Gentek 3980421 User Manual

1.34 Mb

Chapter 6: Maintaining Your Filtered Enclosure

Setting the Inflow Face Velocity with the Speed Control Adjustment

1. Remove the front panel by loosening the (2) Phillips screws on top that secure the front panel.

2. The speed control is located on the electrical subassembly located behind the switched control panel and below the front panel. See Figure 6-1.

3. Adjust the speed control with a small Phillips screwdriver by turning the screw counterclockwise to increase blower speed or clockwise to decrease the blower speed. The speed control is very sensitive, so proceed with caution.

4. Measure the inflow velocity per the averaging technique



outlined in Chapter 3 and adjust the speed control slowly



for the desired speed. Allow the speed to stabilize and re-



measure the inflow velocity to confirm.



5. Replace the front panel and tighten the screws.



Calibrate and Operate the Airflow






Guardian Airflow Monitor (LED Monitor)


Refer to Figure 6-2for operation and calibration.



Labconco Airflow Monitor / Airflow Switch Operation





The Guardian Airflow Monitor (LED) consists of a circuit board



and an airflow switch. This switch indicates airflow as safe or low.



It does not provide an actual face velocity, but a small setscrew in



the back of the sensor can adjust the airflow level that it classifies



as “good/safe” or “low/alert.”



The circuit board provides power to the sensor and also contains a



“safe (green)” and “alert (red)” airflow LED indicators, as well as



a “SILENCE ALARM” button to quiet the audio alarm. When



first powered up, the PCB will light both red and green LED



indicators and sound the alarm to indicate it is working. After 5



seconds, the air monitor will indicate either good or bad airflow



based on what the connected airflow switch detects. For low



airflow, the unit will wait for 10 seconds of bad indications before



it sounds both the audio alarm and the red “alert” LED indicator. If


Chapter 6: Maintaining Your Filtered Enclosure

the “SILENCE ALARM” button is pressed, the audio alarm will be silenced, but the red “alert” LED will remain on. The alarm is silenced indefinitely unless an airflow change is detected. If safe airflow is later detected for 10 seconds, the green “safe” LED will be lit and the “alert” (red) LED will be shut off. At any time the airflow is safe/good, one can press the SILENCE ALARM test button and the audio alarm and the red LED will turn on as long as this button is held down. The PCB has also a two-pinconnector for use as an external output with isolated relay contacts that close when the red/alert LED is lit (low airflow). These relay contacts are not affected by the “SILENCE ALARM” button.

The PCB is mounted behind the front panel using standoffs and an appropriate label is used to highlight the “SILENCE ALARM” button with clear areas for the red and green LED’s. No holes to allow sound to be broadcast louder are necessary.

The PCB can be prepared as a factory special with an additional connector for the following external inputs, and having the following possible functions:

External Alarm allows an external signal to sound the alarm, such as a sash open switch, or a “fail” signal from the building airflow system.

Alarm Disable allows an external signal to prevent a “low” airflow alarm from occurring.

Night Setback allows an external signal to prevent a “low” airflow alarm from occurring (not any different from Alarm Disable above other than the terminology.)

Contact Labconco for ordering information on this special PCB.


1.Ensure the flow switch and alarm circuit board are installed and operational.

2.Allow the enclosure to operate for at least two minutes.

3.If factory installed, the monitor will alarm at 60±10 fpm with the inflow velocity set at 90±10 fpm.

4.To change the factory setting, set the inflow velocity required by your Safety Officer to the desired alarm

condition using the speed control adjustment procedure outlined in Chapter 6.

Once the alarm condition is set, use a small screwdriver to turn the adjustment screw on the airflow switch counterclockwise (facing the screw) until the “low” airflow red LED lights and the audible flow alarm sounds.


Chapter 6: Maintaining Your Filtered Enclosure

5.Adjust the inflow velocity to the nominal operating point required by your Safety Officer.

6.Over time the HEPA filter will load and eventually slow the inflow velocity. Once the alarm condition is met, simply increase the speed control outlined in Chapter 6 or replace the HEPA filter if the speed control is maximized.

7.The table below lists typical alarm conditions based on normal operating conditions. Typical alarm conditions are set at face velocities of 10 to 30 feet per minute below the normal operating conditions due to supply air and exhaust air fluctuations, as well as room air cross drafts. Consult your Safety Officer for proper operating speeds.

