The water level control has 2 float actuated mercury switches. One switch is connected to the burner limit circuit and will stop the burner if a low water condition occurs. On a steam boiler the other switch is connected to the feedwater circuit to energi
The control is of the automatic reset type and will remake the limit circuit when the water level is restored. Some applications require that a control be equipped with a manual reset mechanism that must be manually reset before the burner can be restarte
Low water cutoff devices are generally set by the original manufacturer and no attempt should be made to adjust these controls to alter the point of low water cutoff or point of pump cut-in or cut-out. If a low water device should become erratic in operat
The need to periodically check water level controls cannot be over emphasized. Most instances of major boiler damage are the result of operating with low water.
On steam boilers the head mechanism of the low water cutoff device(s) should be removed from the bowl at least once a month to check and clean the float ball, the internal moving parts, and the bowl or water column.
In addition and at the same time, remove the pipe plugs from the column, tees or crosses to make sure the cross connecting piping is clean and free of obstructions. Controls must be mounted in a plumb position for proper performance. Determine that piping
Water level controls normally function for long periods of time which may lead to laxity in testing on the assumption that normal operation will continue indefinitely.
Testing of the controls, especially on steam boilers, should be followed on a definite planned schedule. The control’s operation may be checked by stopping the water supply to the boiler while the burner is operating at low fire.
While under constant attendance allow the water to lower at a normal rate. If a control does not break the circuit to stop the burner at the proper point then SHUTDOWN THE BURNER IMMEDIATELY. Repair or replace the control at once.
A scheduled blowdown of the water controls on steam generators should be maintained.
On a hot water boiler it is impractical to perform daily and monthly maintenance of the low water cutoff devices. However, it is essential to remove the operating mechanism from the bowl annually or more frequently, if possible, to check and clean the flo
Also check any cross connecting piping to make certain that it is clean and free of obstruction. It is not practical to blowoff or drain the low water cutoff devices, since the entire water content of the system would become involved. Many hot water syste
A blowdown cock is provided on the lower gauge glass fitting and a daily blowdown is recommended. The glass should be removed every 3 months and checked, while cool, for etching, thinning, or damage. If any defects are found, replace the glass immediately
Do not over tighten water gauge glass fittings. Check try cocks and gauge cocks for freedom of operation and clean as required. Proper alignment of gauge glass cocks is essential to prevent mechanical strain on the glass.
The following instructions apply to those controls considered standard, or normally provided as optional. Space prevents listing other controls or variations of those listed that may be included in the circuitry due to job specifications or insurance carr
In general, when adjusting controls check to see that they are level, especially those containing mercury switches. On temperature sensing controls make sure that the bulb is properly bottomed in its well. Make sure that connecting tubing is not kinked or
Controls are carefully calibrated during their manufacture and do not normally require recalibration. The dial settings are generally quite accurate although it is not unusual to have a slight variation between a scale setting and an actual pressure gauge
Most of the operating controls require very little maintenance beyond occasional inspection. Examine tightness of electrical connections. Keep controls clean. If any dust accumulates in the interior of the control, remove with a low pressure air hose taki
Examine any mercury tube switches for damage or cracks: this condition, indicated by a dark scum over the normally bright surface of the mercury, may lead to erratic switching action. Make certain that controls of this nature are correctly leveled using
Dust and dirt can cause excessive wear and overheating of motor starter and relay contact and maintenance of these is a requirement.
Starter contacts are plated with silver and are not harmed by discoloration and slight pitting. Do not use files or abrasive material such as sandpaper on the contact points since this only wastes the metallic silver with which the points are covered.
Use a burnishing tool or a hard surface paper to clean and polish contacts. Replacement of the contacts is necessary only if the silver has worn thin.
The Model 5 boiler is designed to withstand considerable change in steam pressure or water temperature, however, good operating practice with any boiler is to avoid thermal shock caused by rapid and frequent variations. Therefore, it is advantageous to se
Normal operation of the burner should be with the damper positioning switch in the “auto” position. This allows the burner to automatically shift from one firing rate to another in accordance with load requirements.
The burner will be operating in low fire position prior to shutdown.
The burner will operate at low fire for a brief period on each start during normal operation.
eliminates frequent burner on-off cycling.
Figure 5-1 depicts a typical relationship of the setting of the operating limit control and the modulating control. Please note that this is not drawn to any scale. The burner will be “on” whenever the pressure or temperature is below point B and “off ” w
The distance between points A and B represents the “on-off ” differential of the operating limit control.
In normal operation, the burner will shut down whenever the pressure or temperature reaches setting A. The switch in the operating limit control will open. As the pressure or temperature drops back to B, the switch makes and the burner will restart.
The modulating control will be calling for the modulating motor to be in a low fire position at this point. If the load exceeds this low fire input, the modulating control will respond to increase the firing rate proportionately as pressure or temperatur
Point D represents the maximum firing rate of the burner. In the event pressure or temperature drops while the burner is firing at its maximum input, this is indicative that the load exceeds the generating rate of the boiler.
Although a gap is shown between B and C, these points may well coincide if required by load conditions. When set as shown, the burner will be in a low fire position upon a restart and will fire at that rate for a short period of time before falling pressu
From this illustration it can be seen that this desirable objective will not be attained if setting C overlapped point B. In that event, upon a restart, the burner would drive to a higher firing position immediately after main flame was proven, and the br
When firing a cold boiler, it is recommended that the burner be kept under manual flame control until normal operating pressure or temperature is approached. The size of the flame may be manually and gradually increased to build up pressure or temperature
This rapid heat input can subject the pressure vessel metal and refractory to undesirable conditions. A 10 minute low fire hold is incorporated to slow this rapid heat input.
