagram is supplied witheach control and serves as an insulator on

the underside of the control. This diagramshould always be left in place to protect theprinted circuit board of the control.

• When working on these controls, mostexperienced Service Technicians refer toRiello’s plastic laminated troubleshootingcard or the troubleshooting guide providedin the training manual.

OperationIf all components are functioning

properly, the control is in standby modeuntil 120 volts is supplied through the limitcontrol to Terminal 5. Then assuming thatthe cad cell does NOT sense light:

• The control is energized and Terminal6 is powered, providing 120 Volts AC tothe motor.

• The auxiliary winding tap provides 46Volts AC to power the control.

• The motor starts and establishes a 10-second “valve-delay-on.”

• The oil valve opens, supplying oil tothe nozzle line, and at the same time theignition is powered.

• Once the cad cell senses flame, theignition circuit is opened and the sparkshuts off.

• As long as the cad cell senses flame,the oilburner continues to run until thedemand for heat is satisfied.

• If the control does not sense flame





within approximately 5 seconds after“valve delay-on,” the control shuts theburner “off on safety.”

• If the cad cell loses sight of the flameat any time during the firing cycle, thecontrol immediately closes the oil valve toprevent oil flow, then goes back into“valve-delay-on” mode and makes oneattempt to relight.

Safety check• Turn off the service switch

• Remove the control box fromthe sub-base

• Remove the cad cell from thecontrol box

• Replace the control box onthe sub-base

• Turn on the service switch and makesure that the line voltage circuit iscomplete

The control should energize and theburner should “go off on safety” approxi-mately 5 seconds after the “valve-delay-on” cycle. If the control does NOT “go offon safety”, replace it and be sure to checkthe timing on the new control.

Troubleshooting tipsIn general, it is good practice to check

that the control box spades and sub-baseterminals are making good contact, and toverify that there is between 42 and 52 VoltsAC between terminals 3 and 7 while themotor is running.

If the burner stays in “valve-delay-on,”check for the following before you con-

demn the control:

• Cad cell faulty or sensing light before“trial for ignition.”

• Coil wires are reversed on Terminals1 and 2 or on Terminals 1 and 8.

• Open coil circuit, Terminals 2 and 8.To check this, connect your ohmmeterbetween terminals 2 and 8; if the coilcircuit is open, the reading will be 0 ohms.

• Open coil circuit, Terminals 1 and 2.Reading should be 1235 ohms or less.

• Note—this is for the 530 SE primarycontrol only. An open coil circuit onTerminal 1 will cause the 483 SE control tolock out.

• Insufficient voltage between Termi-nals 3 and 7. It should read 42 to 52 VoltsAC. If you have lower voltage, check theincoming supply. If there is proper incom-ing voltage, above 102 Volts AC, changethe burner motor.

If a burner with a 530 SE controlcontinues to purge and light off withimmediate flame dropout, or a burner witha 483 SE control cycles on and off in quicksuccession, check the following:

• The metal yoke for the coil may bemissing or improperly installed.

• Coil wires 2 and 8 may be reversed.

• There may be low resistance on thecoil holding circuit, terminals 1 & 2.Resistance should be 1350 ohms, plus orminus 10%. If the resistance is low, changethe coil.

The following pages show referenceguides for the Riello primary control.


1-17 Chapter 11—Primary Controls 11-17

The Honeywell R7184Honeywell’s controls differ from

Carlin’s. It is also extremely important tonote that some Honeywell models utilizedifferent wire color-coding.

Standard featuresof the Honeywell R7184 include:

Limited reset—This control canbe reset only two times before itgoes into “restricted lockout,” orlatch-up mode. The reset countreturns to zero each time a callfor heat is successfully com-pleted. To reset the control fromlatch-up, press and hold the resetbutton. The LED will go out.Continue holding the button forapproximately 30 to 45 seconds

until the light comes on again.

Limited recycle—Should the flame belost while the burner is firing, the controlshuts down the burner, enters a 60 secondrecycle delay and then attempts a restart.During the recycle delay, the LED will flashslowly—two seconds on, two seconds off.Do not confuse this with the burner being“in lockout.” If the flame is lost threeconsecutive times without successfullysatisfying a call for heat, the control goesinto lockout and must be reset manually.

Diagnostic LED—The diagnostic LEDhas four states:

• On—flame present

• Off—no flame

• 2 seconds on, 2 seconds off—recycle

• 1/2 second on, 1/2 second off—lockout and latch-up.

