ENERAC POCKET 60
CARBON MONOXIDE ANALYZER
INSTRUCTION MANUAL
Rev.2
October 1996
1. UNPACKING
Unpack the instrument carefully and inspect it for any visible signs of damage. The
Model 60 includes the following:
a. One Model 60 carbon monoxide analyzer.
b. One stack probe equipped with a desiccant filled water trap and disposable
filter.
c. One battery charger.
d. One small screwdriver.
e. One instruction manual.
f. One carrying case.
2. DESCRIPTION
a. PURPOSE AND FUNCTION.
The Model 60 carbon monoxide analyzer is a light weight hand-held meter
that can measure the concentration of toxic carbon monoxide gas with
greataccuracy over the range from zero parts per million (ppm) to 20,000
ppm (2.0%). The instrument has been designed so that it can be used for a
number of different applications. Three of the most significant applications
are listed below:
i. FLUE STACK MONITOR
When the stack probe is connected to the analyzer the instrument
becomes an excellent continuous real time monitor of carbon
monoxide emission in the stacks of boilers, furnaces and the exhaust of
engines. The significance of measuring carbon monoxide
concentrations as a means for tuning boilers for maximum efficiency is
well known. Maintaining a certain very small amount of carbon
monoxide in the stack is the best way to ascertain that a boiler is
operating at its peak efficiency.
ii. AREA SAFETY MONITOR
Carbon monoxide gas is present in many work areas. It is a highly
toxic, odorless and colorless gas and exposure to high concentrations
can be lethal. The analyzer operating on the diffusion mode is an
excellent monitor against build up of carbon monoxide gas. A dual
audiovisual alarm warns people when concentrations excced a preset
limit.
iii. DUAL PURPOSE METER
When a hose is connected to the analyzer input, the instrument can pull
gas samples from any closed or difficult to get compartment. If the
analyzer is switched to its cycling mode, the instrument can
"simultaneously" monitor gas concentrations in remote compartments
such as a stack and also in the area where the analyzer is located.
b. OPERATING PRINCIPLES
i. POWER REQUIREMENTS
The instrument is powered by six "AA" rechargeable Nickel Cadmium
batteries. Battery life is 10 hours of continuous operation with the
pump running, or 30 hours of continuous operation with the pump off.
The rechargeable batteries can be recharged by plugging the AC
charger to an suitable 115 VAC, 60 HZ outlet (220-240 VAC for
export units) and letting the batteries charge overnight. The battery
charger may also be used to run the Instrument continuously from an
AC source without depleting the batteries. When the battery is
discharged (i.e., the voltage drops below 5.5 volts) the display will
blank. This is an indication that the batteries need recharging.
ii. GAS FLOW DESCRIPTION
The instrument houses an electrochemical sensor which converts the
concentration of carbon monoxide to a millivolt signal. The relation
between concentration and voltage is linear. The sensor is highly
specific to carbon monoxide. Hydrogren and hyrogen sulfide are the
only two common gases that interfere (i.e., the sensor will respond to).
It is not affected by relative humidity and its sensitivity to temperature
variations is minimal over the range from zero degrees celcius to 40
degrees celcius. It's expected life is 1-2 years. The sensor is mounted
on a thin aluminum housing that has two openings, one to the pump
and the other to the diffusion input on the side of the instrument. If the
sensor is exposed to a large concentration of carbon monoxide gas
(exceeding 20,000 ppm or 2.0%) it will saturate. The display will
indicate overrange. If the source of carbon monoxide is then removed,
the display will still indicate overrange for a few minutes depending on
the concentration of CO gas and duration of exposure. Once the excess
CO has been consumed by the sensor, the display will give normal
readings. The sensor will be not be permanently damaged by high
concentrations of CO.
iii. SAMPLING MODE (PUMP ON).
With the stack probe (or any other hose) connected to the stack input of
the instrument, a gas sample of approximately 1000 cc/min is drawn by
the pump through the probe which includes the fiber filter and water
trap, whose respective functions are to trap soot particles and remove
condensed water and water vapor. The gas sample is drawn by one
small rugged gas pump that is operated by a high quality motor. It is
then introduced into the housing that contains the carbon monoxide
sensor and exhausted through the diffusion port on the side of the
instrument.
iv. DIFFUSION MODE
When the pump is not operating, gas simply diffuses past the stainless
steel screen of the diffusion input and into the housing where the
sensor is located. The length of the diffusion path is only about 1/4
inch.
v. CYCLING MODE (PUMP CYCLES ON AND OFF)
In the cycling mode, gas enters the sensor cavity alternatively from the
stack input (when the pump is operating) and from the diffusion input
(when the pump is not operating).