Any control setting must not cause the boiler to operate at or in excess of the safety valve setting. Settings that do not exceed 90 percent of the valve setting are recommended, with lower settings greatly desirable if load conditions permit. Avoid havin
Continued leakage, however slight, will cause erosion and necessitate early valve replacement. The control settings on a hot water boiler must be within the temperature and pressure limits of the boiler.
Ideally, the burner operating controls should be set under actual load conditions. Often, especially on new construction, the boiler is initially started and set to operate under less than full load requirements. As soon as possible thereafter the control
To accomplish this, and assuming that air/fuel combustion ratios have been set, make approximate adjustments to the controls to bring the boiler pressure or temperature up to meet the load requirements.
To properly set the modulating control, carefully adjust it under load conditions, until the load is maintained with the burner firing at a steady rate. The firing rate at that point may be full high fire or slightly less, depending upon the relationship
When the modulating control is set in this manner and if the burner is in full high fire, the scale setting of the modulating pressure control on a steam boiler will have a reading that indicates the low point of the modulating range. T
This fixed differential range is described later in this section. The scale setting of the modulating temperature control on a hot water boiler will have a reading that indicates the midpoint of the modulating range. This is also described later.
The operating limit control should now be adjusted and its differential established. See directions later in this section for the mechanics of adjusting. In an installation that does not require a very close control of steam pressure or water temperature,
The high limit control provides a safety factor to shut the burner off in the event the operating limit control should fail to do so. The setting of this control should be sufficiently above the operating limit control to avoid nuisance shutdowns
The setting, however, must be within the limits of the safety valve settings and preferably not exceed 90 percent of the valve setting. The control requires manual resetting after tripping.
In the setting of these controls, consideration must be given to the time required for a burner restart. Upon each start, there is a pre-purge period of some length, plus the fixed time required for the proving of the pilot and main flame.
This, plus approximately one-half minute required for damper motor travel from low to high fire, may allow pressure or temperature to drop below desirable limits.
The pressure controls that serve as the operating limit control and as the high-low fire control are equipped with an adjustable differential setting. See the following portion of this section for adjustment procedures.
Basically, the switch in the control opens when the steam pressure reaches a pressure equal to the main scale setting and closes at a pressure equal to that shown on the main scale, minus the amount of differential.
In an installation that does not require very close control of the steam pressure, the differential setting should be adjusted to its maximum, since this will provide less frequent burner cycling.
The control settings should not cause a boiler to operate at or in excess of the safety valve setting. Control settings that do not exceed 90 percent of the safety valve pressure are recommended. Operation of the boiler very close to maximum valve setting
Continued leakage through the valve will cause erosion to its components and necessitate early replacement. Therefore, the steam pressure control should be adjusted to operate the boiler at the lowest pressure required to satisfy the load demand.
The high-low fire control should be set to open at 5 to 10 psi lower than the operating limit setting. The suggested setting on a low pressure steam boiler is 2 to 3 psi. The differential setting on this control may be set low, to give quite close control
In any case, the control should be adjusted so that it de-energizes the damper motor, causing the burner to go to low fire, at a pressure below the limit control opening point. When the pressure controls are properly set the burner will maintain steam dr
On a rise in steam pressure, the high-low fire control opens its contacts and the damper motor returns to low fire position. The burner continues to operate at low fire rate. If steam pressure drops, the control will again close to energize the damper mot
Should the boiler pressure reach the set point of the operating limit control, its contacts will open to turn off the burner.
When boiler pressure drops, the operating limit control contacts close, causing the burner to restart. It is desirable to have the high-low fire control adjusted so that the burner does not immediately go to high fire upon start, but rather operates at lo
The temperature controls that serve as the operating limit control and as the high-low fire control are equipped with an adjustable differential setting.
Basically the switch in the control opens when the water temperature reaches a temperature equal to the dial setting and closes at a temperature equal to the dial setting minus the amount of differential. See the following portion of this section for inst
In an installation that does not require very close control of the water temperature, the differential setting should be adjusted as widely as possible since this will provide less frequent burner cycling.
The operating limit temperature control should be set slightly above the highest desired water temperature and within the limits of the pressure vessel.
The high limit control should be set 5 to 10 degrees above the operating limit temperature control setting. The high-low fire control should be adjusted so that it is below the burner “on” temperature of the operating control.
High-Low Fire Control (high fire) With settings similar to these, the following operational sequence occurs. On a rise in boiler water temperature, the highlow fire control opens its contacts at 170º F to de-energize the damper motor and place the burner in its low fire range.
If temperature decreases during low fire, the burner will return to high fire as soon as the high-low fire control closes at its 165º setting. As temperature increases during high fire rate, the burner will be switched back to low fire when the control op
The settings listed are typical and will vary according to job requirements. However, setting the controls with these relations to each other is desirable, since they will prevent the burner from shutting down while in high fire or from immediately going
Set “cut out” (burner off) pressure on the main scale using the large adjusting screw. Set differential on the short scale turning the small adjusting screw until the indicator points to the desired difference between cut out and cut in pressures.
The “cut in” (burner on) pressure is the cut out pressure minus the differential. The cut out pressure should not exceed 90 percent of the safety valve setting
Set “cut out” (burner off) pressure on scale using adjusting screw. The control will break a circuit to shut off the burner when pressure reaches this point. The setting should be sufficiently above the operating limit pressure control to avoid nuisance s
This control requires manual resetting after tripping on a pressure increase. To reset, allow boiler pressure to return to normal and then press the reset button.
