• Introduction
• Users
• Safetyflow fume cupboards
• Fume cupboard types
• Johndec fe2000 fume control system
• Airconserver variable volume control systems
• Service and maintenance

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Airconserver variable volume control systems

FUME CUPBOARD ENERGY SAVER SYSTEM WHICH COMPLIES WITH AS2243.8 AND AS2430.3.
A WHOLE NEW CONCEPT WHICH SOLVES THE OPERATIONS COSTS PROBLEMS ASSOCIATED WITH FUME CUPBOARDS IN AIRCONDITIONED SPACES.

Johndec Engineering Plastics Pty Ltd produce two types of systems:

1. By-pass damper system.
2. Variable speed system.

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The velocity of the air flow across the sash is controlled automatically at all sash positions. All available extraction air passes through the sash opening and across the working area. A substantial improvement on existing systems.

The Airconserver sash allows more efficient air conditioning within the laboratory and improved working conditions for operators.

A "Fan Boost" push button provides the maximum air quantity obtainable from the extraction fan, a safety feature far above that stipulated in the Australian Standards.

The system dispenses with the need for bypass grille or auxiliary supply systems.

Only a single phase 240 volt independent supply is required to air bypass damper and R.S. 485 communications cable between air bypass damper and fume cupboard control panel.

The Airconserver sash systems carries a one year warranty.

Additional safety feature, a protection device is fitted to the Airconserver air bypass damper.

Should the damper be inactivated by power failure or obstructed to disable it to open or close, the L.C.D. will display "Damper Failure" and services to the fume cupboard will not be available, Fan will continue to operate.

Airconserver variable speeed system

The above requirements create two major problems which are well known. Devices have been introduced to overcome these problems but none are completely successful.

Problem No. 1
The average size fume cupboard has a sash width of 1500mm and a fully open sash height of 650mm.

An extraction rate of 488 litres per second is required to achieve the mandatory face velocity of 0.5m/s and to ensure adequate containment as required by the latest standards.

Unfortunately, this extracted air is taken from the conditioned air of the laboratory which has either been cooled or heated in relation to the outside air temperature. This results in a costly waste of energy, which is of course repeated for every fume cupboard with in the laboratory.

Various methods and systems have been devised to overcome this problem, including auxiliary air supply, from a system independent of the air conditioning system, directly into the fume cupboard. To date, however, no completely satisfactory auxiliary air supply system of this type has been devised. It is now recommended in the Standard that these no longer be fitted to fume cupboards as they cause more problems than they solve.

Another application is to provide an auxiliary air supply to the fume cupboard locality within the laboratory, by drawing filtered air from outside the building through an additional air fan and duct.

The Australian Standard comments on the claims for this approach as follows:

"These claims have rarely been substantiated in practice and auxiliary air system have been the primary cause of a number of fume containment problems".

The problems associated with an auxiliary supply system far outweigh the claimed advantages. The problems are: initial capital cost, ongoing operation costs, discomfort to the operations being bathed in a flow of unconditioned air in an otherwise conditioned room, disturbance of air flow in front of the working opening of the fume cupboard, the risk of upsetting the containment value of the fume cupboard and the additional maintenance involved. In addition the buoyancy effect of hot air in summer usually prevents this air from reaching the working aperture of the fume cupboard as well as deteriorating the conditions in the rest of the laboratory.

If an auxiliary air supply system is not used, extra outdoor air must be introduced through the air conditioning system to offset that which is exhausted by the fume cupboard. This results in increased operating costs of the air conditioning system.

Problem No. 2
With the average sized fume cupboard mentioned, an air quantity of 488 litres per second passes through the sash opening when in the fully open position. When the sash is lowered the air velocity through the reduced opening is increased and can reach velocities in excess of 4.0 metres per second.

This has an adverse effect on the work being performed within the fume cupboard, by extinguishing Bunsen burners, blowing away powders and possibly the sucking up of paper, etc., into the extracting system.

The latter have, at times, become lodged in the impeller of the extraction fan, causing a potential hazard by reducing the extraction from the fume cupboard and causing costly maintenance.

In an effort to overcome the problem of high velocities at small sash openings, Bypass Grilles are fitted to fume cupboards; however, they are not a complete answer.

