Official websites use. Share sensitive information only on official, secure websites. The air distribution system up to the VAV boxes shall be medium pressure and shall be designed by using the static regain method.
Downstream of the VAV boxes the system shall be low and medium pressure construction and shall be designed using the equal friction method. Sound lining is not permitted. Double wall ductwork with insulation in-between is permitted in lieu of sound lining.
All VAV boxes shall be accessible for maintenance. Ducted return shall be utilized at all locations. VAV fan-powered box supply and return ducts shall have double wall ductwork with insulation in-between for a minimum distance of 5 feet.
Underfloor Air Distribution Systems. Provide plenum zones both for perimeter and interior in order to control the underfloor variable volume dampers or boxes with separate plenum barriers between perimeter and interior zones.
The underfloor plenum shall be air tight and compartmentalized with baffles. Provisions shall be provided for cleaning the plenum space. When underfloor supply air distribution is used, the ceiling plenum shall be used for the distribution of the ducted return air. The perimeter and interior underfloor zones shall be clearly separated in order to maintain proper pressurization, temperature and humidity control. Zoning of the underfloor air distribution systems shall be in accordance with descriptions presented elsewhere in this chapter.
Perimeter wall below the raised flooring system shall be provided with R insulation and vapor barrier below the raised floor. All VAV boxes that are part of an underfloor air distribution system for both perimeter and interior systems shall be located below the raised floor. The floor area used for an underfloor system shall have the slab provided with a minimum of R insulation and vapor barrier from below.
This shall incorporate the entire slab area used for the underfloor system. Volume Control. Particular attention shall be given to the volume control. VAV systems depend on air volume modulation to maintain the required ventilation rates and temperature set points.
Terminal air volume control devices are critical to the successful operation of the system and shall be provided.
Zone loads must be calculated accurately to avoid excessive throttling of air flow due to oversized fans and terminal units. Diffusers shall be high entrainment type minimum to maximize air velocity at low flow rates. If ventilation air is delivered through the VAV box, the minimum volume setting of the VAV box should equal the larger of the following:.
VAV terminal units must never be shut down to zero when the system is operating. Airside Economizer Cycle. Enthalpy economizers shall operate only when return air enthalpy is greater than the outside air enthalpy. All ductwork joints and all connections to air handling and air distribution devices shall be sealed with mastic— including all supply and return ducts, any ceiling plenums used as ducts and all exhaust ducts. Click here to sign up. Download Free DOC.
Download Free PDF. Method statement for HVAC air distribution system installation. Ashique KP. A short summary of this paper. In order to combat the declining trend, strategy and vision, NMC has decided to build their new unit in Dubai Investment Park and appointed A to Z as a consultant. Plumbing scope: Domestic and drain piping Fire system scope: sprinkler, fire suppression, fire alarm ….
Electrical scope: HVAC control panel, BMS, fire alarm control panel, normal lighting, emergency lighting, lighting distribution board, cabling, Junction boxes, switches and sockets. In case of any change in any product, Scope of work or specification at a later stage, necessary updating to be carried out relevant sections of this method statement with reference to corresponding manufacturer instructions. This Method Statement covers all the critical installation activities of systems within the scope of work.
Need to identify a safe and clean designated storage shelter if the material needs to be stored at site prior to installation on its final location. Material need to be properly stacked on pallets and preserved as per the manufacturer instructions. Check, manufacturer protection is sufficient enough for the storage and transportation and if required, provide additional protection. Any flammable material and chemicals shall be stored as instructed by Material Safety Data Sheets.
Material safety data sheet MSDS shall be kept at easily accessible location of the storage spaces containing chemical solvents, powders etc.
All the material shall be preserved based on the manufacturer recommendation. Material inspection shall be carried out by QC personnel. Storage area shall be barricaded and labeled properly.
Entry into this area shall be restricted to authorized persons only. Critical material handling activity shall be done in presence of Modular safety officer and the concerned supervisor. Dismantling and modifications also shall be done by as per site requests. There are many other important positions directly or indirectly involves in this project may not be appearing in the list below. He is directly reporting and discussing the project plans, issues, progress etc. He ensures that the work is executed as per project specifications and project quality requirements.
The experiments were carried out in a well-insulated environmental chamber 5. Three workstations WS were established so that three subjects could be tested at the same time.
Custom-build displacement diffusers were positioned behind the subjects at minimum distance of 0. The subjects were allowed to move their feet within a marked area of 0. The subjects were instructed to keep the feet flat on the floor throughout the tests.
A dedicated spot cooling system supplied conditioned air through the three diffusers while an underfloor air system was used to keep the whole space at a desired room temperature.
Air temperature was measured at heights of 0. The air temperatures were monitored continuously using thermistors. The measured air temperatures and velocities at the feet are reported in the x-axis of Figure 1.
Each test took 3 hours. At the beginning of each test, the subjects sat for 30 minutes in a mesh chair to let their body to adapt to the chamber temperature.
After this preconditioning time, the subject sat on the chair under the influence of the diffuser for 30 minutes and then rested outside the influence of the jet for 30 minutes. Subjects were allowed to adjust their clothing to keep their whole body thermal sensation neutral during the entire duration of the test, but they were not allowed to change their clothing in the lower part of the body during the test. A survey was given before and after 1, 5 and 27 minutes measured from the start of each test condition.
The survey questionnaires include six parts: 1 overall thermal acceptability; 2 thermal comfort, thermal preference, and thermal sensation on a 7-point ASHRAE scale; 3 air movement acceptability at ankles and preference; 4 thermal sensation at the hands, torso, ankles and feet; 5 air movement acceptability at hands, torso, ankles and feet; and 6 air quality acceptability.
The temperature at the ankle was different at each workstation, varying with the supply air setpoint and air speed. In Figure 1 is shown the overall thermal acceptability vote at the end of each test. Between 20 and 37 percent of the subjects found the thermal environment not acceptable. The number of dissatisfied subjects is higher than expected.
0コメント