3. OPERATING CONTROLS
a. ON - OFF SWITCH
This is a two position slide switch that must be pushed upward to operate
the instrument. When charging, the batteries this switch must remain in the
OFF position.
b. PUMP MODE SELECTOR SWITCH
This is a three position slide switch that controls the operation of the pump.
When the switch is in the uppermost position the pump will run
continuously and gas flow takes place from the stack input toward the
diffusion port. When the switch is in the bottom position, the pump is not
operating and the gas enters the sensor housing only from the diffusion
input. When the switch is in the middle position the pump will operate
intermittently as follows:
It will run for approximately 2 minutes (with the exception that the pump
will operate for 4 minutes during the first cycle), then it will turn off for
approximately 25-30 minutes, it will then run again for 2 minutes, shut off
for 30 minutes and so on.
c. ALARM LEVEL SWITCH
This is a three position slide switch that allows setting of the audio & visual
alarm to one of three different levels. When the switch is in the bottom
position, the alarm will turn on when the carbon monoxide level detected by
the sensor exceeds 50 ppm. (It will turn off when the level drops below 42
ppm). This alarm position should be used for safety purposes.
When the switch is in the middle position the alarm will turn on when the
CO concentration exceeds 200 ppm. (It will turn off when the level drops to
190 ppm). A Carbon Monoxide level of 150-200 ppm is usually considered
the point where efficiency of a boiler is maximum.
The top position of the switch sets the alarm at 400 ppm. This is the
maximum level allowed by certain regulatory agencies.
d. BUZZER SWITCH
This is a tiny slide switch that turns on or off the sound alarm. It is
convenient to use when testing the instrument or when the sound of the
buzzer is not necessary.
e. THE DUAL RANGE SWITCH
This switch selects the operating range of the analyzer. There are two
ranges: 0-2000 PPM and 0-20,000 PPM. If you are not sure of the carbon
mopnoxide concentration of your source, always turn the analyzer on with
the range switch set in its upper (20K PPM) position. For accurate low
concventration readings set the range switch to the lower (2K PPM)
position.
NOTE: We strongly recommend that the analyzer not be exposed to
concentrations exceeding 5000 PPM for more than a few minutes to prevent
gradual sensor saturation.
4. INSTRUMENT OUTPUTS
a. DISPLAY
This is a 3-1/2 digit, 0.5 inch high liquid crystal display that indicates the
concentration of carbon monoxide in parts per million (ppm). When the
range switch is in the lower position, resolution is 1 PPM. When the range
switch is in the upper position, the display reads in thousands PPM and its
resolution is 10 PPM(0.01%). If the display’s range is exceeded, a one
followed by blanks will be displayed. A blank display functions as a low
battery indicator.
b. OUTPUT JACK
This is a convenient miniature jack output for use with a recorder or for
remote measurements of carbon monoxide concentration. Output is linear
and corresponds to 1 volt per 1000 ppm of carbon monoxide (range switch
in the lower 2K position) and 1 volt per 10,000 PPM (range switch in the
upper 20K position).. It can be connected to any instrument with an
impedence of 100 ohms or higher.
c. ALARMS
There is one audio and one visual alarm. The audio alarm is a continuous 2
KHZ tone. The visual alarm is a flashing red light located on the face of the
casing. The alarm will turn on at the level selected by the alarm switch.
5. OPERATION
a. START UP PROCEDURE
Remove the instrument from its case. If the unit is to be used for stack
measurements, take the probe and make sure that there is no liquid water in
the water trap, that the desiccant is blue in color, and the disposable filter is
clean. Connect the probe to the instrument. Set the pump mode selector
switch to the desired position. Turn the instrument on. The display will
come on and you will notice a quick increase in the display reading followed
by a gradual drop to zero in about 30 seconds. If the display reading does not
go back to exactly zero and you are in clean atmosphere, the small
screwdriver can be used to make the necessary adjustment by rotating the
zero adjustment potentiometers. There are two separate zero adjustments.
Set the range switch to the upper position and zero the display using the
20K zero adjust potentiometer. Next set the range switch to its lower
position and zero again the display using the 2K adjust potentiometer.
