Installation Requirements for HVAC Ducts
Pre Requirements before the start of installation of air conditioning ducts which are already fabricated either on the site workshop or from outside the project premises and delivered to the site for installation after duct fabrication.
Fabricated Ducts delivered from duct workshop to be stored in dry-clean and safe area to be selected on site. All materials and documentation relevant to a particular section of works will be checked by the construction manager prior to the commencement of work ensuring that these are of the correct type as reviewed by the client.
Before commencement any construction works, pre-inspections will be carried out on all materials prior to them leaving the storage area i.e. quantity, physical damage and brand/make etc.
Prior to the commencement of any construction works, areas and access will be inspected to confirm that they are in a suitable condition for construction works to commence, scaffolding of suitable height will be arranged.
Works shall not proceed until an approved shop drawing or detail is issued. Safe Access to work areas shall be provided and shall be approved by the competent safety person prior to commencement of works. Materials shall be moved to the work area in safe manner and shall not block access /egress from/to the site.
Suitable Mechanical aids shall be used where heavy loads are to be moved or lifted in to position, such equipment shall be planned for in advance of works. Where high risk works are involved then a safety clearance must be obtained from safety department.
- Supervisor will instruct tradesmen regarding the execution of the works and will distribute all necessary approved construction drawings of the latest revision.
- The supervisor will also check that tools and equipment’s and scaffolding available are in compliance with the contractor requirements/safety standards and as per necessity.
- Ensure horizontal ductwork is adequately supported at equal distances in accordance with construction drawings with all brackets fixed to the vertical face of ribbed beams of the structure.
- Care will be taken during setting out, that ductwork runs between ceiling module lines so as to maintain maximum flexibility for any future relocation of lighting fixtures or other services.
- Ductwork supports unless otherwise indicated will be installed to provide a minimum space of 15mm between finished covering and adjacent work, and 100mm clearance from suspended ceiling.
- Supports or hangers will be placed within 300mm of any 45° – 90° bend.
- Screwed drop rods will have thread adjustment in either direction available after levelling of ductwork and associated plenum boxes.
- Ducts will be supported within 300mm of mating flanges or joints.
- As indicated on relevant approved construction drawings where more than one duct can be supported on one hanger – the size of the hanger will be assessed on the sum of the maximum widths.
- Ductwork passing through non fire rated walls and floors will be adequately supported on either side.Supervisor to ensure that there are no dents, distortion or buckling of ducting during installation being aware that damaged sheet metal work will be rejected.
- All locknuts should be tightened correctly andall open ends’ should be cleaned from debris and then covered with suitable material to prevent any ingress of debris, vermin, or moisture.
- Supports are to be fixed at correct levels checking the bracket material is compatible with the installation and the correct method used for thermal insulation.
- Ducting to be installed allowing sufficient space for expansion/contraction and thermal insulation.
- Fixing of flanges to ductwork will be by the approved details and in compliance with the specification requirements.Continuously check horizontal and vertical alignment of ductwork and compliance with contractor’s drawings and specification requirements by using spirit level plumb or other suitable instrument. Clean both flange faces to be joined. Add gasket jointing material to flanges to be mated. Using only undamaged rust free bolts nuts and washers join mating flanges together and tighten bolts. Clean any excess jointing material from flanges.
- In line equipment is to be independently supported from main structure and not block work walls or sub-structure.
- Silencers, fire dampers, balancing dampers & other plant items will be installed as per shop drawings, and will be supported adequately.
- Supervisor to check before end of work every day that: The correct type of supports are installed, supports are adequately supporting the ductwork and associated plant equipment.
- 25mm diameter air volume test holes with tight fitting plastic plugs shall be located as required for commissioning purposes.
- Ensure terminal equipment is installed as specified.
After the HVAC Duct Installation
Supervisor to ensure that all completed installations look neat and tidy, and that there is adequate spacing between ductwork and in line equipment allowing access for operation and ease of maintenance, to approved drawings and manufacture’s recommendations.
The supervisor in charge shall continuously monitor the activities to ensure that all components indicated on the approved shop drawings have been installed and that the installation is in accordance with the contract requirements and specifications.
Complete method statement for installation, insulation and pressure testing can be downloaded from this link.