Set the “cut out” pressure, the point at which the burner will return to low fire, on the main scale using the large adjusting screw
This setting should be sufficiently below the cut out setting of the operating limit control so that the burner will return to the low fire position prior to shutting off at the operating limit.
The “cut in” pressure, the point at which the burner drives to high fire, is set on the differential scale. This setting is equal to the cut out pressure minus the amount of the differential.
It should be adjusted so that it is sufficiently below the burner “on” pressure of the operating control so that the burner, when starting, will operate briefly at the low fire position prior to advancing to high fire.
In 0 - 15 psi controls the range is 1/2 lb.
In 5 - 150 psi controls the range is 5 lbs.
In 10 - 300 psi controls the range is 12 lbs.
Set “cut out” (burner off) temperature on scale by inserting a screwdriver through the cover opening to engage the slotted head adjusting screw.
The “cut in” (burner on) temperature is the cut out temperature minus the differential. The differential is adjustable from 5º to 30º F. Differential is adjusted by rotating the wheel on the back of the snap switch.
Set the “cut out” (burner off) temperature on scale using adjusting screw. This control will break the circuit and lockout on a rise in water temperature above the setting.
The setting should be sufficiently above the operating limit temperature to avoid unnecessary shutdowns. The control requires manual resetting after tripping on a temperature increase.
To reset, allow water temperature to drop below the cut out setting, less differential, and then press the manual reset button.
Set timer at a minimum of 10 minutes to a maximum of 30 minutes. This control prevents the boiler modulating or going to high fire before the timer runs out to help minimize thermal shock.
Set normally for 35 psi by setting the “cut out” (burner off) pressure on scale using adjusting screw. The control will break a circuit to shut off burner when pressure falls to this point.
Set the “cut out” temperature, the point at which the burner will return to low fire, on the indicating dial
This setting should be sufficiently below the cut out setting of the operating limit temperature control so that the burner will return to the low fire position prior to shutting off at the operating limit.
The “cut in” temperature, the point at which the burner drives to high fire, is set on the differential scale. This setting is equal to the cut out temperature minus the amount of the differential.
l. It should be adjusted so that it is sufficiently below the burner “on” temperature of the operating control so that the burner, when starting, can operate briefly in the low fire position prior to advancing to high fire.
Turn knob on front of case until pointer indicates desired set point temperature. This is the center point of a proportional range. The control has a 3º to 30º differential and may be adjusted to vary the temperature range within which modulating action i
The operating limit control may be checked by observing the burner shut-off and restarting points. With a light load it may be necessary to manually set the burner at the high fire rate to obtain burner shutdown.
With a heavy steam load the header valve can be throttled to allow pressure buildup. Make any necessary adjustments to obtain cut out at the desired point.
Note the setting at which burner restarts and adjust differential setting if necessary.
Allow pressure or temperature to build up and set the “high-low” fire control to obtain turndown at the desired setting.
Check the point at which the burner returns to high fire and adjust control differential if required.
Observe the ignition and programming control operation to be sure that these are proper.
Refer to Section 5.10 of this chapter for information on flame safety check and place the burner through these tests.
The low water cutoff, and pump operating control, if used, should also be checked for proper operation. Refer to Section 5.3 of this chapter for information relative to testing this control.
Air pressure against the diaphragm actuates the switch which, when made, completes a circuit to prove the presence of combustion air.
Since the pressure of the combustion air is at its minimum value when the damper is full open, the switch should be adjusted under that situation.
It should be set to actuate under a condition of minimum pressure, but not too close to that point to cause nuisance shutdowns.
This control requires no adjustment, nor should any attempt be made to alter contact settings. The contacts may require occasional cleaning. If so, follow instructions given in the manufacturer’s bulletin.
Do not use abrasive materials. The control cabinet door should be closed during normal operation.
The manufacturer's bulletin also contains troubleshooting information.
Replacement of internal components, other than the plug-in amplifier, is not practical or recommended. A spare control is suggested and this should be rotated periodically so that each unit will be placed into operation at least every 90 days
A periodic safety check procedure should be established to test the complete safeguard system at least once a month or more often. This test should verify safety shutdown on loss of flame and also fuel valve tightness.
The flame detector lens should be cleaned as often as operating conditions demand. Use a soft cloth, moistened with detergent if necessary. The UV sensing tube within the flame detector is not field replaceable
If the flame detector is replaced, be sure to properly connect the blue lead to the F terminal and the white lead to the G terminal. Reversing the leads even momentarily may destroy the UV tube.
Turn adjusting screw until indicator on scale moves to a pressure setting slightly below the operating gas pressure. The control will break a circuit if pressure is below this value
The control should be finely adjusted to prevent operation with low gas pressure, but should not be set at a value close enough to normal operating pressure to cause unnecessary shutdowns.
When setting this control, consideration must be given to the fact that gas line distribution pressure may decrease under some conditions and it is advisable that the control does not cut out unnecessarily.
The switch must be manually reset after tripping on a drop of gas pressure below the cut out setting. To reset, allow gas pressure to rise and press the manual reset button.
Turn adjusting screw until indicator on scale moves to a pressure setting slightly above the maximum operating gas pressure
The control will break a circuit if pressure exceeds this value. The control should be adjusted to prevent operation with excessive gas pressure but should not be set at a value close enough to normal operating pressure to cause unnecessary shutdowns.