Now the instrument is ready to take measurements.
b. STACK MEASUREMENTS
To measure the carbon monoxide concentration in the flue stack, set the
pump switch to the ON position. You should hear the pump running.
If you don’t know the approximate CO concentration, or if you are
measuring engine exhaust set the range potentiometer to its upper (20K
PPM) position.
Insert the stack probe into a 5/16 inch diameter hole in the stack and push
the probe so that its tip is as near as possible to the center of the stack. The
instrument can be held in the hand, or if it is desired to make adjustments to
the furnace or boiler, use the instrument handle to hang it from any nearby
convenient protrusion that is not hot to the touch, or to decrease the viewing
angle when the instrument is placed on a flat surface. MAKE SURE THE
INSTRUMENT OR HOSE IS NOT IN CONTACT WITH A HOT
SURFACE! (A surface that is too hot to touch).
To monitor the carbon monoxide in the stack on a 24 hour basis, set the
pump switch to the cycle position. Keep in mind that the water trap may
become filled up and the disposable filter may require replacement after 4-5
hours of continuous operation in the stack. Consequently, if the instrument
is operated in the cycling mode, the filter and water trap must be checked
once each day. In addition, the instrument will have to operate with the
battery charger connected to a 110 volt AC source after the first day of
operation.
c. AREA MONITORING
NOTE: The instrument is not designed to be intrinsically safe and
should not be used in explosive atmospheres!!!
The instrument may be used as a safety device for the detection of
hazardous carbon monoxide gas for work areas. Do not connect the probe to
the instrument. Set the pump switch to the OFF position. Set the range
switch to its lower (2K PPM) position. Set the alarm switch to the 50 ppm
position. You may hang the instrument from any convenient place or carry it
with you. If you wish to take a quick "sniff" of a suspected area, turn on the
pump, wait 30 seconds. If the instrument is operated on a 24 hour
continuous basis, the pump may wear out after 4-6 months.
d. SHUT DOWN PROCEDURE
When you are finished using the instrument, make sure the power switch is
turned off. If you have used the stack probe, do not touch the metal tubing
until it is cool.
Remove any water from the water trap, turn the probe upside down and
shake it well and get rid of the condensed water.
Give the instrument batteries a fresh charge.
6. MAINTENANCE
a. CLEANING THE WATER TRAP
The water trap is made of two compartments. The first compartment is
intended to catch all moisture that has condensed in the probe. The second
compartment is filled with a dessicant material (#44 silica gel) that will
adsorb the remaining water vapor in the stack gas. The dessicant is colored
deep blue when dry. As it absorbs moisture its color changes progressively
to dark pink and eventually to pale pink when it is completely used up.
There is sufficient desiccant material in the trap for approximately four
hours of continuous operation. When the desiccant is used up it must be
replaced, otherwise moisture will eventually penetrate through the filter and
will be deposited on the surface of the sensor. This may cause erratic or low
readings.
Used up desiccant material can be reactivated by heating at 300-400 degrees
Fahrenheit in a clean atmosphere for about one hour until it becomes blue
again. Because of possible soot collection, however, it may be impractical to
reactivate the dessicant more than two or three times.
Extra desiccant material is available from the factory. It is supplied in one
pound containers.
To replace the desiccant material, simply pull out the plastic plug (caplug).
Fill the silica gel compartment with new material and force the plastic plug
back over the clear tube until an airtight seal is obtained. Liquid water which
has accumulated in the first compartment can be removed by simply pulling
out the caplug at the other end of the water trap, pouring out the liquid and
replacing the plug.
b. CHANGING THE DISPOSABLE FILTER
The disposable filter needs periodic replacement. It must be replaced it is is
noticeably discolored, or if the pump fails to operate, indicating a blockage
in the line. The disposable filter must always be connected so that the
direction of flow is radially inwards (towards the center). This allows the
operator to more eaily notice discoloration of the filter and any moisture that
penetrates through the water trap. To replace the filter, simply loosen the
two clamps that secure it to the hose. Take a new filter and connect the two
ends of the tubing to it, observing the correct direction of flow. Fasten the
clamps.
c. REPLACING THE CARBON MONOXIDE SENSOR
This is a very infrequent procedure since the carbon monoxide sensor has an
expected life of 1-2 years. The CO sensor needs replacement when it is no
longer possible to calibrate the instrument using calibrated gas.
