Busbars, like all service penetrations, must be suitably firestopped to ensure effective compartmentation and building safety during a fire.
Nevertheless, firestopping isn’t always linear, especially when it comes to systems like busbars that vary in design, material, and application – all aspects that need careful consideration when choosing the most relevant standard installation details.
What are busbars?
Commonly made from copper or aluminium, busbars distribute and conduct electricity within electrical systems, which has proved to be a more efficient way of carrying larger currents than normal cabling systems. 
You’ll find busbars in buildings like universities, hospitals, and data centres, and may hear them referred to as electrical junctions, bus ducts, conductors, power rails, and bus bar trunking systems.
Why busbars create a firestopping challenge
Different types of busbars
Testing on this type of system will cover other busbars of the “same individual design”, as per BS EN 1366-3, Annex D, Section D.3.6.
However, some busbars from different manufacturers may be classed as the same design, but you may be using a “type” that hasn’t been tested. That is why it is crucial to ensure the selected busbar has a tested fire stopping solution.
Further to this, some power rails may also have cast resin – standard busbar passive fire protection would not cover this type, so specific fire testing would be required.
Busbar material, orientation, size, and weight
Because copper and aluminium react to fire differently, fire testing on one type would not cover the other. This is because aluminium has a lower melting point than copper.
BS EN 1366-3, Annex D, Section D.3.6 does have a field of application that allows certain metal testing to cover certain types; however, this field of application would not allow copper to cover aluminium or vice versa.
Orientation matters too! Busbars can be installed horizontally or vertically through walls, so both orientations must be fire tested.
Moreover, Annex D allows test evidence to cover busbars of the same size as well as smaller busbars. Manufacturers, like ourselves, strive to fire test larger busbars to maximise the scope of application. However, these units are typically heavier, which, as a result, may make physical installation more challenging on site.
Even with a tested fire stopping detail, extra consideration needs to be given by project design teams regarding the space around these systems, and how they will be supported to ensure the application installed is practical for all trades involved.
MEP awareness
MEP designers must know which solution will be used to select the correct busbar. In practice, larger busbars are often chosen over smaller ones to account for how the sealing system may affect performance in everyday use.
How busbars are firestopped using tested systems
Importance of maintaining compartmentation
Fire compartmentation is a critical part of any building’s passive fire protection strategy – “the unsung hero”.
When systems are installed correctly, they prevent fire and smoke from travelling through the building by containing it to its area of origin.
This thereby provides time for residents to safely evacuate if they can, and for the fire and rescue service to arrive, tackle the fire, and rescue trapped residents.
Compartmentation is achieved by dividing the building into areas of manageable risk through fire-rated walls and floors. Every opening that penetrates the compartment line, therefore, must be fire stopped to reinstate the required fire rating.
However, effective fire compartmentation does rely on the correct, tested penetration seals being installed as fire tested.
Quelfire’s firestopping tested solutions for busbars
We have conducted a range of fire tests, using buss bars supplied by EAE Electric through walls and floors.
Flexible and Rigid Walls:
- QB-FW100-D-35
Rigid Walls:
- QB-RW100-D-35
- QB-RW100-P-35
Euroclad Firemaster Walls:
- QB-WW100-D-35A
- QB-WW150-D-35A
Paroc Panels System AST F+ Walls:
- QB-WW100-D-35B
- QB-WW150-D-35B
Paroc Panels System AST F Walls:
- QB-WW150-D-35C
- QB-WW150-D-35D
Paroc Panels System AST L Walls:
- QB-WW150-D-35E
Solid Concrete Floors:
- QF2-CF150-35
Profile Deck Floors:
-
QF2-PD45-35
Hollow Core Floors:
- QF2-HC150-35
We have also tested busbars for under raised access floors; the busbar tested was an Electrak Powertrack System.
For raised access floors, the following firestopping details are used in conjunction:
- QB-RF00-D-00
- QB-FW100-D-36
View the solutions above in our Tested Detail Library.
Busbar firestopping design and specification considerations
Early-stage coordination
A key consideration is ensuring that all those involved in the design, specification, and installation management of fire stop systems are engaged at the design stage.
The sooner everyone gets around the table to discuss important deliverables and find solutions to upcoming challenges, the smoother the project will run. 
And that’s not to say there won’t be any challenges ahead, but early engagement does help to ensure that tested details are applied, coordination is achieved across all trades, and costly rework is avoided.
This level of collaboration outlines a thorough design vital to all build projects, especially those undergoing the Gateway process. Essentially, it’s about following what was agreed upon, with the end goal of protecting people and property.
Tested system selection
Tested systems must be designed into a building from the beginning – and the Gateway regime is now making sure this is properly checked as part of its role in improving building safety. Though we believe this should apply to all buildings, not just higher-risk buildings (HRBs).
It’s the only way to truly know that, in a fire scenario, the fire stopping products installed will perform as intended and that compartmentation can be relied on.
However, to determine the most suitable details, many factors will come into play, such as the size of the service, the details of the substrate, and the required fire rating, for example.
That is why we recommend reaching out to the relevant manufacturer if you need support, as this collaboration will help avoid any hidden costs and delays, and ensure the project is being designed around those critical standard installation details.
Frequently asked questions
Do busbars require specialist firestopping systems?
Yes, any service that penetrates a fire-rated wall or floor must be effectively sealed to retain the required fire resistance, including bus bar trunking systems. Always reach out to a manufacturer of tested firestopping solutions for support on systems that match your application. Early engagement is key here!
What happens if busbars are not firestopped correctly?
Like all service penetrations, if busbars are not correctly firestopped in line with test evidence and guidance, in the event of a fire, the compartmentation will fail, and the fire will spread through the building.
What are the different types of busbars?
Electrical junctions come in several shapes, including rectangular, tubular, round, and flexible. 
As mentioned previously, they are made from one of two materials: copper or aluminium. Copper is preferred for its high conductivity and is typically more durable, whereas aluminium is lighter and more cost-effective.
Who is responsible for firestopping around busbars?
Ultimately, the fire stop contractor must ensure the bus duct fire stopping matches test evidence and manufacturer guidance.
However, other parties do share that responsibility; for example, the architect/designer must make sure the correct, tested solutions are specified for the fire stop contractor to install, while the main contractor must ensure that fire stopping works are compliant.
At Quelfire, we often talk about the fire stopping element of construction being collaborative, yet needing a high level of competency. It’s specialist work, requiring the correct Skills, Knowledge, Experience, and Behaviours (SKEB).
What fire rating should busbar firestopping achieve?
The project’s fire strategy will define the required fire resistance of fire-separating elements, typically shown as an EI rating – E for integrity and I for insulation. The selected passive fire protection system must be capable of reinstating the fire-separating element to this required fire rating.
Please don’t hesitate to reach out to us if you have any questions about firestopping busbars. We're happy to help!