Firstly, it is not feasible to have an area of a Bypass Grille equal to that being covered by the lowering of the fume cupboard sash, consequently high velocities are still obtained when a sash is lowered to the 50mm mandatory minimum opening as dictated by the standards. Secondly, the air passing through the Bypass Grille into the fume cupboard chamber is at high level and this is not always an ideal position to carry away fumes being generated at the workbase.

Thirdly, when work is finished in the fume cupboard and the extraction fan is switched off, any residue, fumes or smells from chemicals stored within the fume cupboard can permeate into the laboratory via the Bypass Grille opening. If the sash is raised to close the Bypass Grille then the fumes would be released through the open sash.

SOLUTION
The Airconserver system overcomes the above disadvantages by maintaining a constant velocity across the fume cupboard sash of 0.5 m/s at all opening positions. This results in an improvement to the standards, since all extracted air will be passing through the sash opening.

Although the fan can be fitted with a 3 phase motor or a 240 Volt single phase motor. This will be an advantage in many cases, where a 3 phase supply is not adjacent to the position of the fume cupboard on site.

A fume cupboard fitted with the Airconserver system does not require a Bypass Grille to overcome the problems of high velocities at smaller sash openings. As all extracted air passes across the work area at the lower sash openings, the minimum extraction rate to dilute any heat or fumes will be lower than that required for a fume cupboard fitted with a Bypass Grille.

One may argue that when the sash is at it's lowest height of 50mm, with a velocity rate of 0.5m/s, insufficient air will be extracted to provide adequate dilution of heat and fumes produced within the fume cupboard chamber.

To overcome this problem, the Airconserver system has a minimum extraction rate below which the cupboard will not fall, regardless of the position of the sash. This minimum point is easily adjustable and can be decided after consultations with the user. It is generally accepted that one complete air change every 12 seconds is sufficient for the average fume cupboard with the sash at it's lowest level.

The Airconserver system comes complete with a special sash sensor connected electrically and mechanically to the fume cupboard sash balance mechanism to synchronise the volume flow of the Air Bypass Damper to the sash opening.

The Airconserver sash system gives immediate response to any sash movement. As an additional feature a "Fan Boost" switch is incorporated in the fume cupboard control panel. Should excessive fumes be generated within the fume cupboard by such things as spillage, exotherms or overheating, the operator by activating this "Fan Boost" switch will bypass the automatic mode and instantly provide the maximum air quantity available from the extraction fan, regardless of the sash position. The extraction rate thus achieved, rapidly clears the fume cupboard of excessive fumes or heat.

The fume cupboard can be immediately returned to it's normal automatic synchronised mode by activating the reset switch fitted in the fume cupboard control panel.

The electronic Airconserver controller is mounted on the Air Bypass Damper in a purposely moulded box with cover. Full indication of operating status is provided by an L.C.D. display on the control unit.

Adjustments are provided within the control unit and are accessible from the front of the fume cupboard to allow settings of minimum and maximum outputs from the Air Bypass Damper. Overload protection is provided within the unit.

All wiring is provided and installed between the sash sensor and control panel "Fan Boost" and "Fan On/Off" provided in the Johndec Fume Control System. Single phase 240 Volt independent supply is required at the Air Bypass Damper and R.S. 485 communications cable between Air Bypass Damper control box and control panel located on the front facia of the fume cupboard.

The Airconserver sash system is manufactured in Western Australia.
The Airconserver system touch panel computer enhances the productivity of the fume cupboard. It is necessary to refer to the user manual, the software driven and controlled L.C.D. & L.E.D. screen constantly shows the actual status of the fume cupboard and indicates the correct action or keystroke required. Faults will also be indicated by flashing L.E.D. audible alarm and L.C.D. screen. The computer provides for the selection for pre or post purge and other operations. It controls the running of the fan, airflow, air boost, spray power, gasses and light.

The menu on the L.C.D. screen guides the operator. No errors can be made! Prevent unauthorised persons from changing the fume cupboard scheduled operation, with the control panel in disable mode. This special code facility is also available to maintenance personnel.

