Below is mechanical method statement that is prepared in order to make sure that site installation of all types of Fan Coil Units and Packaged Air Conditioning Units and associated refrigerant pipework is done as per applicable requirements and manufacturer instructions.
Procedure defines the method that will be used to ensure that the FCU & Packaged Air Conditioning Units and associated refrigerant pipework and accessories are installed as an integrated system correctly and in acceptable way and conforms to the contract documents and technical specifications.
This hvac method statement covers the following:
Fan Coil Units FCU (all types)
Package Air Conditioner – split floor
Package Air Conditioner – split ceiling
Refrigerant Pipework
U-PVC Pipework
RESPONSIBLE PERSONNEL
Construction manager, mechanical engineer and site supervisor are responsible for the implementation of this hvac method statement on site.
PRE-INSTALLATION REQUIREMENTS
All materials and documentation relevant to a particular section of works will be checked by the construction department prior to the commencement of work ensuring that these are of the correct type as reviewed by the client and as per applicable specs.
Before commencement any construction works, pre-inspections will be carried out on all materials prior to them leaving the storage area.
Prior to the commencement of any construction activities, areas and access will be inspected to confirm that they are in suitable condition for construction works to commence.
METHOD OF FCU INSTALLATION
All lifting, handling and installation of the plant equipment procedures will conform to the manufacturer’s instructions, ensuring at all times that packaged air conditioning units and FCU’s are not subjected to undue stress.
Check that the Fan Coil Unit to be installed has the correct model and type.
Floor mounted units will be free standing, self supporting assembly, and will be bolted to the “Housekeeping Pad” with anchor bolts ensuring the assembly is horizontal and vertically in alignment, and isolated from the pad using rubber-in-shear isolators with a minimum deflection of 5mm.
Units mounted on suspended slabs with fan motors up to 7.5 kw will be isolated using spring isolators with a minimum static deflection of 20mm.
For the units with a higher fan motor rating, the spring isolators will have a minimum static deflection of 40mm.
All packaged units will have vibration isolator installed internally on all reciprocating equipment.
Locate unit as shown on latest approved shop drawing.
When fixing support it will be ensured that they are of adequate strength to hold the units weight.
Support sizes must be inline with the approved shop drawings.
Position hanger rods and check for alignment with the unit.
Lift and position unit in a safe manner using lifting tackle if required or suitable lifting gear.
Firmly secure unit to the supports and make sure that the base of the fan-coil unit is leveled horizontally.
Make sure that FCU shall be accessible for change of filters and general servicing and maintenance.
METHOD STATEMENT FOR CONDENSING UNIT INSTALLATION
Check and ensure housekeeping pads are properly leveled and are in the correct location as per approved layout drawing.
Securely place and bolt the unit to the house keeping pads ensuring that it is leveled in all directions, and the anti-vibration pads are installed as detailed on approved construction drawings.
Unit surroundings must be well ventilated and there should not be any obstructions to the air flow in or out of the unit.
METHOD FOR COPPER REFRIGERANT PIPEWORK
Minimize pipe lengths and number of bends as recommended by the manufacturer. Bends will be carefully formed so as not to crush the pipe, pipe bender will be used.
Ideally there should not be any joints in the pipework between fan coil unit and condensing unit.
Liquid loops or oil traps will be provided according to the position of the outdoor and indoor units – check carefully the approved drawing for position and dimensions of loops required.
If fan coil is located above outdoor condenser unit the loop will be above ceiling grid and prior to final connection to fan coil.
If fan coil is installed below condensate unit the loop will be directly adjacent to the condensate unit.
FLARING TECHNIQUE FOR CONNECTIONS TO FAN COIL UNIT
Cut the pipe stages by stages, advancing the blade of pipe cutter slowly.
If extra force is used the cut will be deeper and can cause more distortion of the pipe and undesirable rough finish.
Remove with the burr remover ( usually incorporated in the pipe cutter ). This will avoid unevenness of the flare face which could cause refrigerant to leak.
Hold the flaring end down to prevent burrs from dropping inside pipe.
The exact length of pipe protruding from the face of the flare die is determined by the flare tool.
Fix the pipe firmly on the flare die.
Match the centers of both the flare die and flaring punch; and tighten flaring punch fully.
METHOD STATEMENT FOR COMPRESSION COUPLING JOINT
Place compression joint nut over copper tube from the unflared end or alternatively on the tube prior to the commencement of the flaring operation.
When making the final connection of the compression fitting, tighten the nut by hand and using the correct size spanner, fully tighten nut until the fitting firmly grips the tube.
Do not over tighten otherwise distortion of the pipe may occur.
INSTALLATION OF AEROQUIP VALVE TO CONDENSING UNIT
Lubricate male half of the diaphragm and the synthetic rubber seal with refrigerant oil.
Thread coupling halves together by hand to ensure proper mating of threads.
Use proper size wrenches ( on coupling body hex and on union nut ) and tighten until coupling bodies “bottom” or a definite resistance is left.
Using a marker pen, mark a line lengthwise from the coupling union nut to the bulk head, then tighten an additional 1/4 turn: the misalignment of the line will show the amount that the coupling has been tightened.
This final turn is necessary to ensure the formation of a leak proof joint.
INSTALLATION OF CONDENSATE DRAIN PIPES
Factory standard insulated drain pans shall be provided with each fan coil unit.
Piped drain connection to the bottom of the pan via an approved union and a sealed trap to the exterior of the unit housing.
The trap will be configured and sized to maintain a seal under full load, dirty filter and wet coil condition and discharge into a dish connected to the condensate drain line.
Engineer will check trap depth against latest design details.
Condensate discharge will be run to the nearest drain point and shall be visible for inspection and maintenance at final discharge location.
REFRIGERANT PIPEWORK PRESSURE TEST & CRITERIA
- Check flare connections at Fan Coil Unit and Condensing Unit.
- Ensure valves are isolated at the Condensing Unit.
- Connect line from condensing unit (pipework side to Nitrogen and set system pressure to approximately 0.2 KPa.
- Open liquid line access port and purge air from the system using Nitrogen introduced via the suction valve access port.
- After system has settled at the set pressure, isolate the connecting lines to the Nitrogen and other system.
- Fit “ Quick Couplers”: to one of the access port for sampling the pressure with gauges.
- Record the date time and measured pressure of the system.
- Using a foaming liquid leak detector agent check all visible flare connections.
- After a duration of 2 hours check the system pressure and compare the results.
- Raise pressure to 30 kPa.
- Record date, time and system pressure to hold for a period of 10 hours for a successful pressure test no pressure drop is permitted.
- On completion of the pressure test, vent all Nitrogen from the system via the valves access ports.
INSULATION OF CONDENSATE DRAIN PIPE
Condensate drain pipework will be insulated with Nitrile Rubber insulation 19mm thick with a dull matt finish.
This insulation is tubular and will be threaded over the pipework in a continuous length.
When small areas at fitting traps or end of runs need to be installed, the tubular insulation will be cut into the appropriate lengths ready for installation.
These sections will be cut longitudinally, then opened out and fitted into the appropriate gap.
Were joins are formed they will neatly butt against each other, the resulting butt joint will be sealed with the approved self adhesive insulation tape.
Refrigerant Pipework will be insulated with Nitrle Rubber insulation 32mm thick for diameters below 40mm and 50mm thick for diameters 40mm and above.
REFERENCE DOCUMENTS
- FCU Installation Tracking Check List
- Approved Shop drawing
- Inspection and Testing Plan
- Manufacturer’s Instructions for the Packaged Air Conditioning Unit / Fan Coil Units