choosing Refrigerant Piping Selection Tips DETAILED TECHNICAL SPECIFICATION

الحمد لله والصلاة والسلام على رسول الله وعلى آله وصحبه أجمعين 

choosing Refrigerant Piping Selection Tips 
DETAILED TECHNICAL SPECIFICATION

a) Refrigerant piping assembled must consist of copper tubing 
to ASTM specifications B.88, Type “K” hard drawn and soldered joints
Fittings must be of wrought copper or fine cast brass. Where required
for gauges, etc., tubing not larger than 10mm. Diameter may be of 
type “K” soft (annealed) with flared tube or double ferrule compression
fittings suitable for high pressure. Flux and solder as recommended by 
the manufacturers of tubing and fittings only must be used during installation

b) Refrigerant piping must be installed so as to ensure continuous and 
automatic return of oil to the compressor. Gauges and meters etc
supported directly on piping must be properly leveled

c) Refrigerant stop valves must be back seating, key operated
seal cap type. Valves, which are to be in constant use, must
have hand wheels and must be packless type
Valves connected in copper tubing must have solder type ends or 
flanged end and soldered flanged adapters

d) Accessories for field-assembled system like oil separators 
liquid receivers, heat exchangers, expansion valves, etc 
must be installed as per manufacturer’s recommendations and specifications

e) Replaceable core type filter drier with by pass valves and
liquid sight glass must be provided

f) Pump down system must be provided for each unit

Pressure Tests

After installation is completed, but before piping is furred in or 
before insulation is applied, all piping and equipment must be 
tested for leaks using Nitrogen or an approved gas

Vacuum Test

Before charging the system with the refrigerant, it must be
dehydrated thoroughly, using a high efficiency vacuum pump
and vacuum indicator. Dehydrating operation should continue
until a reading of 35 FWB at a pressure of 5.2mm HG absolute is reached

Return Air Plenum

Return air plenum must be an integral part of the unit, factory assembled
Plenum must be suitable for accommodating 50 mm. thick metallic cleanable
filters with a face velocity not exceeding 1.8 m/sec
However, equal and approved field installed filter plenums are also acceptable

Control Wiring & Protection Devices 

The thermostat control voltage must be 24 volts
The A/C units being offered must feature the following minimum
requirements of safety interlocking and protective devices 

Safety electrical and mechanical interlocking of evaporator fan motor 
with compressor / heater operation and interlocking through an airflow switch
wherever duct heaters are provided

Where multiple compressors are incorporated in the units their 
operation must be in sequence in accordance with return air temperature

Manually reset and adjustable oil pressure differential cutout
of 90-sec/120 sec. trip time rating for compressors of 25 HP and above

Manually reset and adjustable high pressure and adjustable
automatic low-pressure cutout for compressor protection 

Time guard circuit for preventing compressor rapid recycling
preferably of adjustable range from 5 minutes to 15 minutes

Time delay relay for sequence starting of multiple
compressors system of minimum 15 sec. delay rating

Separate single phasing preventor suitable for three phase 
415 volts, 50 Hz. power supply to prevent the whole unit from
single phasing phase shift and under voltage with a response
time rating of maximum 2.0 sec

Inherent thermal protection for compressor motor winding 
three phase evaporator fan and condenser fan, motor windings

Inherent thermal protection or manually reset thermal or magnetic overloads 
for single-phase condenser and evaporator fan motors

External thermal overload with manual reset or MCCB of
suitable rating for all three phase motors in addition to (h) above

The unit must be controlled by a duct thermostat housed in a
suitable perforated transparent casing with a lock. Control
voltage of the circuit to which thermostat is connected must be 24 V

The control panel must be IP 54 at least 

Return Air and Fresh Air Filters

1) Return air filters must be permanent and washable type made of aluminium 
or G.I. sheet designed for heavy duty and must be sized for maximum 
air velocity of 350 ft. per minute with initial pressure drop of not more 
than 0.25 inch W.G. at the rated air flow. Filter media must consist of 
cripped G.I. or aluminium arranged to give maximum area for airflow
2) Return air filters must be enclosed in a separate filter frame
integral unit.
3) Fresh air filters must be of the same specification as return
air filters.
4) Thickness of return air filters must be 2″ and that of fresh air filters must be of 4″

Drain-pipe sizes must be minimum 19-mm. diameter and
the material must be GI. The drainpipe must be
connected to the drain point of the unit with transparent
plastic flexible hose and jubilee clips

Thermostat must be provided for each unit

All mountings, brackets, bolts, fixtures, etc. for installing
the condensing unit and fan coil unit must be provided

All mini-split A/C units must be provided with proper earthing 

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