FMS Articles
As seen in 
Tips abound on managing electro-magnetic interference
by Jon Munderloh
From Buildings magazine, March 1999, Vol. 93, no. 3
As the complexity of technology in commercial buildings increases, interference problems caused by Electric and Magnetic Fields (EMF) are increasing in frequency and severity.
Most electrical and wiring problems are best solved before they become problems. That is certainly the case with EMF. What is unusual in the case presented below is that the problem was anticipated at all. Most buildings encounter the problem long after the most efficient options are no longer available.
In this case study, the management company for an older, 20-story downtown Los Angeles commercial office building had developed a unique strategy to attract new tenants to the aging property by targeting large telecommunications service providers. The building was ideally sited to support what the building management and ownership correctly believed would be an increasing demand for telecommunications services.
As part of a building upgrade, the building ownership planned to substantially increase the power quality and capacity of the facility's infrastructure, both to support the new tenants telecommunications switching equipment and to provide for future growth. The existing utility electric transformer and the building's main electrical distribution equipment were located in the basement parking area of the building. Space and access restrictions precluded installation in the existing basement area. Subsequently, a 2,500-square-foot, street-level space was selected to house a new utility transformer and distribution equipment.
The project's electrical engineer immediately expressed concern that EMF from the new electrical equipment might cause interference with tenant computer equipment in adjacent spaces. One tenant, a large law firm located on the second floor of the building immediately above the planned ground floor electrical facility, was also concerned about possible health risks to employees. Although science has not proven that a risk exists from exposure to EMFs, the building owner was advised that any increase in magnetic field levels, after installation of the new electrical facility, would be viewed with the greatest concern to tenants.
Measurements of several similar electrical installations, combined with computer projections confirmed that substantial levels - in the tens of milligauss (mG) - of magnetic fields would exist in tenant areas adjacent to the new facility, including the second-floor law offices. Ambient or background magnetic field levels in commercial buildings typically range from 0.5 to three mG.
To ensure that elevated magnetic fields would not interfere with equipment in these areas, professionals developed and implemented EMF mitigation measures during the design and construction of the new electrical facility. Although the total mitigation plan increased the cost of the utility upgrade slightly, it was a small fraction of the cost - not counting the tenant dislocations - that would have been required to correct the problem after installation was complete.
Much of the EMF mitigation plan was in the form of low-cost engineering modifications. For example:
- Substantial field reductions were achieved by moving a high-current bus duct that connects the utility transformer to the building distribution equipment, from the ceiling to the floor.
- Special magnetic field shielding scheme was incorporated in the construction sequence.
- Magnetic field shielding material was installed beneath the large utility transformer, on the adjacent walls and ceiling and in the electrical distribution room prior to the placement of the electrical cabinets.
Measurements taken in the adjacent tenant areas and the second-floor law offices after the new electrical facilities were energized confirmed that the mitigation measures had successfully reduced magnetic fields coming from the electrical equipment. Magnetic field levels in the tenant areas and law offices ranged from 0.1 to three mG - a level at or below the comparable levels prior to the upgrade.
The mitigation plan at this stage was comparatively inexpensive. The results were accurately predicted and the project schedule was not impaired.
Jon Munderloh (Jon.Munderloh@FMS-Corp.com) is a Senior Consultant with Field Management Services Corporation in Los Angeles.
EMF Basics
E.L.F., or Power Frequency, magnetic fields are the natural consequence of the use and distribution of electricity. The strength and area of magnetic fields emitted is proportional to the amount of current being used. Consequently, all commercial buildings have areas with elevated fields. These areas are caused by high current-carrying devices (transformers, electric panels) common to all buildings. Wiring errors, as well, can lead to elevated magnetic field levels. Fortunately, in most cases, they are avoidable.
Tips To Spot a Potential Problem
It is very common for magnetic field interference problems to emerge following a building remodel or upgrade, as follows:
- Computer monitors may begin to display jitter, color distortion, or other signs of instability. Other sensitive equipment may be affected as well, including computers, peripherals, data networks and certain medical devices.
- A magnetic field survey of the area should be conducted prior to construction in previously unoccupied areas, now designated as prime office space with computers. Pay particular attention to areas near electrical equipment, including transformers, switch gear or electric service panels.
- Good planning and awareness can minimize the costs of a magnetic field problem. At the building design stage, avoidance costs are minimal, at the outset of a renovation, the costs are greater. After all the trades have left the site, the remediation costs are often substantial.
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