This switch must be manually reset after tripping on rise of gas pressure above the cut out setting. To reset, allow gas pressure to drop and press the manual reset button.
This control prevents burner from igniting or stops its operation when the oil pressure drops below a set point.
The control contains a single-pole, single-throw mercury switch which closes on a pressure rise.
Pressure settings are made with the knobs on the face of the control. The “low” setting indicates the point at which switch action takes lace on a pressure drop.
Initially set this knob to the bottom of the scale. Adjust the “high” knob to a point slightly below the normal operating oil pressure. Then set “low” knob somewhat lower but not less than 150 psi. The burner will operate as long as oil pressure exceeds t
Relatively few adjustments can be made to the burner drawer, however, a check should be made to see that all components are properly located and that all holding devices such as setscrews are properly tightened.
The burner drawer should be periodically inspected for evidence of damage due to improperly adjusted combustion.
The air cooling tubes surrounding the nozzles should be inspected occasionally for any carbon residue or any clogging that might be caused by an unusually dusty or lint-laden atmosphere.
The setting of the oil nozzle in relation to the opening in the cooling tube is important and should be maintained.
Proper positioning of the diffuser should be maintained so that oil spray or flame does not impinge on it.
Remove any carbon or other deposits if any have accumulated so that air flow pattern is not affected.
Do not attempt to change the gap or angle of the fins.
Efficient oil burner operation requires clean nozzles. The nozzles furnished on the Model 5 burner deliver a spray of extreme fineness to assure proper mixing with the air stream
If at any time the flame becomes “stringy” or “lazy” it is possible that one or more of the nozzles is clogged or worn. Even though the oil pressure gauge may indicate correct pressure, plugged or partially plugged nozzles will greatly reduce oil deliver
The nozzles may be cleaned, however, if they appear worn or if they have been in service for a considerable time, it is more economical to replace them.
Any cleaning should be done with a wood splinter rather than with any metal to avoid damaging the hole in the tip or the oil grooves. Check strainer and clean if necessary.
Nozzles may be of different capacities and it is extremely important that they are replaced in proper firing order. Nozzles can be identified by the capacity and spray angle stamped on them. See Figure 5-4 for proper location of nozzles.
The capacity stamped on the side of the nozzle represents delivery rate with oil pressure at 100 psi. Since the burner is designed to use considerably higher atomizing oil pressures, the capacity of the nozzle is greatly increased.
Do not assume that undersized nozzles are installed on the basis of nozzle marking compared to the burner input.
The oil pressure required for full burner input is approximately 200 psi. Oil pressure is adjusted by the regulator in the fuel oil pump and final pressure setting may be slightly higher or lower
If smoke occurs at open damper, the pressure should be adjusted downward to clear the fire. See the later section covering oil burner combustion adjustment.
Maintain the proper gas dimensions of the ignition electrode(s) for best ignition results. Figures 5-2 or 5-3 show the correct settings.
Inspect electrode tips for signs of pitting or combustion deposits and dress as required with a fine file.
Inspect the insulators of the electrodes and the feed through insulators for evidences of cracks or chipping. If any are present, replace the items, since this can cause grounding of ignition voltage.
Carbon is an electrical conductor, so it is necessary to keep the insulating portion of the electrode wiped clean if any carbon is present. Ammonia will aid in removing carbon or soot.
Check ignition cables for cracks in the insulation. Also see that all connections between transformer and electrodes are tight.
The V-belt driving the oil pump requires no servicing and no preservatives or dressing compounds should be used. Belts normally stretch with use and proper tension should be maintained.
Do not apply excessive tension since this can result in damage to the pump shaft bearings.
On combination fired units it is an acceptable practice to remove the belt when gas is being used for extended periods, although it is not absolutely necessary to do this.
If left connected, oil will merely be circulated back to the tank. However, the pump and belt life will be extended if the belt is removed.
The oil pump has a built-in strainer of the self-cleaning knife that normally requires no servicing, however, any other strainers or filters in the suction line must be cleaned periodically.
Problems attributed to the pump can generally be traced to other causes such as broken or restricted fuel lines, lack of fuel, clogged filters, stuck or closed valves, a high vacuum, or even an excessive head of oil.
The pressure gauge reveals that the pump gears are pumping and building up a steady, even pressure to deliver oil to the nozzles and at the pressure to which the integral regulator has been set.
Collapse of the nozzle spray below the set limit can indicate worn internal parts, although these units are designed to give long periods of operation without undue wear.
If this situation is verified, it is generally advisable to replace the pump. It is recommended that removed pumps be returned to the factory for complete reconditioning rather than replacement of individual parts.
If the oil supply is below the level of the pump, a vacuum gauge installed at the suction port of the pump is helpful in checking the condition of the suction line and aids in pinpointing problems.
Normally, a vacuum reading should not exceed 10”. Vacuums higher than this can lead to problems in oil separation or in erratic or declining delivery
Excessive readings can indicate restrictions such as kinked or clogged lines, sticking or closed valves, or even a frozen oil line.
If there is no reading, look for air leaks in the lines, valve fittings, or pump. On gravity fed installations a vacuum gauge should read zero. If not, this is evidence of restrictions being present.
If the oil supply is above the level of the pump, a pressure gauge installed in the pump bypass port may be used to determine that the head of oil is not too great.
If the head pressure is over 10 psi, damage or seal leakage can occur. A pressure reducing valve should be installed in this instance. Seal leakage may also be caused by restrictions in the return line.