Enclosure Operating In-Flow

Alarm Condition Set Point



100 ± 10 fpm


90 ± 10 fpm


80 ± 10 fpm


70 ± 10 fpm


60 ± 10 fpm

50 fpm


Chapter 6: Maintaining Your Filtered Enclosure

Figure 6-2

Guardian Airflow Monitor (LED) with Airflow Switch


Chapter 6: Maintaining Your Filtered Enclosure

Determination of When to Replace Odor Control Carbon Filters and How to Replace

The carbon filters MUST be replaced when anyone of the following two conditions are met:

1.The filtered enclosure outlet (exhaust) concentration approaches the inlet concentration, indicating filter saturation.

2.The odor in the work area becomes intolerable or the concentration of the chemical in the work area is greater than the TWA.

There are four means of determining when its time to change the carbon filters (not shown in the order of preference).

Odor - A person’s sensitivity to odor, tolerance of odor and their comfort level under odoriferous conditions vary with the individual. While odor is an indicator that chemicals are passing through the carbon filter, several points need to be understood:

Odor within the room is not necessarily an indication of saturation or hazardous exposure concentrations.

Odor can be used as a prompt to sample the chemical concentration on the exit side of the carbon filter.

Organic chemicals approved for use in the filtered enclosure have odors that are detectable before reaching the time weighted exposure limits.

Detection Tubes - Color change indicators can be used to measure the concentration of the chemical at the exit side of the carbon filter or in the outlet exhaust. A kit including syringe pump and flexible tubing can be purchased as an accessory from Labconco (Catalog # 6924900). Labconco Customer Service Representatives are supplied with detector tube catalog numbers, as well as telephone numbers to direct you to where to purchase these items.

For Organic, Formaldehyde and Ammonia, chemical specific detector tubes should be purchased when installing fresh filters. Each kit contains instructions on how many strokes of the syringe are required to obtain the stated sensitivity. The sampling syringe is connected to the filtered enclosure exhaust. Connect the syringe to the detector tube while the system is running and pull the air through the tube with the syringe. Each stroke of the


Chapter 6: Maintaining Your Filtered Enclosure

syringe represents a 100-mlsample and corresponds to the number of strokes necessary to give the indicated color changes. Due to the wide variety of organics and varying TWA’s, it is recommended that specific detector tubes be purchased directly from Sensidyne, Draeger or your laboratory supply dealer. Alternate detector pumps can also be purchased from your laboratory supply dealers. The vast majority of detector tubes available start measuring at the TWA. When a user observes a color change in the tube, they should replace the filter immediately. If no detector tube for your specific chemical is available, other means of detection must be used.

Time - For applications that have very consistent inlet concentrations and operating time, “Time” can be used to anticipate saturation or TWA levels based on prior experience. However, this does not replace the need for sampling. Consult Labconco technical specialist for an estimate of carbon filter life based on chemical usage. Detector tubes, or analytical instrumentation shouldalways be used to determine concentrations in the carbon filter. It is recommended that the carbon filters be checked with detector tubes or other means at intervals of 20% of the total estimated filter life. The exception to the 20% recommendation is formaldehyde and any carcinogen or suspected carcinogen. These more hazardous chemicals must be checked at least every 10% of the total estimated time.

Analytical Instrumentation - This is the most accurate means of measuring concentrations ofany chemical. It is the method of choice when no detector tubes are available or the tubes are not sensitive enough to measure at the TWA concentration for the chemical. This method is also to be used to determine saturation when the chemical concentration is below the measurement range of detector tubes.

Odor Control Carbon Filter Replacement Procedure – See

Figures 4-1and4-2for Carbon Filter Replacement.

1.The carbon filters are replaced by first removing the two screws, which hold the clips to secure the upper diffuser screen. Remove the screws, clips and upper diffuser screen.

2.Remove the carbon filter in a careful way to avoid the flow switch and HEPA filter.


Chapter 6: Maintaining Your Filtered Enclosure

3.Re-installthe new carbon filter with the gasket down. Replace the upper diffuser screen, clips and two screws.

4.The weight of the carbon filter with the gasket down will compress the gasket.

Calculating Odor Control Carbon Filter Life

Labconco developed a modeling program to estimate the filter life for typical carbon filters. Since filter life is dependent on the chemical used, the airflow, filter size, and the dwell time, refer to the Chemical Guide for the Paramount® Filtered Enclosure. The estimated life for Odor Control carbon filters for the filtered enclosures is conservatively calculated at 50% or half of the published values for the Paramount in the Chemical Guide. For example, if you use isopropyl alcohol to disinfect and use approximately 100 ml per week during 2 hours of use per day then follow these steps to calculate the concentration in parts per million (ppm).

