2.1 Ducts and Pipes Sizing and Insulation Specification 2.5.1 Duct Size Calculation
2.1 Ducts and Pipes Sizing and Insulation Specification 2.5.1 Duct Size Calculation
2.1 Ducts and Pipes Sizing and Insulation Specification 2.5.1 Duct Size Calculation
Supply, Extract, and Exhaust ducts were sized using the equal friction
method. The most economical and simple way of calculating duct sizes
and duct external static pressure (ESP). “Equal friction” does not mean
that total friction remains constant throughout the system. It means that a
specific friction loss or static pressure loss per 100 equivalent feet of duct
is selected before the ductwork is laid out and this loss per 100 feet is
The suggested friction loss shall be 0.10 in.wg per 100 ft. (SMACNA 3rd
Note: Solving for Supply, Extract, and Exhaust Duct Sizes, refer to list
of duct layout drawings and with the use of SMACNA Duct Friction
Loss Chart.
fan size and motor power input. Duct ESP includes pressure drop from
The total duct static-pressure loss due to friction for a duct system can be
calculated from:
hf = ff x L
where:
accessories
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2.5.3 Chilled Water and Drain Piping
Pipework for chilled water shall be heavy grade mild steel with screwed, welded or
flanged fittings, valves, etc. Piping of 100 mm diameter and larger shall be flanged.
Valves 29 mm and smaller shall be forged brass body, diaphragm type, packless
globe valve with solder ends. Valves 35 mm and larger shall be bronze alloy, non-
rotating disk, nylon seats, bolted bonnet globe valve with solder ends. Condensate
piping shall be cast iron screwed drainage fittings, insulated. All condensate drains
from air conditioning equipment shall be trapped and vented with condensate drain
be piped and drain to the sanitary sewer system. An alternate method shall be to
terminate condensate drain piping at outdoor dry-well type sumps where condensate
dry pipe after all testing is completed and approved. Pipe insulation shall be heavy
density rigid fibreglass with factory applied vinyl coated embossed foil vapour
barrier laminate jacket with pressure sealing lap adhesive. The insulation shall be
shall have a minimum thermal resistance (R value) of 1.46 meter-degree Kelvin per
watt. Pipes outside the building shall be insulated with minimum 25 mm thick
Chilled water pipework, valves and fittings outside the buildings shall be insulated,
and fitted with vapour-proof covering with external mechanical and weatherproof
covering.
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2.5.5 Ductworks and Insulation
All material used in fabrication of ducts, plenums, stiffeners and supports shall be
new galvanized steel. Sheet metal shall be galvanized sheet metal with a minimum
zinc coating of 275 grams per square meter where used indoors. Where the sheet
metal is to be used for ductwork for fresh air ducts located indoors and all ducts
located outdoors additional protective powder coating shall be used. Ducts shall be
Duct insulation in all air conditioned space shall be 25 mm thick rigid slab of
fiberglass with density of not less than 48kg/m3. Duct insulation which is located
Ductwork insulation shall be fixed to the duct with approved fire resistant adhesive
and where necessary the adhesive shall be reinforced with nylon duct clips and
washers of approved manufacturer. Insulation section will be closed butted with butt
Cavities in the ductwork insulation surface will be filled and sealed with an approved
vapour sealant.
The surface finish of the ductwork shall be 8 ounce canvass applied using vapour
barrier mastic and full coat of lapping cement then a second coat of lapping cement
over entire canvass surface. (Use aluminium cladding outdoors, and indoors where
After the load is evaluated, the equipment must be sized with the capacity sufficient to
offset this load. The air supplied to the space must be of the proper conditions to satisfy
both sensible and latent heat load estimated. Equipment selected is designed to operate
efficiently at high ambient condition. The equipment manufacturer should abide and
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2.6.1 Air Handling Units
Air Handling Units Sizing (See the following calculation sheets below that is
1. MANUFACTURED UNITS
2.6.3.1 Chilled and Condenser Water Pumps Sizing (Refer to sample calculation
CALCULATION TABLE-16
Total Head Loss of Pump
HP = 35.81
NEXT CAPACITY TO BE
SELECTED
40 HP EACH CHILLED WATER
PUMP
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2.6.3.2 Chilled and Condenser Water Pumps Specifications
1. PUMPS, GENERAL
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2.6.4 Cooling Towers
Base
Construction
A) Except where otherwise specified, all components of the cooling tower
shall be fabricated of heavy-gauge steel, protected against corrosion by G-
235 galvanizing. The tower shall be capable of withstanding water having
a pH of 6.5 to 8.0; a chloride content (NaCl) up to 300 ppm; a sulfate
content (SO4) up to 250 ppm; a calcium content (CaCO3) up to 500 ppm;
silica (SiO2) up to 150 ppm; and design hot water temperatures up to
125°F.