As an initial startup a pump noise in the form of a whine may be noticed. This is a condition that results from air in the oil line and should cease as soon as the pump is able to clear the line of air.
If the condition persists after a long period of operation, it may indicate a leak in the suction line.
Each boiler is adjusted prior to shipment from the factory, however, circumstances caused by shipment, installation, or operating load conditions may require further adjust met to assure maximum operating efficiency and economy
Periodic rechecks of adjustments and settings are also recommended.
The burner system should be adjusted on the basis of a combustion efficiency analysis after the unit has been in operation sufficiently long to assure a warm boiler.
Proper air-fuel ratio should be established by the use of a combustion gas analyzer.
This instrument measures the content by percent of carbon dioxide (CO2), oxygen (O2), and carbon monoxide (CO) in the flue gas. Efficiency is measured by the percentage of CO2 present in the flue gas.
The ideal setting from a standpoint of efficiency is reached when there is no measurable percentage of oxygen present. It is, however, more practical to set the burner to operate with a reasonable amount of excess air to compensate for minor variations in
Excess air of 15 to 20 percent is considered normal. A CO2 range of 12 to 13 percent is desirable. The burner should never be operated with an air-fuel ratio that indicates a detectable percentage of carbon monoxide.
Turn the burner to high fire and let it operate at this rate for several minutes.
Observe the color and size of the flame. Color alone is a poor means of determining efficiency, although it can serve as a guide for tentative setting
. If smoke or haze is visible, additional combustion air is required. If the flame is overly bright, rumbles or emits sparks, the amount of combustion air will have to be reduced.
Determine that the proper atomizing oil pressure exists as mentioned in the preceding section covering nozzles.
In some instances, conditions may require that the oil pressure be reduced below the suggested setting if a desired flue gas analysis cannot be obtained with an open damper.
Take a sample of flue gas with an instrument known to be in good working order and determine CO2 reading. Based on this analysis, make any required adjustments to increase or decrease air flow. See the section on air damper adjustment in this chapter.
Recheck low fire to determine whether it was affected by high fire adjustments. If so, additional linkage adjustment may be required.
Relatively few adjustments can be made to the burner drawer, however, a check should be made to see that all components are properly located and that all holding devices such as setscrews are properly tightened.
Periodically inspect the burner drawer for evidence of damage due to improperly adjusted combustion.
Check the gas pilot electrode for proper setting and also for any cracks in the porcelain insulator. Cracks can cause grounding of ignition voltage
Check the electrode tip for signs of pitting and dress as required.
Check the ignition cable for insulation cracks. See that all connections between transformer and electrode are tight
The size of the gas pilot flames is regulated by adjusting the gas flow through the pilot gas regulator.
The flame must be sufficient to ignite the main flame and to be seen by the flame detector, but an extremely large flame is not required
An overly rich flame can cause sooting of the flame detector. Too small a flame can cause ignition problems.
To check the pilot flame, visually observe it through the rear sight port.
A flame that encircles approximately one half of the diffuser is satisfactory.
To control the flame size, make the necessary adjustment to the gas pilot regulator.
A preferred method of setting a flame is to obtain a micro-amp reading of the flame signal.
This can be measured with a good quality micro-ammeter or a suitable multi-meter with a 0 to 25 micro-amp DC rating.
The meter is connected to a jack in the amplifier of the flame safeguard control. Use a meter connecting plug harness (Cleaver-Brooks part number 884-72).
Connect the plus (red meter lead) to the red tab of the harness, and the minus (black meter lead) to the black tab before inserting the plug in the meter jack.
Turn the damper switch to low.
Fully open the pilot shutoff cock.
Close the cock in the main gas line.
Connect the micro-ammeter as outlined above.
Turn the burner switch on. Let the burner go through the normal pre-purge cycle. Relay 2K should pull in when the pilot ignites with the programmer in test.
If the pilot flame is not established within 10 seconds, turn off the burner switch. Repeat the lighting attempt.
When the pilot flame is established, remove the flame detector from the burner plate. The pilot flame can then be observed through this opening.
To make the final adjustment, slowly close the gas pilot regulator until the flame can no longer be seen through the sight tube. Then slowly open the regulator until a flame providing full sight tube coverage is observed.
This adjustment must be accomplished within the time limit of the safety switch or approximately 30 seconds after the detector is removed.
Observe the reading on the micro-ammeter. The reading should be between 2 and 5 micro-amps and the reading must be steady. If the reading fluctuates, recheck the adjustment. Make sure that the flame detector is properly seated and that the lens is clean.
Reset the programmer from the “test” position to the “norm” position.
. If main flame has not been previously established, proceed to do so in accordance with instructions in Chapter 4.
The micro-amp reading of the main flame signal should also be rechecked. Observe the flame signal for pilot alone, pilot and main burner flame together, and the main burner flame at high, low, and intermediate firing rate positions.
Readings should be steady and in the range of 2 to 5 micro-amps. If there are any deviations, refer to the troubleshooting section in the technical bulletin.
The gas burner housing surrounding the diffuser plate should be periodically checked for any signs of damage that might be caused by an improperly adjusted burner or be a poor seal to the refractory.
Routine maintenance should include this resealing which can be done with a mixture of refractory cement and cement pulp. Use care not to clog or obstruct the holes in the face of the gas housing.
The diffuser should be positioned as shown in Figure 5-3. do not attempt to change the gap or angle of the fins.