To replace the sensor, remove the four screws that secure the base and
expose the interior to the instrument. The sensor is the 1-1/2 inch round
plastic disk that is attached to the back of the aluminum housing. Remove
the screws that hold the sensor (the CO sensor contains sulfuric acid,
exercise caution). Attach a new sensor to the housing. Remove the short
between the sensor terminals and connect the wires to the sensor, observing
the correct color code. Carefully, close the case, making sure that no wires
or tubing are being pinched. Secure the case with the four screws.
7. INSTRUMENT CALIBRATION
The Model 60 Carbon Monoxide Analyzer has been calibrated at the factory by using
a calibrated gas that contains 200 ppm carbon monoxide in air (range switch in the
lower position). (However, any other calibration gas in the range of 50-2000 ppm CO
in air or nitrogen can be used, if available. Higher concentration may be used with the
range switch set in its upper position ). The sensor possesses good stability and does
not require frequent calibration.
A tentative recommended calibration schedule is as follows:
If the unit is used in engine exhausts, calibrate after 10- 20 hours of use. If the unit is
used in boilers calibrate every one or two weeks. If the unit is used for area
monitoring (safety) calibrate every 3-4 months.
If it is desired to check the calibration of the instrument, connect the probe to the
instrument and turn on the instrument. Turn on the pump. Wait two minutes and
carefully zero the instrument, making sure the air the instrument draws is clean and
free of any smoke or exhausts.
If you are using the ENERAC calibration kit follow the directions in the calibration
kit manual.
If you are using your own span gas, feed the calibrated gas to the stack probe at a rate
of approximately 1000-1500 cc/min. Use a flow meter to observe the flow into the
instrument. Listen to the sound of the pump. Adjust the flow rate between 1000-1500
cc/min. so that the sound of the pump appears normal as when it was aspirating air.
Wait till the CO reading of the display has stabilized. If you are using high
concentration span gas, make sure the area is well ventilated, or carry out the
calibration under a fume hood, since carbon monoxide gas is highly toxic. Remove the
small round black plastic cap that covers the span adjustment potentiometer. With a
small screwdriver, rotate the span adjustment potentiometer until the display indicates
the correct reading. Replace the black plastic cap. Shut off the gas, disconnect the
probe, and wait 3 minutes and make sure that the display reading goes back to zero.
8. THE SIGNIFICANCE OF CO GAS
Carbon monoxide is a colorless, tasteless, odorless gas. it is slightly lighter than gas. It
is almost always found as a by-product of incomplete combustion. Carbon monoxide
burns in air or oxygen to form carbon dioxide. The blue flame observed over a coal
fire is carbon monoxide burning to carbon dioxide.
Carbon monoxide is a direct and cumulative poison. It combines with the
haemoglobin of the blood to form a relatively stable compound, carbony-haemoglobin,
which makes the blood useless as an oxygen carrier. When about one third of the
haemoglobin was combined, the victim dies. The gas is one of the most treacherous
poisons because of its odorless character and insidious action. A concentration of 100
ppm of carbon monoxide in air produces symptoms of poisoning while a concentration
of 1500 ppm (0.l5%) will cause death in thirty minutes. The permissible levels for
work areas, as specified by OSHA, are 50 ppm on a time weighted 8 hour day with a
maximum allowable concentration of 400 ppm.
Carbon monoxide in the home may come from a leaky furnace or red hot kitchen
stoves or heaters when the draft is closed. In the workplace, it is often the result of
operation of internal combustion engines, where exhaust may contain from 1% to 8%
(80,000 ppm) carbon monoxide, due to incomplete combustion. It has been estimated
that a 20 horsepower engine produces one cubic foot/minute of the gas. In a small
closed area, such as a garage, the atmosphere becomes deadly in 5 minutes if the
engine is left running. A person breathing this atmosphere becomes helpless before
realizing the danger. Even outdoors, in crowded city streets, the carbon monoxide
concentration may approach the danger level.
Since carbon monoxide is the product of incomplete combustion in a furnace, it
becomes an excellent mechanism for reducing the excess air until incomplete
combustion begins to take place. For most well functioning industrial burners or
furnaces, a carbon monoxide concentration in the range in the range of 100-200 ppm
usually coincides the maximum boiler efficiency and therefore maximum fuel savings.
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