B) The specifications, as written, are intended to indicate those materials
that will be capable of withstanding the above water quality in continuing
service, as well as the loads described in paragraph. They are to be
regarded as minimum requirements. Where component materials peculiar
to individual tower designs are not specified, the manufacturers shall take
the above water quality and load carrying capabilities into account in the
selection of their materials of manufacture.
Mechanical Equipment
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A) Fan(s) shall be propeller-type, incorporating wide-chord aluminum
alloy blades and galvanized hubs. Blades shall be individually adjustable.
Maximum fan tip speed shall be 13,000 ft/min. Fan(s) shall be driven
through a right angle, industrial duty, oil lubricated, geared speed reducer
that requires no oil changes for the first five (5) years of operation. The
gearbox bearings shall be rated at an L10A service life of 100,000 hours or
greater. An external oil level dipstick shall be located adjacent to the
motor at the fan deck surface and shall be accessible from a portable
maintenance ladder.
B) Motor(s) shall be 40 hp maximum, TEFC, 1.15 service factor, variable
torque, and specially insulated for cooling tower duty. Speed and electrical
characteristics shall be 1750 RPM, single-winding, 3 phase, 60 hertz, 460
volts. Motor shall operate in the shaft-horizontal position, and nameplate
horsepower shall not be exceeded at design operation. VFD Controller
shall be used and BMS controlled and monitored.
C) The complete mechanical equipment assembly for each cell shall be
supported by a rigid steel structural support that resists misalignment
between the motor and the gear reducer. The mechanical equipment
assembly shall be warranted against any failure caused by defects in
materials and workmanship for no less than five (5) years following the
date of tower shipment. This warranty shall cover the fan, speed reducer,
motor, drive shaft and couplings, and the mechanical equipment support.
A) Two open basins (one above each bank of fill) shall receive hot water
piped to each cell of the tower. These basins shall be installed and sealed
at the factory, and shall be equipped with removable, galvanized steel
covers capable of withstanding the loads described in paragraph.
B) The water distribution system shall be accessible and maintainable
during tower fan and water operation.
C) Each cell of the tower shall include a single hot water inlet connection
located as shown on the plans. An internal system of piping shall deliver
water equally to the distribution basins without the need for balancing
valves. This internal piping system shall require no scheduled
maintenance, and shall be located such that it does not interfere with
normal maintenance access. The internal piping must extend to the tower
exterior. Removable, interchangeable polypropylene nozzles installed in
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the floor of these basins shall provide full coverage of the fill by gravity
flow. Heavy-duty flow-regulator valves shall be provided at the hot water
inlet connections. These valves shall be disc-type, with cast iron bodies
and stainless steel operating stems. There shall be a locking handle to
maintain the valve setting in any position. Valves shall be right angle
configuration, precluding the need for inlet elbows.
D) The water distribution system shall be accessible and maintainable
while tower is operating.
Design Loading
A) The casing and fan deck shall be heavy-gauge galvanized steel, and
shall be capable of withstanding the loads described in paragraph 4.1. The
top of the fan cylinder shall be equipped with a conical, non-sagging,
removable fan guard, fabricated of welded 5/16" and 7 gauge rods, and hot
dip galvanized after fabrication. Fan cylinders 5'-0" in height and over
shall not be required to have a fan guard.
Access
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Cold Water Collection basin
Fan Coil Units (FCU) are sized up according to the total sensible heat gain of
each room and calculated air flow to offset the sensible heat gain. The air flow
(CFM) and total BTUH are mostly to be considered in sizing the FCU.