To achieve rated capacity of the boiler, a sufficient volume of gas must be supplied to the burner. It must also be at a pressure high enough to overcome the pressure loss due to the frictional resistance imposed by the burner system and control valves.
A pressure regulator is provided for reducing the incoming pressure to a level that produces a steady, dependable flame, yet prevents over-firing.
The pressure requirement varies with burner size, altitude, and type of gas train.
The volume, or rate, of gas input is readily measured in terms of cubic feet per hour and can be determined from a meter reading. The flow rate required for maximum boiler output is dependent upon the heating value of the gas (BTU/cu. ft.).
To determine this flow rate, divide the boiler input requirement by the heating value (BTU/hr. ÷ BTU/cu. ft.). The BTU rating is shown on the boiler nameplate. The heating value of the gas is available from the gas supplier.
After operating for a sufficient period of time to assure a warm boiler, adjustments should be made to obtain efficient combustion.
The appearance or color of the gas flame is not an indication of its efficiency since an efficient gas flame will vary from transparent blue to translucent yellow.
Proper setting of the air-fuel ratios at all rates of firing must be established by the use of a combustion gas analyzer.
This instrument measures the content, by percentage, of carbon dioxide (CO2), oxygen (O2), and carbon monoxide (CO) in the flue gas.
Burner efficiency is measured by the amount or percentage of CO2 present in the flue gas.
The theoretical maximum CO2 percentage for natural gas is approximately 11.7 percent.
As shown in Figure 5-5, this is attained when there is no excess O2 or CO.
A definite percentage of excess air (O2) is required by most local gas authorities and of course, the burner should never be operated with an air-fuel ratio that indicates a detectable percentage of CO2.
Subject to local regulations pertaining to specific amounts of excess oxygen, it is generally recommended that CO2 readings of between 9.5 and 10.5 percent be attained with corresponding O2 readings of 2 to 4 percent.
Basically, gas adjustments are made with a gas pressure regulator which controls the pressure and with the butterfly gas valve which directly controls the rate of flow.
Back off the low fire stop screw on the butterfly valve so that the valve is closed.
Run the screw out to touch the arm and give it two complete turns.
Adjust the connecting rod so that override tension is released and so that the arm is now just touching the stop screw
Tighten the lock nuts on all ball joints.
Turn the manual flame control switch to open
At high fire position the butterfly valve should be wide open as indicated by the slot on the end of its shaft. Set and lock the high fire stop screw until it is just touching the valve arm.
Determine the actual gas flow from a meter reading.
With the butterfly valve open and with regulated gas pressure set at the calculated pressure, the actual flow rate should be quite close to the required input.
If corrections are necessary, increase or decrease the gas pressure by adjusting the gas pressure regulator, following manufacturer’s directions for regulator adjustment.
When proper gas flow is obtained, take a flue gas analysis reading. The CO2 should be between 9.5 and 10.5 percent and the corresponding O2 reading should be 2 to 4 percent.
With the high fire air-fuel ratio established the gas pressure regulator needs no further adjustment.
After making certain that the air control damper and its linkage are correctly adjusted to provide the proper amount of secondary air and after adjusting the gas pressure regulator, final adjustment can be made, if necessary, to the gas modulating cam to
Since the input of combustion air is ordinarily fixed at any given point in the modulating cycle, the flue gas reading is determined by varying the input of gas fuel at that setting
This adjustment is made to the metering cam by means of adjusting screws (Figure 5-7) which are turned out (counterclockwise from the hex-socket end) to increase the flow of fuel, and in (clockwise from the hex-socket end) to decrease it.
Through the manual flame control switch, position the cam so that the adjusting screw adjacent to the end or high fire screw contacts the cam follower.
Make a combustion analysis at this point.
Adjust the cam screw as necessary
Repeat this process, stopping at each adjusting screw until low fire position is reached.
If all screws are properly adjusted, none will deviate from the general overall contour of the cam face. It may be necessary to readjust the setting of the low fire stop screw in order to obtain the proper air-fuel ratio at low fire burning rate.
To ensure that the low fire position of the butterfly valve is always the same, allow one turn of the stop screw for over-travel.
Your gas supplier can generally furnish a chart developed to determine the cubic feet/hour reading from the meter based on the number of seconds per revolution of the 10 cubic feet dial. This provides a knowledge of the flow rate after a relatively short
Turn off all other gas appliances that may be served by the meter.
Set burner at high fire.
Note meter reading and record consumption for 3 minutes.
Input (BTU/hr) divided by Heating Value (BTU/cu. ft.) divided by 20 = gas input in cubic feet for 3 minutes
If the input timed for 3 minutes does not agree with the rating indicated by the formula, adjust the gas pressure regulator to increase or decrease flow as required.
Frequently other gas fired equipment which cannot be turned off is served by the same meter and it will not be possible to get an actual meter reading. In this event an alternate method of setting high fire fuel-air ratio using a flue gas analyzer may be
This is done by adjusting gas flow when the air damper is approximately 90 percent open
Adjust fuel flow through the regulator and butterfly to match the available combustion air and make adjustments until the combustion efficiency described in the next section is achieved.
The flow rate outline in the previous section is figured on a “base” pressure which is usually atmospheric or 14.7 psi.
Meters generally measure gas in cubic feet at “line” or supply pressure.
The pressure at which each cubic foot is measured and the correction factor for this pressure must be known in order to convert the quantity indicated by the meter into the quantity which would be measured at “base” pressure.
