• • • CASE STUDY • • •
Delivering the largest prefabricated electrical installation in Europe
Pete Willsher, managing director at RMS, explains how an offsite manufacturing solution developed with LMOB electrical contractors helped meet demanding time deadlines for the £885 million 40 Leadenhall development in London for the electrical, telecoms and fire safety installation. The project claims to be the largest offsite manufactured electrical and building services solution in Europe to date
4
0 Leadenhall is a 900,000sq ft office development featuring retail and leisure facilities in the City of London. It is in EC3, which is the historic and dynamic insurance district, and will make a confident statement within London’s famous skyline.
The building itself consists of several stepped blocks that includes two towers, one of which is 34 storeys tall and the other 14 storeys high. The development aims to meet the BREEAM NC 2011 “Excellent” standard with the proposed sustainability measures allowing the Building Emissions Rate to be 40% below Part L2A of the 2010 Building regulations.
The challenge for the electrical and building
services was to find a solution that contractors could install incrementally one floor at a time while sticking to a strict timetable to keep the project on track.
Rising challenge
Due to the scale of the project, the electrical contractor LMOB needed to install seven main risers, three in one tower and four in the other. Four of these were for electrical services, three for telecommunications and one as a fire rated riser for alarms, emergency lighting and other safety critical equipment. They also needed a cable management solution to run the cabling to services on each floor.
LMOB contacted RMS with a proposed design for the main risers. These would be modular units that interconnect between each floor and are complex structures that need to accommodate the huge amount of services, equipment and cabling needed.
Due to the complexity of constructing such units on site, it was decided that an offsite solution delivered to site incrementally to match the build schedule was the best option.
Offsite solution
Offsite manufacturing enables manufacturers to control the build of a system and ensure adherence to strict factory-controlled quality assurance. It also removes a complex task from the construction site to reduce labour and improve health and safety.
In common with more general manufacturing solutions, it also allowed RMS to prototype a riser module for testing and inspection before committing to manufacturing. It is one thing to have a design concept for a solution but for large complex projects such as this it really pays to prove that the concept will work in practice. After some tweaks to this prototype “test module” all those involved in the decision were confident that the proposed solution would work on site.
RMS produced this test module in just two days ready for inspection before an initial visit to the factory. Rapid prototyping and design reiteration is a common process in mainstream manufacturing and there is no reason why it can’t be applied to offsite construction. After all it is better to test a concept, rework it and have it signed off as a system instead of having to make alterations after delivery to a busy construction site.
For the main installation RMS manufactured 460 modular riser units that the contractors installed one unit at a time. Many of these risers had services, such as electrical distribution boards installed within them. To achieve this, contractors from LMOB worked on site at the RMS facility in close collaboration with the frame manufacturers. This ensured that each prefabricated riser module with preinstalled services was quality tested and certified before delivery.
RMS scheduled deliveries with LMOB so that the riser unit modules for each floor, plus standard cable tray, trunking and other cable management products all arrived one week in advance, as a complete package. In total 460 riser units plus 10,000 metres of cable trunking and tray were delivered for the project.
Each riser module connects to the module on the floor above and below it using adjustable couplers, also designed and manufactured by RMS. This catered for height variations since the concrete floors between levels have different thicknesses depending on how high each floor is in the building, with lower storeys having thicker floors.
Time saving solution Talking to Richard Pendleton, operations director at LMOB, he estimates that the electrical installation time for each floor was cut down from an expected three weeks to just three days. When working on large projects like this, the need to co- ordinate different trades means any time savings are a major factor in keeping schedules on track. Working closely with LMOB also prescribed a major logistical exercise to ensure that the right systems and standard products were all delivered to a central London site on schedule. The modular riser variant would be dependent on which floor they were for, so for example, the electrical risers for every fourth floor would contain electrical distribution boards which the contractors on site had to connect and test.
When people talk about offsite construction,
they often envisage complete pods that are simply delivered and bolted together. Often however a pre- fabricated, manufactured solution simply removes
34 ELECTRICAL ENGINEERING • JUNE 2023
electricalengineeringmagazine.co.uk
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