2.6.5.2 Fan Coil Units Specifications
The proposed Fan Coil Units (FCU) shall be heavy duty type and should
be suitable for extreme weather conditions like here in Saudi Arabia where
they are intended to be used. Equipment selected shall comply with
ASHRAE Standard 90.1 and performance is rated in accordance with ARI
Standard 550/590. The FCU shall be consisting of rigid galvanized steel
casing, copper tube/aluminum fin coil type heat exchanger, fan board
assembly, manual coil air vent with drain pan, junction box with terminal
strip.
FCU motors shall have internal thermal temperature cut-out above 140°C
with permanent split-capacitor, three-speed, tap wound, induction type for
maximum efficiency. Motors shall have permanently lubricated ball
bearings and all-direction, vibration isolating mountings to ensure
vibration free operation and minimum noise. Motor wiring shall be
enclosed by flexible metal conduit and connected to the junction box.
The material of fan wheel shall be galvanized steel and mounted directly
onto each shaft. The DIDW centrifugal fans shall have balanced and
forward curved blades. Fan housings shall be made of galvanized sheet
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steel. The fan board can be simply removed by loosening the fasteners for
easy service purpose.
The FCU drain pan shall be 25mm depth with 0.8mm thickness galvanized
steel coated with internal epoxy resin coating. The drain pan shall be one-
piece stamped processed seamless and no joint to avoid leakage.
Insulation material shall be 5mm thickness, 27 kg/m3 density PE foam.
The drain pan shall have one 3/4-inch male pipe thread (JIS B 0203-1966)
connection.
Its Performance ratings shall conform to AMCA standard 211 and 311 and
must be tested in accordance with ANSI/AMCA Standard 210-99 and
AMCA Standard 300-96 in an AMCA accredited laboratory. Fans shall be
certified to bear the AMCA label for air and sound performance seal.
Exhaust fan shall be either direct mounted, isolated with housed spring or
as per requirement on the equipment schedule or drawings.
Air handling units shall be installed with sufficient room to allow the
installation of all control components. Allow sufficient space around the
unit for removing the access panels and various parts of the unit. A
minimum clearance equal to the width of the unit must be provided on one
side of the unit for removing the coil or fan assembly and other
accessories. Add dimension of pipe chase, air hoods, ducts,
control/electrical panels, etc. to minimum clearances. Allow additional
clearance as required by local and national codes.
Unit must be installed on flat and level surface. Units must be installed in
such a manner as to provide enough elevation for properly designed
condensate traps. Condensate drain shall be properly trapped.
Ensure that all power and field wirings are installed, tag, and harnessed
properly.
Air Handling Units shall be installed complete with all accessories and
controls to operate as per design intent and project specifications.
All AHU shall be installed with due consideration for operation and
maintenance activities to be undertaken by the maintenance staff later on.
All AHU machine connections such as but not limited to piping, duct,
electrical, condensate drain shall be plumb, level, slope, supported,
anchored and shall have flexible connections as required.
Install chillers on 4-inch thick concrete base, 4 inches larger on each side
than base of unit. Anchor chillers and vibration isolators to concrete base.
Label the amount of refrigerant in the system and also the name and
pressure of refrigerant used.
Wire chillers so it cannot start unless chilled water and condenser water
circulating pumps are running and shall be controllable and monitor via
BMS.
All piping is installed and supported and the direction of flow shall be
indicated in accordance with the approved specification and drawings.
Gages shall be installed as required to establish design flow for the cooler
and condenser.
Pump shall be located in a clean, dry area free from flooding. The area
shall provide adequate space for operation, maintenance, inspection and
repair, considering complete disassembly and handling of equipment. The
pump shall have a supply of clean liquid for packing or mechanical seal
lubrication. The pump shall be positioned to provide the most efficient
pipeline system.
Pump and drive motor shall be installed completely align (angular &
parallel) to avoid unintended contact of rotating parts and prolong pump’s
life.
Piping connected to the pumps shall be supported and meets the Hydraulic
Institute, ASME/ANSI, DIN requirements in conjunction with
construction documents and specifications.
Use of elbows close to the pump suction flange shall be avoided. There
should be a minimum of two pipe diameters of straight pipe between the
elbow and suction inlet.