To express the volume obtained from an actual meter reading into cubic feet at base pressure it is necessary to multiply the meter index reading by the proper pressure factor obtained from the table in the previous section, 5.7.5 — Checking Gas Flow.
Conversely, to determine what the meter index reading should be in order to provide the volume of gas required for input, divide the desired flow rate by the proper pressure correction factor.
This answer indicates the number of cubic feet at line pressure which must pass through the meter to deliver the equivalent number of cubic feet at base pressure.
Each boiler is adjusted for proper operation prior to shipment from the factory, however, circumstances due to shipment, installation, different fuel characteristics, or operating load conditions may require further adjustment to assure maximum operating
Adjustments to obtain efficient combustion should be made after the boiler has operated for a sufficient period of time to assure a warm boiler.
The appearance or color of the gas flame is not an indication of its efficiency since an efficient gas flame will vary from transparent blue to translucent yellow
Proper air-fuel ratio should be established by the use of a combustion gas analyzer. This instrument measures the content, by percentage, of carbon dioxide (CO2), oxygen (O2), and carbon monoxide (CO) in the flue gas.
Burner efficiency is measured by the amount or percentage of CO2 present in the flue gas. The theoretical maximum CO2 percentage for natural gas is approximately 11.7 percent.
This is attained when there is no excess O2 or CO. A definite percentage of excess air (oxygen) is required by most local gas authorities and, of course, the burner should never be operated with an air-fuel ratio that indicates a detectable percentage of
Subject to local regulations pertaining to specific amounts of excess oxygen, it is generally recommended that CO2 readings of between 9.5 and 10.5 percent be attained with corresponding O2 readings of 2 to 4 percent.
The damper motor should be able to complete its full travel range of 90 degrees. A restriction can cause damage
Initial adjustment is done with the motor in its closed or unpowered condition. The power end of the shaft will be in its most counterclockwise position.
Secure the motor arm approximately 60 degrees below the horizontal center line.
The slot end of the damper shaft indicates the position of the damper blade
It is not practical to list specific setting of all connections or of the damper arm angle, since adjustment conditions must exist to meet combustion requirements or load conditions.
The closer the swivel joint in the motor arm is to the hub, the less distance it will travel.
The amount of damper opening increases when its connecting joint is closer to the hub. To decrease opening, move the ball joint away from the hub.
Final adjustments should result in a coordinated movement of the damper and damper motor.
Turn the damper positioning switch to “high” or “open” and observe the burner as it progresses to high fire, to be sure that air flow is coordinated with fuel flow.
Too much air can extinguish the flame and damper travel must be regulated accordingly. When high fire position is reached, again observe the flame appearance. If it is hazy then more air is required.
Determine approximate setting by following the procedure outlined in the preceding paragraph to obtain a haze-free fire. Again, make a reference mark showing the open position..
With the limits of low fire and high fire damper travel determined from reference marks, adjustment can now be made to the connecting rod connections, using the foregoing suggestions.
Periodically check for proper adjustment. Check tightness of setscrews to prevent slippage. Occasionally oil swivel joints with a graphite or silicone type lubricant
Rotation of the fan is counterclockwise when viewed from front of the burner. If the motor is ever replaced, be sure that rotation is proper when motor leads are reconnected.
Occasionally check to see that the fan is securely tightened on the motor shaft. A retaining washer on the end of the motor shaft holds the fan in the proper position and there should be no rubbing or contact with the air inlet.
If the boiler is installed in a dusty location, check the vanes for deposits of dust or dirt, build up of such deposits can cause a decrease in air capacity or lead to an unbalanced fan condition.
The variables involved preclude specifying the position of the cam(s) by degree of angle.
This especially applies to the cams for the oil valve switches and the high fire switch, since their point of actuation is directly related to the amount of damper travel on a particular burner.
Damper movement may be set to a greater or lesser amount of opening depending upon job conditions and combustion needs. Cam position can best be explained by detailing the function of the switch it actuates.
From one to four switches are used depending upon the type of fuel and insurance requirements.
The low fire switch (LFS), used on all boilers, must be closed to complete programmer circuitry, thus assuring that the damper is in low fire position before ignition takes place.
The switch opens when the damper motor drives to high fire during pre-purge and closes when the motor resumes its low fire position upon completion of pre-purge.
The cam, therefore, must be positioned so that it actuates this switch just prior to the damper reaching its closed position.
The high fire switch (HFS) is used, when required, to prove that the air damper is opened during pre-purge.
Its terminals should make when the damper is nearly open and just before the timing of the programmer de-energizes the damper motor. See wiring diagram for sequence timing of the control.
An oil fired boiler uses two switches to energize the intermediate and high fire oil valves. The first switch (AS-1) is actuated to close midway between low and high fire.
This causes the intermediate oil valve to open and the second nozzle to fire, providing an increased firing rate for a smoother changeover between the low and high fire rates and vice versa.
As it moves towards high fire, the air damper allows an increasing amount of air into the boiler. The valve should open at approximately midrange, but definitely at a point when sufficient air is present so that there is no incomplete combustion or smoke
The positioning of the cam must be guided by observing the fire or stack when the valve opens. If smoke or haze is noticed, reposition cam to slightly retard the valve opening
The second oil valve switch (AS-2) should be actuated just as the damper reaches its open position. On the basis of a combustion analysis, damper position or linkage adjustment may be required to provide more or less air at this point.
In the event of damper motor replacement, note position of cams and replace them as nearly as possible to their original position, but be sure to check for proper switch actuation, especially those controlling the oil valves.