Steps for Calculating PPM and Filter Life

1.Determine the amount of the proposed chemical lost to evaporation over a given amount of time. For example, if you use isopropyl alcohol and lose approximately 100 ml per week during 2 hours of use per day.

2.Convert the amount lost into ml/min. For this example:

100 ml X

1 week X

10 hours =

100 ml lost

=.17 ml/min


10 hours use

600 minutes

600 minutes


3.Convert ml/min to PPM by multiplying ml/min by the conversion factor found in the second to the last column on the right. For isopropyl alcohol .17 x 41 = 7.0 PPM.

4.Find the PPM value on the chart that comes closest to the value you just calculated in step #3. In this example, round up to 10 PPM, which is close to the calculated 7.0. We may approximate the filter life to be around 155 hours of actual use, but use 50% of this for the Odor Control filters or 78 hours.

5.Insert the estimated filter life into the estimated usage to determine how long filters will last.

78 hours filter life

=7.8 weeks before filter saturation

10 hours per week use



Chapter 6: Maintaining Your Filtered Enclosure

Formaldehyde only

For formaldehyde, use 10% of the impregnated carbon weight. Formalin is 37% formaldehyde by weight. The density of formalin is 1.08 g/ml.



Pounds of

Adsorbed weight of






Volume of


Filter Size





18 x 18 x 1


0.7 lbs./318g

796 ml


30 x 18 x 1


1.2 lbs./545g

1364 ml


42 x 18 x 1


1.68 lbs./763g

1910 ml

Ammonia only

For ammonia, use 10% of the impregnated carbon weight. Assume use of a 50% solution of ammonia for these calculations.



Pounds of







Volume of 50%



II Carbon

Adsorbed weight of



Filter Size





18 x 18 x 1


0.92 lbs./418g

836 ml


30 x 18 x 1


1.35 lbs./613g

1226 ml


42 x 18 x 1


1.89 lbs./859g

1718 ml

Initial Certification

The filtered enclosure has been certified at the factory for an inflow velocity of 90±10 fpm along with the HEPA Filter Leak Test. The filtered enclosure should be certified for the proper inflow velocity required by your Safety Officer. It is also a conservative recommendation to perform the HEPA Filter Leak Test again should there be any damage caused during transport.


Under normal operating conditions, the enclosure should be recertified at least annually if serviced. The certifier should perform the following tests.

Inflow Velocity Test

HEPA Filter Leak Test

In addition, the following tests should also be performed at the user’s discretion:


Chapter 6: Maintaining Your Filtered Enclosure

Measure of Line Voltage and Current

Smoke Test to determine proper airflow patterns

Lighting Intensity Test (when appropriate)

Noise Level Test (when appropriate)

Vibration Test (when appropriate)

Fluorescent Light Replacement

1.Disconnect the power.

2.Locate the small light reflector located under the control panel shown in Figure 6-2.

3.Remove the light reflector support by removing two Phillips screws on the bottom of the light reflector.

4.Rotate and remove the old fluorescent lamp.

5.Reinstall the new fluorescent lamp and light reflector in reverse order.

6.Power the unit up and try the new fluorescent lamp.

UV Light Replacement

1.Disconnect the power.

2.Locate the UV lamp located inside the enclosure.

3.Surface decontaminate the old UV light before handling it.

4.Rotate and remove the old UV lamp.

5.Reinstall the new UV lamp.

6.Power the unit up and try the new UV lamp.

Motorized Impeller Replacement

The motorized impeller must be replaced as a complete unit. When the motorized impeller is replaced, the capacitor may also be replaced. See Appendix A for Replacement Parts Diagram. See Figure 6-5for an isometric view of the motorized impeller plenum assembly. The HEPA filter rests on top of the motorized impeller assembly.

1.Wear appropriate personal protective equipment to decontaminate the filtered enclosure and then unplug from the electrical outlet.

2.Remove HEPA filter per the HEPA filter removal procedure outlined in this chapter.

3.Consult the wiring diagram in Appendix C of the manual and disconnect all the wires of the motorized impeller. Be sure to connect wires on the new motor in the same way the old motor was wired.


Chapter 6: Maintaining Your Filtered Enclosure

4.Remove four screws in the motor bracket that hold motor bracket to the supports with the vibration isolation mounts. Remove the motor and bracket.

!WARNING: High-speedblower. Never operate impeller with housing off.

5.Replace the capacitor with a new one of equal voltage and capacity.

6.Reassemble the new motorized impeller by reversing the assembly steps.

Figure 6-3

Motorized Impeller Replacement