Low-voltage systems, such as network cabling, WiFi, phones, security cameras, access control, AV and building automation, are often designed late and squeezed in at the end of a project. That leads to missing pathways, undersized telecom rooms and change orders. The fix is to bring low-voltage design in early, coordinate it with the other trades on the drawings, and plan its place in the construction schedule.
What counts as low voltage
On most projects, the low-voltage scope includes some or all of:
- Structured cabling for data and voice
- WiFi and in-building cellular systems
- Security cameras, access control and intrusion alarms
- Audio-visual systems, paging and digital signage
- Building automation and metering networks
- Nurse call, intercom and other specialty systems
Fire alarm is usually a separate scope with its own standards, designers and inspection requirements. Even so, its pathways and spaces need to be coordinated with everything else.
Start in design, not in the field
The decisions that are cheap during design and expensive later include:
- Telecom room locations and sizes, within cable distance of every outlet
- Dedicated power, cooling and bonding for telecom rooms
- Vertical sleeves and riser pathways between floors
- Cable tray routes and ceiling space reserved for them
- Conduit and back boxes in walls, floors and hard ceilings
- Floor boxes for boardrooms and open areas
- Mounting locations and power for access points, cameras and displays
- Entrance conduits for carrier services and between buildings
Telecom room planning is covered in telecom rooms: the IDF and MDF. A WiFi design early in the project also tells you where access point cables need to go before ceilings close.
Coordinating with other trades
Ceiling spaces are crowded. Ductwork, sprinkler piping, electrical conduit, lighting and cable tray all compete for the same room. Coordination points include:
- Mechanical and plumbing: keep cable trays and telecom rooms clear of water lines, and avoid routing cable over hot equipment
- Electrical: maintain separation between data cabling and power wiring, fluorescent and LED drivers, motors and transformers; confirm circuits for telecom rooms and PoE loads
- Architectural: ceiling types and access, millwork for AV, and wall construction for back boxes
- Fire protection: firestopping of every penetration through fire-rated assemblies using listed systems
- Structural: supports for heavy equipment, racks and displays, and coring through slabs
Before cutting or coring slabs, existing reinforcing and embedded services need to be located. See cutting and coring concrete safely.
A coordination drawing, or a shared building model on larger projects, is the place to resolve these conflicts. Low-voltage trays and conduit should appear on it alongside every other trade, rather than being left to find space in the field after everything else is installed.
Sequencing on site
Low-voltage work happens in phases, and each phase has its window:
- Rough-in: sleeves, conduit, back boxes and floor boxes, installed with the electrical rough-in before walls close
- Pathways: cable tray and J-hooks installed once mechanical and sprinkler mains are in
- Cable pulling: after walls are up and the building is reasonably dry and secure, before ceiling tiles go in
- Termination and testing: once telecom rooms are clean and lockable, with power available
- Devices: access points, cameras and displays installed after painting and ceiling tiles, to avoid damage and dust
- Commissioning and handover: testing, configuration, documentation and training
Protect cable from the other trades. Cables pulled too early get stepped on, painted, sprayed with fireproofing or crushed by lifts. Telecom rooms used as storage get dusty and damaged. Agree on protection and sequencing in the schedule rather than finding damage at testing.
Installation practices to require
- Cable supported by its own hangers or tray, not lying on ceiling tiles or tied to sprinkler pipes, ductwork or the ceiling grid wires
- Bend radius and pulling tension within the manufacturer's limits
- Correct fire rating for each space; see structured cabling standards
- Firestopping restored after every penetration and every later change
- Labelling and records that follow a scheme agreed at design
- Certification testing of every link before acceptance
How ehZee can help
Our approach starts by asking why the building needs each system, which is the conversation that belongs at the design stage. Through our structured cabling design and build service we can design pathways and rooms, coordinate with the project team, install, and verify with testing and documentation.
Common questions
Who should own the low-voltage design?
Ideally a designer engaged early, working with the architect and electrical engineer. When low-voltage is left entirely to the contractor at the end, pathways and rooms are usually already fixed and inadequate.
Can we add cabling after the ceiling is in?
Yes, with lay-in ceilings, but it is slower and messier. Hard ceilings and finished walls make late additions expensive. Pulling spare cables or empty conduit during construction is cheap insurance.