Middle Atlantic 2337A-WH Round Non-Metallic External Mounting Box

The Middle Atlantic 2337A-WH is a 5 1/2" [140mm] diameter round external box built to give smoke detectors, fire alarm devices, and other wall- or ceiling-mounted security hardware a clean, code-appropriate backing surface. It's a non-metallic (NM) box from the 2300 Series, sized for standard 3 1/2" [89mm] or 4 1/16" [103mm] mounting centers — the two hole patterns you'll find on the overwhelming majority of commercial smoke and fire alarm bases. If you're specifying backboxes for a fire/life-safety retrofit or a new intrusion/security device rollout, the 2337A-WH (often searched as 2337A WH) is the kind of unglamorous part that determines whether your install day goes smoothly or turns into a trip back to the supply house.

Overview

This is a surface-mount external box, not a recessed or in-wall unit — it has an open base, meaning it mounts flush to the wall or ceiling surface and the device attaches directly to the box rather than into a finished wall cavity. That open-base design is a deliberate simplification: it skips drywall cutting and stud-cavity work entirely, which matters on retrofit jobs where you're adding a smoke detector or security device to an existing ceiling and don't want to open up finished surfaces. The white finish is intended to blend into painted ceiling tile and drywall rather than stand out as an obvious add-on.

Key Features

• Dual mounting center support (3 1/2" and 4 1/16"): Covers both common device hole spacings, so you don't need to stock two different box SKUs to match whatever smoke detector or alarm base shows up on the BOM.
• 5 1/2" [140mm] diameter: Gives enough surface area to fully back common round security and alarm device bases without the device overhanging the box edge — reduces the chance of a device that wobbles or pulls loose from drywall anchors alone.
• Non-metallic (NM) construction: Lighter than a comparable steel box and won't conduct electrical faults into the mounting surface — a practical fit for low-voltage security and alarm circuits where you don't need EMT/conduit-grade metal enclosures.
• Open base design: Surface-mounts directly to wall or ceiling without cutting into the cavity behind it — faster install on retrofit and add-on device runs.
• White color finish: Matches standard ceiling tile and painted drywall so the box doesn't visually compete with the device it's backing.
• Purpose-built for hanging fixtures, smoke/fire alarms, and other security devices: This is a device backbox, not a general electrical box — do not use it to support ceiling fans, which the manufacturer specifically excludes due to the dynamic load a spinning fan puts on the mount.

Integration & Compatibility

Because the 2337A-WH supports both 3 1/2" and 4 1/16" mounting centers, it's compatible with the two hole-pattern standards used across most commercial smoke detector and fire alarm device bases — check your specific device's mounting-center spec before ordering to confirm which pattern it uses. This box is part of the broader lineup of Middle Atlantic products, and it pairs naturally with the mounting hardware and enclosures found in a build-out that also draws from cable management components. If you're speccing backboxes as part of a larger surveillance or intrusion detection rollout, it's worth cross-referencing against your video surveillance device list so box quantities match device counts exactly, and reviewing a general PoE and low-voltage planning guide if the same run includes powered security devices. For device runs that include electrical enclosures rather than round device boxes, the electrical enclosures category covers the metal-box side of a mixed job.

Frequently Asked Questions

Q: What mounting centers does the 2337A-WH support?

A: The 2337A-WH supports 3 1/2" [89mm] or 4 1/16" [103mm] mounting centers, covering the two most common hole patterns on commercial smoke/fire alarm and security device bases.

Q: Can I use the 2337A-WH to mount a ceiling fan?

A: No. The manufacturer specifies this box is not for use with fans.

Q: What is the diameter of the 2337A-WH?

A: 5 1/2" [140mm], with an open base design.

Q: Is the 2337A-WH metallic or non-metallic?

A: Non-metallic (NM) construction.

Q: What color does the 2337A-WH come in?

A: White.

Q: Is the 2337A-WH TAA compliant?

A: Yes, the 2337A-WH is TAA compliant.

Marty Allison

The 2337A-WH is the kind of part that shows up on a BOM in bulk, and the spec that actually matters here is the dual mounting-center support — 3 1/2" and 4 1/16" — because it's the difference between one box SKU covering your whole device list or two.

Technical Highlights:

• Dual mounting centers (3 1/2" / 4 1/16"): lets one box SKU back the two most common commercial smoke/alarm device hole patterns instead of forcing you to stock and track two separate part numbers.
• 5 1/2" [140mm] diameter, open base: enough surface area to seat standard round device bases flush without overhang, and the open base skips cavity cutting on retrofit jobs.
• Non-metallic construction: lighter in hand than a steel equivalent and doesn't introduce a grounding path concern on low-voltage security circuits.

Deployment Considerations:

• Confirm your device's actual mounting-center spec before ordering — 2337A-WH covers 3 1/2" and 4 1/16" only, not every alarm base pattern on the market.
• The manufacturer explicitly excludes fan use — don't substitute this into a ceiling fan box role even if the diameter looks close; it's not rated for that dynamic load.

On a fire/life-safety retrofit where you're adding smoke detectors to finished ceilings without cutting drywall, the 2337A-WH's open-base surface mount and white finish make it a straightforward, low-disruption backbox choice — just verify device hole spacing against the 3 1/2"/4 1/16" pattern first.