If a switch is replaced, make sure that wiring connections are correct. The low fire switch is normally closed while the others are normally open. The setscrew holding the cam should be checked occasionally for tightness.
These valves require no adjustment nor maintenance beyond normal housekeeping. Under normal conditions maintenance and trouble-free operation may be expected. Lubrication is not required.
It is advisable to check at time of the initial starting, and periodically afterwards, for tight shutoff valves.
Despite precautions and strainers, foreign material may lodge under a valve seat and prevent tight closure. As explained in Section 1.7 of Chapter 1, the oil flows through a safety shutoff valve and then through individual valves to each nozzle.
If the flame is not extinguished promptly on burner shutdown, it is an indication that both the safety shutoff valve and the low fire valve are leaking. A smoking condition during low fire operation will indicate that either or both of the high fire valv
A valve may be disassembled for inspection of the seating surface or to check for foreign matter. Care must be taken during disassembly to be sure that internal parts are not damaged during the removal and that reassembly is in proper order.
A low hum or buzzing will normally be audible when the solenoid valve coil is energized.
If the valve develops loud buzzing or a chattering noise, check for proper voltage and clean plunger assembly and interior tube thoroughly. do not use any oil.
Make sure that the plunger tube and solenoid are tight when reassembled. Take care not to nick, dent, or damage the plunger tube.
The coils may be replaced without removing the valve from the line. Be sure to turn off power to the valve.
Check the coil position and make sure that any insulating washers or retaining springs are reinstalled in proper order.
The flame detector should cause a safety lockout upon failure to ignite the pilot, upon failure to light the main flame, and upon loss of flame.
Check each of these conditions as follows to make sure that safety lockout will occur. In the event the safety switch fails to trip and shut down the system on any of the tests, investigate the reason and, if necessary, replace the control or flame detec
Close the gas pilot shutoff cock to prevent ignition of the pilot flame.
Turn the burner switch “on.”
The pilot system will be energized at the end of the pre-purge period. Since no flame is detected, the pilot valve will shut and the main fuel valve(s) will not be energized.
The programmer will complete a cycle including a post-purge and the safety switch will lockout about 30 seconds after the end of the ignition trial.
The safety switch must be reset after allowing a few moments for the thermal element to cool
Reopen the gas pilot shutoff cock.
Open gas pilot cock. Shut the main gas cock or the oil valve in the pump discharge
Turn the burner switch “on.”
Relay 2K should pull in as pilot flame is detected, but the main burner should not ignite.
Relay 2K should drop out within 4 seconds after the main burner ignition period ends.
The safety switch should trip and lock out about 30 seconds after the ignition trial.
With the burner firing in normal operation, shut off the main fuel supply. On a gas fired unit, shut the main gas cock. On an oil fired unit, close the oil valve on the discharge side of the pump.
Within 4 seconds after the flame is extinguished, flame relay 2K will drop out, de-energizing and closing the fuel valves. The programmer will complete its cycle including a post-purge and the safety switch will lockout about 30 seconds later.
The safety switch must be reset after allowing a few moments for the thermal element to cool.
Re-establish main fuel supply.
Valves are factory set and sealed. Change to an existing setting may only be made by the manufacturer or an approved representative.
These valves and their discharge piping must be installed to conform to all applicable codes.
Discharge piping must be supported so that no strain is placed on the valve itself. Proper drainage of this piping should be provided.
Valves with a screwed inlet connection should be threaded into the tapping on the boiler using a parallel jaw wrench. Never use a pipe wrench.
The wrench should be used only on the hex portion of the valve body. No undue strain should be placed on the valve during installation since such strain may cause distortion to the valve seat resulting in a leaky valve.
Do not use a wrench on the valve bonnet. Do not install or remove side outlet valves by using a pipe or level bar in the outlet.
The Model 5 boiler is shipped with a completely installed refractory. This consists of the burner tile, rear access door, and a bed covering the lower drum.
The refractory should be checked for evidence of shipping damage and repairs made prior to initial firing.
Periodic inspection will keep the operator informed of the condition of the refractory. Normal maintenance requires little time and expense and prolongs operating life.
Frequent washcoating of all surfaces is recommended. High temperature, airdry type mortar diluted with water to the consistency of light cream is used for this purpose. Coating intervals will vary with service and are best determined by inspection.
Face all joints or cracks by applying mortar with a trowel or finger tip. Do this as soon as cracks are detected. It is normal for refractories exposed to hot gases to develop thin “hairline” cracks.
This is caused by expansion and contraction. Cracks up to 1/8 inch across may be expected to close at high temperatures. If there are any cracks that are relatively large (1/8” to 1/4”), clean them and fill with high temperature bonding mortar.
The refractory, under normal conditions, will last for considerable periods before replacement is necessary.
In the event of spalling of the furnace floor, remove the affected area and replace with a mix made from regular FurnasCrete (Kaiser).
The burner tiles are precast special shapes and replacements can be ordered from your Cleaver-Brooks representative. Installation is generally done by working from inside of the furnace and through the rear access door. Dry fit all the segments and chip t
Re-install using proper refractory cement. Make sure that all joints are tight and coated with the cement. Mix insulating or cement with refractory mortar and work the mixture into the crevices formed by the back of the tile and the boiler tube panel.
It is important that a good tight seal be attained between the burner housing and the brick. Make sure that the insulating material is in place and cement all joints and crevices. Periodically check the seal and repack as required.
Periodically check the rear door refractory. Make sure that the door bolts and sealing gasket are tight.
