Electrical underground pull boxes are used in various industries for pulling, splicing, and storing cables. They offer a reliable, safe, and budget-friendly housing for system equipment. Besides, they provide easy access to underground electric utilities, water lines, telephone power, data & communications cables, etc. They are the more advanced and efficient alternatives to traditional concrete service boxes.
Electrical underground pull boxes are known by many names. The terms handhole, junction box, underground enclosure, underground utility box, splice box, and access box are interchangeably used to indicate them.
A wide array of boxes is available in different sizes, specifications, and materials that are used in transportation, construction, C & I, electrical utility, CATV, DOT, water utility, and telecommunication industries. They ensure the safe housing and future easy access to stored wiring and electric equipment.
Installation of Electrical Underground Pull Boxes
You have to follow your local utility guidelines for installing an underground pull box. However, there are still some standard principles and rules that have to be applied during the installation. Let’s take a look:
You have to ensure a firm base for the underground electrical pull box. A layer of minimum 6 inches of aggregate under the box will give it the proper support as well as help in drainage.
You have to dig an area approximately 12 to 18 inches bigger than the box’s base and at least 6 inches deeper than its height. The extra 6-inch space will be used for putting the aggregate.
You have to prepare the base properly to keep the box firmly in its place. Besides, a solid foundation is required for the bottom flange to rest on.
Use a mix of stone dust, soil, and gravel to solidify a 6 inches area on the excavated hole. After you have placed the box and level it, put 3 inches of soil on the flange to ensure that the box will stay in place.
You can use the materials that have been dug up during the excavation of hole for backfilling the exterior wall. Backfill in at least 6 inches increments and pack it by tamping.
Don’t use large concrete pieces, rocks, stones, or frozen chunks for backfilling and avoid forceful tamping by using mechanical equipment. Never use sand for backfilling because it creates enormous pressure on the side wall by yielding zero frictional resistance to movement.
The entire process of installing electrical underground pull boxes needs to be dealt with caution and care. Keep in mind the following points during the installation:
- Handle all the drill works and any modifications to the box with care
- The flange works as the support hoop, so don’t ever cut it
- Check if the cover is bolted in place during the backfilling
- Use concrete collar around the box if it is installed in an area that is exposed to heavy equipment or prone to wash away of the soil