Use suction pipe one or two sizes larger than the pump suction, with a
reducer at the suction flange. Suction piping should never be of smaller
diameter than the pump suction.
Provide access and service space around and over cooling towers as
indicated, but in no case less than that recommended by the manufacturer.
If the tower consists of more than one cell, totally isolate each cell from
the other cell to facilitate cleaning and maintenance. Provide equalizing
piping between cells with automatic control valve.
For proper installation and operation of Fan Coil Units (FCU), the
following shall be checked and adhered to:
Allow adequate space for the unit and free area or service clearance, refer
to manufacturer’s general unit dimensions and submittal drawings. For
proper servicing and routine maintenance, access to the unit through
removable panels in the ceiling must provided.
Before installing any unit make sure that proper preparation has been
made at each unit location for piping and electrical connections.
The clearance between drain pan and ceiling should be enough for drain
line pitch with a minimum slope of 1:50.
Condensate protection for the chilled water valves and piping must be
provided by installer. A drain pan extension provided by installer should
be located under the valves or else the valves and piping should be
thoroughly insulated.
Units with valve package are equipped with long drain pan which can
carry the condensation from water valves. Insulation of valve package is
not required.
Place the unit to desired angle by adjusting lower nuts up/down, and then
tighten the upper nuts to secure the unit.
Adjust the slope of the drain pan by turning the drain pan suspension
screws up/down. The drain pan should be pitched to provide proper
drainage. Note side to side as well as end to end level. Level the unit by
checking on the unit casing. Do not use the coil or drain pan for leveling
as they are pitched to provide proper drainage.
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Machine connections such as ducts, pipes, electrical, and condensate must
conform to engineering catalogue provided by manufacturer as to sizing,
location, or orientation for proper operation and maintenance of the units.
Electrical isolation switch for each FCU shall be provided nearby the unit
as safety measure during maintenance undertakings.
Exhaust fans shall always be mounted to a flat level, solid and rigid
structure. Particular caution should be exercised when installing fans on
metal buildings. Be sure wall or roofs are capable of supporting the fans.
Roofs not supported correctly will cause vibration that could cause
damage or injury.
Supports for suspended fans must be crossbraced for live load support to
prevent side sway.
All electrical work must be done in accordance with local and/or national
electrical codes as applicable. Installing electrical wiring must be carried-
out by a qualified electrician.
Make sure power is turned off and locked in the OFF position at the
service entrance before installing, wiring or servicing the exhaust fan.
Before wiring the motor, check the supply voltage against the motor
nameplate voltage. High or low voltage can damage the motor and void
the motor warranty.
Before starting the fan, turn the wheel to assure it rotates freely. If needed,
adjust the wheel/ shaft/bearing/motor position as required to achieve
necessary clearances.
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On belt drive units, assure belts are tensioned and aligned properly. Check
all setscrews and keys. Tighten as necessary prior to fan start-up.
In general air handling unit do not require special attention other then
routine cleaning and maintenance work. Following is the recommended
schedule of maintenance, when units operate at normal conditions.
However actual conditions of use/operation will dictate the interval of
checking/replacement of the filters, belts etc.
Weekly:
Semi-Annually:
Annually:
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It is important to check the condition of filters once a week. When the
pressure drop across the filter exceed the maximum pressure drop. Dirty
filters reduces the air flow and hence the capacity. Do not operate the
system without filters. In case the media is synthetic or metallic, they can
be cleaned or washed. However it is recommended to replace synthetic
media once in every year and metallic media once in every two years.
Other filters such as Throw Away Panels, Bag, Absolute, Roll Filters must
be replaced with new cells of identical media and efficiency.
Weekly:
Quarterly:
Semi-Annual:
Annually:
A) Sample compressor oil for oil analysis and to check for acid. Replace
if necessary.
Monthly:
Semi-Annual:
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A) Check that the foundation and hold-down bolts are tight.
B) Check the packing if the pump has been left idle, and replace as
required.
C) Check the shaft alignment and re-align as required.
Annually:
Monthly:
A) Inspect general condition of the unit and check for unusual noise &
vibration.
B) Check air inlet louvers for blockage and clean as necessary.
