The Upward Plenum System. If it is desired to reverse the flow of warmed air, admitting it at the inlets near the floor to pass out near ceiling level, the only way to do this satisfactorily is to distribute the inlets at many points over the floor area, which is seldom convenient except where there is fixed furniture—such as the fixed desks of a council chamber or the fixed, tip-up stalls in a theatre or cinema. When the inlets are well distributed in this way, it is utilized by the occupants in its upward path, and it is then immaterial if it rises up and passes out through open windows or outlet ventilators near ceiling level.
Air Conditioning. This term is generally applied to systems in which, in addition to the fan chamber and heating batteries, there are also two or three other chambers for altering the condition of the incoming air, such as filters, humidifiers and the like. There is no set definition of what air treatment justifies the name. It is just a term and to describe a system which includes more than replacement of vitiated air with warmed fresh air.
The system, as often carried out, provides for propelling into the building, by mechanical means, warmed or cooled, sterilised, filtered, humidified or dehumidified, ozonised and sometimes even perfumed air, which passes along large horizontal ducts and through vertical flues into the rooms, the vitiated air being extracted through other vertical flues leading to a main trunk outlet. The design of such an installation is a matter calling for very great skill and is essentially one for a specialist.
<Callout type="important" title="Critical Design Considerations">The placement of intake vents should be high up, but avoid areas with smoke or soot from chimneys.</Callout>
Air-conditioning Chambers. The fresh-air duct then passes through one of many varieties of humidifying filter, which serves the double purpose of moistening the air and filtering it. Or the filter chamber and the humidifying chambers may be kept separate. It is generally found that only the larger and heavier impurities are intercepted, the finer particles passing straight through.
<Callout type="warning" title="Filter Maintenance">Regular cleaning or replacement of filters is essential to maintain air quality.</Callout>
Principal Types of Filter. Air filters may be divided into four main groups: (a) Wet filters of various types or “air washers”. (b) Dry fabric type filters. (c) Dry “throw-away” type filters, using cotton wool, glass fibre or similar material, on a frame of wire netting or other form, In this case, the filtering medium is discarded as soon as it becomes soiled and is replaced with fresh.
Humidifying Chambers. The humidifying chamber generally takes the form of a mist screen. The general principle upon which this works is usually one of the following: (a) In the vertical intake shaft an arrangement of water jets is provided, these being so arranged as to divide the water finely and distribute it thoroughly over the horizontal area.
<Callout type="tip" title="Humidity Control">Maintaining proper humidity levels ensures comfort and prevents mold growth.</Callout>
The Upward Plenum System. When the plenum system is worked on the “upward” plan, there is danger of short-circuiting the warmed air unless the inlets are thoroughly well distributed about the room.
Key Takeaways
- The Upward Plenum System requires evenly distributed floor-level inlets for effective upward airflow.
- Air conditioning systems include multiple chambers for filtering, humidifying, and dehumidifying air.
- Regular maintenance of filters is crucial to ensure clean air quality.
Practical Tips
- Place fresh-air intake vents high up but avoid areas with smoke or soot from chimneys.
- Maintain proper humidity levels in buildings to prevent mold growth and ensure comfort.
Warnings & Risks
- Improper placement of intake vents can result in poor air quality due to contamination by pollutants.
- Neglecting filter maintenance can lead to reduced air quality and potential health risks.
Modern Application
While the historical techniques described here are foundational, modern advancements have improved efficiency and effectiveness. Today's systems use advanced materials for filtration and humidity control, but the principles of proper ventilation design remain crucial for maintaining healthy indoor environments.
Frequently Asked Questions
Q: What is the Upward Plenum System?
The Upward Plenum System involves admitting warmed air at floor level inlets to pass out near ceiling level. It requires well-distributed inlets across the room to prevent short-circuiting.
Q: Why is regular filter maintenance important?
Regular cleaning or replacement of filters ensures that only clean, filtered air enters the building and prevents health risks associated with poor indoor air quality.
Q: What are the main types of air filters mentioned in this chapter?
The main types include wet filters (air washers), dry fabric type filters, and dry throw-away filters using materials like cotton wool or glass fiber.