Under almost every parking lot, along every sidewalk and roadside verge in the UAE is a small box of concrete with a slight gap in it and one that no one really notices until the technicians have to pull a new cable through and can’t find one. That box is more than just working, it is working harder than it looks. Let’s go over the steps to specifying and ordering the proper precast concrete pull box.
The Truth About and the Myth of a “Pull Box”
A pull box (also known as a handhole) is a specific precast underground box which provides access to underground electrical or telecommunications cable for the technician to pull without having to dig the ground each time. Similar to a manhole, but different. Pull boxes are access points for pulling and feeding conductors, and are not permanently filled with wiring like a manhole may have for continuously active splicing or junction equipment.
For this reason, precast concrete versions are the most prevalent. They help avoid damage to electrical and telecommunications infrastructure, prevent tampering, and structurally support the box due to proper manufacturing and curing processes, which are important considerations when the box is buried and backfilled and is essentially out of sight for the entire service life of the box.
This Factor Varies According to the Need of the Application
Pull boxes are not all the same size, they grow with the volume of cable, splice requirements and access. Smaller boxes are typically about 13 x 24 inches and have a corresponding opening and approximately 12-inch height, which are ideal for lighter cable routing applications, whereas larger boxes take a quantum leap for heavier electrical and multi-conduit telecom applications.
Typically, manufacturers supply sizes and shapes with or without knock-outs to provide the engineer flexibility to match the box to the conduit configuration on a given project. When ordering, be sure to check with your electrical or telecom consultant on the actual cable count and number of splices your project will require; otherwise, you’ll have trouble maintaining a cable pull box the first time a technician is trying to do work inside of it.
Load Rating: Not All Boxes Are Alike
This is one of the most crucial differences to make and one of the easiest to miss. Pull boxes are available in traffic-rated and non-traffic-rated versions, and using the wrong one is a real safety and durability concern. There are product families that are specifically designed for loading in traffic or road surfaces—and families that are explicitly labeled as non-traffic rated, for pedestrian areas, landscaped verges or any place where there is no vehicle loading.
Please specify the load rating for each pull box when placing an order directly with the supplier, and verify the load rating against the actual site and not the general type of project. A pull box that is under a parking aisle or access road should always be the traffic-rated version. There are no exceptions for convenience or stock availability.
Duct Access and Knockouts Are as Important as the Box
The pull box must be installed so that cable can be easily inserted and removed, which is achieved by duct access knockouts (duct bank windows) installed so that the conduit runs to and from the duct align. Where the project requires a more finished, sealed connection point, some manufacturers will provide duct terminators as an alternative to duct knockouts.
Inquire from the supplier about the number of knockouts or duct terminations in your box and make sure that the locations are correct for your duct layout. A pull box with knockouts in the wrong location means that the installer must core through solid precast concrete during installation, which defeats much of the purpose of using a factory-made product in the first place.
Cover and Frame Design
Much more is done by the visible part of a pull box than it appears to do. Many precast pull boxes include a cast iron frame and cover as standard, providing a tough, load-specific closure that keeps the enclosure beneath secure from debris, water and unauthorized access.
Covers are also sometimes needed for certain applications where there are specific safety and identification requirements, such as traffic signal wiring, and have an embossed marking for their function in addition to pull slots sized to the appropriate specification and a skid-resistant surface. If you are using traffic signal, streetlight or public infrastructure cabling, be sure to verify with your supplier if you require this type of application-specific marking on your covers.
Hardware and Security Details
A pull box should be easy for authorized technicians to open, but difficult for casual users to access. The materials used to secure the cover—stainless steel or brass—are chosen for their resistance to corrosion over decades of underground use, which is important in the UAE’s combination of heat, humidity and, in some places, coastal salt air, where these components are expected to last for many years.
Do enquire of your supplier what material they use normally for their hardware. After only a few years of service, a pull box with rusted fasteners can become difficult to open safely, rendering the whole idea of a pull box for maintenance access useless.
Reliable Watertightness Is Indeed a Design Factor
The combination of standing water and buried electrical and telecom infrastructure is not a good one, and pull boxes need to get this right. Boxes can be made watertight by precast concrete construction and this quality improves through continued curing of the concrete in the ground, compared to other materials that may deteriorate when continuously exposed to moisture.
Inquire with your supplier what watertight performance they achieve with their standard pull boxes and whether there are any special measures recommended for projects located in high water table areas or locations where flooding may occur, which is a realistic consideration depending on the location within the UAE.
There Are Options to Customize for Non-Standard Projects
There are lots of common applications available in standard catalogs, but many projects require a custom approach. Custom cutouts with conduit positioned exactly where it needs to go are available from capable manufacturers and some even have locks and lids on the conduit to provide additional protection over the cover and hardware on sites that require more protection than standard products provide.
If your project’s cable configuration is unusual, has specific security requirements or uses a duct layout not covered by a standard product, ask your supplier if they can design a custom box instead of modifying your project around an existing one.
The Application of Alternative Materials – and Polymer Concrete’s Place in Them
There are other concrete products besides standard precast concrete. Polymer concrete can be formulated using a polymer resin system and selectively graded aggregates and reinforced with fiberglass to provide an alternative that is lighter in weight, offers excellent corrosion resistance and, more importantly, is non-conductive, eliminating the need to ground the box or cover.
This may be important for particular applications where weight or conductivity is a genuine concern. Traditional precast concrete is still the preferred and proven solution for most standard electrical and telecom routing requirements in UAE infrastructure projects, particularly with regard to traffic loading and long-term durability under high temperatures.
Know the Signs of a Red Flag Precast Concrete Pull Boxes
There are a few warning signs that are repeatedly encountered with weaker pull box suppliers. Be aware of a lack of clear load rating per box, vague responses regarding duct knockout positioning, standard hardware with no mention of corrosion resistance details and no discussion of custom sizing for non-standard duct layouts.
None of these should be a deal breaker for a supplier. Where two or three exist, however, it is worthwhile to pause before ordering boxes that will be buried and relied upon for years of maintenance access.
The Bottom Line on Precast Concrete Pull Boxes
The selection of the proper precast concrete pull box is not simply a matter of buying the box that is the closest match in size, but of specifying the correct size, load rating, knockout position and hardware for the actual cable routing and site traffic. If these details are incorrect, technicians end up battling an access point that was not originally intended for their site. If it’s done right, the box does exactly what it’s supposed to do: sit quietly in the ground until someone needs to open it.