C) Check and adjust water level in basins.
D) Check operation of make-up valve.
E) Check and adjust bleed rate as needed.
Quarterly:
Annually:
A) Sample oil for oil analysis (gearbox) and to check for acid. Replace if
necessary.
B) Check for alignment and unit finish if need re-furbishing or major
repair.
Monthly:
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C) Check the drain pan to be sure that it is clean and free to carry the
flow of condensate through the drain line.
Annually:
B) Inspect the fan wheel and housing for damage. Rotate the fan wheel
manually ensure that no obstructions are blocking its movement.
C) Inspect the coil fins for excessive dirt or damage. Remove dirt and
straighten fins.
H) Access door seals are to be checked to ensure that the seals are in good
order to maintain air-tightness of the unit.
C) All motors supplied with the exhaust fans carry a one-year warranty
from date of shipment. For repairs within the warranty period, the
motor must be taken to the motor manufacturer’s authorized service
dealer.
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D) A periodic motor check should consist of spinning the motor shaft with
the power off to be sure the motor turns freely and the bearings run
smoothly. The belt on belt driven units should be removed from the
motor sheave.
E) When removing or installing a belt, do not force the belt over the
sheave. Loosen the motor mount so that the belt can be easily slipped
over the sheave.
F) The belt on belt driven units should be removed and carefully checked
for radial cracks, ply separation or irregular wear. A small irregularity
in the contact surface of the belt will result in noisy operation. If any
of these defects are apparent, the belt should be replaced. Check the
sheaves also for chipping, dents or rough surfaces, which could
damage the belt.
G) The correct belt tension is important. If the belt is too tight it will
result in excess bearing pressure on the motor bearings and shaft
pillow block and may also overload the motor. If the belt is too loose it
will result in slippage, which will quickly burn out belts. A belt should
feel “live” when thumped, approximately ¼” belt deflection when
subject to finger pressure (3-5 lb.) at midpoint between sheaves.
2.9.1 Chillers
The chillers are provided with three position selector switch that is,
“HAND, OFF, and AUTO.”
If the selector switch is in the “HAND” mode, manual operation will take
place with the chillers. BMS access will be disabled but the operation of
the chillers can still be monitored by BMS. With the “HAND” mode,
water flow switch will send signal to chillers controller to energize the unit
provided all the safety interlocks are meet (cooling tower, pumps, AHU,
and FCU are operational or energized).
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If the selector switch is in the “OFF” mode, chillers are stop and no chilled
water will be available in the system. This chillers mode will be monitored
via BMS.
If the selector switch is in the “AUTO” mode, the Direct Digital Control
(DDC) control will send signal to the respective motorized valves to open
and when flow switch sensed a flow of water, chillers will be energized
with confirmation from all safety interlocks.
BMS will acknowledge any abnormalities (low, high, fail) on the chillers
operation.
Like the chillers, cooling towers has three position selector switch for its
operation. At normal operation, cooling tower fan and condenser pumps
will be energized first prior to the operation of any chillers since
condenser water flow is interlock with the chillers operation. Water level
on the tower sump shall be check and monitor during operation. Likewise,
the tower fan rotation shall be check prior to operation. Cooling towers
operation shall be control and monitor via BMS.
The operation of chilled and condenser water pumps shall be as per the
demand of chillers and cooling tower units respectively via BMS based
upon a programmed loading demand.
All safety and alarm points (low, high, fail) for pressure and temperature
shall be displayed and monitored via BMS terminal.
Like the chillers, AHU shall have “HAND, OFF, and AUTO” selector
switch for operation and stopping of unit.
Exhaust fans can either be energized manually or through the BMS and
are interlock with the FCU serving the same area. When smoke is detected
by two area smoke detectors installed in the served area or installed in the
main exhaust duct, an alarm will be sent to the fire alarm control panel and
to the BMS to operate the related exhaust fans continuously until the
smoke is cleared while the FCU is shutdown.
EMERGENCY CASES
During emergency cases like fire, an alarm signal from fire alarm control
panel (FACP) will be sent to BMS to shutdown all HVAC related
equipment and accessories. Smoke extract fans will be energized to relieve
the building from heavy smoke.
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