THE AIRCONSERVER ENERGY SAVER SYSTEM ADVANTAGES & SAVINGS

1. The cost of installing the Airconserver sash will be far less than any auxiliary air supply system.
2. The cost savings in energy by the use of this system will far outweigh any initial cost, which could be recovered within the first year of use.
3. The velocity across the sash is controlled automatically at all sash positions. This is an improvement on the Standards as all extraction air will be passing through the sash opening and across the working area.
4. Working conditions are far better for the operator and the air conditioning within the laboratory is also far more efficient.
5. The provision of the "Fan Boost" push button allows maximum performance from the extraction fan to be available at any time and represents a safety feature above that set out in the Standards.
6. Only a single phase 240 Volt independent supply is required at the Air Bypass Damper and R.S. 485 communications cable between Air Bypass Damper and fume cupboard.
7. As the Airconserver sash does not require the use of a Bypass Grille, it disposes of all Bypass associated problems.
8. Noise problems associated with high velocity will be reduced. Apart from the operation of the boost button, the operator has complete control over the local total volume of extracted air by merely raising or lowering the sash.
9. An adjustable volume control damper fitted in the exhaust ductwork is not required when the Airconserver sash is fitted, as the extract air volume is automatically controlled by the position of the sash.
10. The Airconserver System is simple to adjust to any required sash velocity. The operator can readily alter velocity settings to suit new procedures without leaving the laboratory.
11. The Airconserver system can be integrated with an automatic fume cupboard sash. If the fume cupboard is unattended for a specified period of time the "Attendance Sensor" will command the sash to close.
12. The discharge stack velocity will always be maintained at minimum of 10 m/s irrespective of the sash position which conforms to AS2243.8-1992 and AS2430.3-1991, thus allowing the dilution of contaminants contained in the fume cupboard with outside air, thus protecting building from corrosion and protect people working in the near vicinity of such exhaust outlet.
13. The Airconserver system features an additional safety feature. Should power failure occur to the independent supply or the damper obstructed and the damper not fully open or closed, the L.C.D. on the fume cupboard control panel will display "Damper Failure" Services to the fume cupboard will not be available, fan will continue to operate.

EXAMPLE OF SAVINGS

If one takes an average size fume cupboard with a sash width of 1500mm and a fully open sash height of say 650mm, then approximate savings in conditioned air would be as follows.

Sash at Full Height
The sash is usually only raised to it's full height to either clean the fume cupboard or to install or remove equipment from the chamber. In most cases, the extraction fan would not be turned on for this operation. Should the fan be turned on for any reason, then the fume cupboard fitted with the Airconserver sash would behave exactly as a standard fume cupboard. There would be no saving of conditioned air.

Sash at Working Height (Approx. 260mm)
At this working height, the sash is in a position to give full protection to an operators face whilst working at the fume cupboard. The savings in conditioned air at this height would be 263 litres per second or 947m³ per hour.

Sash At Lower Level (50mm)
As a fume cupboard sash spends the majority of it's working life in this position, the savings of the cost of energy over one year are considerable. If we assume that our minimum control on the Airconserver sash was set to give an extraction rate of the chamber of approximately one complete air change every 12 seconds, say 90 m/s on our average sized fume cupboard, then the saving in needlessly extracted conditioned air would be 398 m/s or 1433m3 per hour.

Any of the above savings would, of course, be increased for a larger fume cupboard and multiplied by the number of fume cupboards within the laboratory.

REMEMBER
In this day and age, it is the duty of us all to conserve energy where possible.

Energy is a limited and costly resource, and much time and effort has been expended on systems to effect its conservation.

Where the capital cost of energy minimisation can be quickly covered by operating costs, so please consider the advantages.

AIRCONSERVER VARIABLE SPEED SYSTEM

ALTERNATIVE ENERGY SAVING SYSTEM

The airconserver variable speed system is an alternative to the airconserver modulating bypass damper system.

The system incorporates a variable speed drive connected to exhaust fan motor, which allows the fume cupboard to maintain a constant 0.5m/s velocity of air passing through the working aperture of the fume cupboard regardless of the position of the sash.

The variable speed drive is controlled via sash sensor connected electrically and mechanically to the sash balanced mechanism to synchronise the volume of airflow. A fan boost button is incorporated into the fume cupboard control panel; should excess fumes be generated within the fume cupboard by such things as spillage exotherms or overheating. On activation of this button, maximum air quantity will become available from the extraction fan, regardless of the sash position.

Adjustments are provided within the control unit and are accessible from the front of the fume cupboard to allow setting of minimum and maximum outputs from the fan. Overload protection is provided within the unit.

All necessary internal wiring between the control unit and the Johndec control panel is provided. Terminals are also supplied within the control unit for incoming single phase 240 volt and for 240 volt 3 phase output wiring to a Delta wound 3 phase motor fitted on the extraction fan.

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