The LED can also be used to check cadcell resistance. When the burner is runningafter the ignition has turned off, quicklypress and release the reset button. Hold itfor only a half-second or less. The LED willflash from one to four times depending onthe cad cell resistance:

• If the light flashes once—cad cellresistance is normal: 0-400 ohms

• Two flashes means resistance isnormal: 400–800 ohms

• Three flashes is normal: 800–1600ohms

• Four flashes indicate limited resis-tance of more than 1600 ohms

• Lockout can occur above 4000 ohms.

Pump priming cycle—To facilitatepriming, the control can be placed in apurge routine by pressing and quicklyreleasing the reset button while the ignitionis on. If the control has not locked out sinceits last complete heating cycle, the lockouttiming will be extended for up to 4 minutesand the ignition will operate in the intermit-tent mode for this cycle only.

Communications port—ManyHoneywell residential combustion controls






have a communications port that allows fordata interchange between the control andother products, such as diagnostic tools,modems, zoning systems, and homeautomation.

Wiring the Honeywell R7184Currently there are four models of the

R7184: A, B, P and U. On each model, thethermostat leads and cad cell leads connectto the appropriate terminals.

R7184A• The black wire connects to the limit

control




R7184BThe B model has a 15-second “valve-on

delay” feature requiring the installation ofan oil valve. This control has an addedviolet wire that connects to that valve. Theother wire from the valve is connected tothe neutrals. All other wiring is consistentwith the A model.

R7184PThe P model has both a fixed 15-second

“valve-on delay” and a “burner motor-off-


delay” feature which may be field selectedto 30 seconds, 2 minutes, 4 minutes or 8minutes or fixed at 15 seconds. In additionto the violet wire for “valve on delay,”there is a red wire that connects to the limitcontrol, while the black wire connects toconstant power to achieve the “burnermotor-off delay” feature. All other wiringis consistent with the B model.

R7184UThe U model has all of the features of

the P models with selectable on and offdelays, plus low voltage dry alarm contactsthat are located above the thermostatterminals. On the U model you have theability to adjust dip switches that enable ordisable both the valve on delay and the“burner motor-off delay.” This makes the Umodel control the same as the A control.This way you only need to stock onecontrol on your truck. All other wiring isconsistent with the P model.

Model designations and revisionsHoneywell puts the model designations

and revision information for the R7184next to the control part number and/orprints it on the side of the control. Revi-sions are numerical and indicate whichimprovements or changes are included inthe particular control. For example, Series 1controls have different cad cell indicatorranges; Revision 2 changed the pumppriming cycle from 45 seconds to 4 minutesand added the limited recycle. Some



revisions have wires, while others havespade connectors.

Series 4 and later controls have addedsafety features. If a Series 4 control detectsflame eight seconds into “valve on delay”or 30 seconds into “burner motor-off-delay,” the control will go into lock out.This is to prevent poor starts and shut-downs due to bad oil valves. This meansthat these controls CANNOT be operatedwithout an oil valve. If the fuel unit has tobe replaced, you MUST use one with eitheran integral or external oil valve. It alsomeans that if you are replacing an earliercontrol with a Series 4 or later control, youcannot simply “cap off” the violet and/orblack wires as you could with earlierrevisions. There is also a series 5 control.See Beckett’s website for details.

Sequence of operationCurrently, the most sophisticated

Honeywell R7184 is the U model. Let’stake a look at how it operates.

Standby: When a call for heat isinitiated, there is a 2 to 6 second delaywhile the control performs a safe startcheck. If no flame is sensed and all internal



conditions are correct, the controlenters “valve on delay” mode—and theignition and motor are powered for 15seconds.

Trail for ignition: Then the controlgoes into “trial for ignition.” The oilvalve is powered and opens. Flameshould be established within the “trialfor ignition” timing of 15 or 30 sec-onds. If no flame is sensed by the endof “trial for ignition,” the control goesinto lockout and must be manuallyreset. The dry alarm contacts close andcomplete the circuit to activate anyremote alarm that is connected.

Carryover: Once the flame isestablished, the ignition remains on for10 seconds to ensure flame stability,then shuts off. The burner will then rununtil the call for heat is satisfied, atwhich time the power to the oil valvewill shut down.

Burner motor off delay: Themotor will continue to operate from 30seconds to 8 minutes depending onhow the dip switches are set. Once this“burner motor-off delay” cycle hasbeen completed, the control returns tostandby mode.

Honeywell—continued

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