Before electricians install electrical boxes in or through assembly, they must use only methods, materials, and components that are approved to maintain the rating of the wall. The most common fire wall assemblies for residential and commercial installations are 1 or 2 hour fire-rated walls.
In construction, a fire-resistive wall is meant to limit the amount of heat rise from one side of a wall to the other side. Choosing the right electrical box to maintain the integrity of a fire resistance-rated wall assembly is first based on the rating of the gypsum board and framing (fire-resistive wall assembly). Other factors include the size and spacing of the electrical boxes along with the gypsum panel fasteners.
Fire-Resistive Wall Ratings
Before choosing electrical outlet boxes for wall partitions, floors, or roof and ceiling assemblies, consider which of these 3 categories of fire-resistant assemblies you’re dealing with:
- Fire partitions – the least restrictive fire wall with a minimum fire-resistance rating of 1 hour
- Fire barriers – an assembly of fire wall materials for walls rated between 1 and 4 hours
- Fire wall – the most restrictive fire resistant-rated assembly that has a 2-hour minimum and 4-hour maximum rating.
These ratings cover fire-resistive walls that are either load-bearing, structural walls or non-structural (non-load-bearing) – with framing that is either wood or steel studs.
Allied Moulded Products exclusively manufactures fiberglass electrical wall boxes that can be mounted with 3″ horizontal separation in all U-300 series walls without the need for additional insulation or putty pads. We also provide fiberglass ceiling boxes that can be placed 5-1/2″ center-to-center of each other in solid wood or pre-engineered wood joist fire-resistive ceiling assemblies.
Benefit of Allied Moulded fiberglassBOX
Electrical contractors choose our fiberglassBOX™ series of FRP wall boxes because they can be safely mounted within 3 inches of each other in opposing U300 wall assemblies. Compare this to the 2 feet requirement for metal and PVC electrical boxes. Other benefits of our fiberglass electrical boxes for fire resistive walls include:
- Reduced installation costs – No additional fire protection components like putty pads, insulation, or mineral wool are required, saving you in both labor and material costs.
- Superior mechanical properties – Fiberglass has an excellent temperature range and the ability to withstand loads and impact, and is suitable for corrosive environments
- Install more with less space – UL tested and rated for 2-HR fire-resistive walls, these boxes allow for a closer spacing of 3″ and are available up to and including three-gangs FRP wall boxes.
- Shorter cable runs – Electricians can place multiple FRP electrical boxes in a single cavity, which significantly reduces the amount of nonmetallic sheathed cable required.
- Best for housing electronics – Fiberglass electrical enclosures are non-conductive and the material is transparent to radio frequencies, making them perfect for A/V equipment.
- Suited for wet locations – Use fiberglass electrical boxes for industries that are often hosed-down, such as food and beverage processing, car washes, and outdoor installation.
- Harsh outdoor installations – Because fiberglass does not contract or expand with stress, cold, or heat, FRP boxes are the best choice when exposed to inclement weather.
When choosing a fire-resistive, electrical box, always look for the UL Classification Marking on the box, along with the hourly rating which may state Class 1 or 2HR. Also, make sure the box indicates which type of assembly it is to be used for. This will typically be designated as “F” for floor, “W” for wall; “C” for ceiling; and “F/C” for floor/ceiling.
Always refer to the UL Electrical Construction Equipment Directory and Fire Resistance Directories for details describing which boxes are classified for use in specific fire-rated assemblies.
Learn more about Allied Moulded Products fiberglassBOX fire resistive rating here.