Class A Loop Broken by a Remodel
A hospital wing has an addressable signaling line circuit wired as a Class A loop serving 40 smoke detectors and 12 monitor modules. A renovation contractor cuts one leg of the loop to install a new wall and splices it back with wire nuts inside a junction box that is then buried behind new drywall with no accessible cover. The system continues to operate normally because the loop is Class A and survives a single open. During a later inspection, the buried splice is discovered. The contractor argues that because the system still works and Class A tolerates a single break, the splice is acceptable. The facility wants to avoid reopening the wall.
1. Evaluate the contractor's argument that Class A survivability makes the buried splice acceptable.
Read the worked answer
Class A survivability means the circuit continues to function with a single open or ground fault; it does not permit abandoning a splice in an inaccessible location. Splices and connections must be made in listed enclosures that remain accessible for inspection, testing, and maintenance, and must use approved means. Burying a wire-nut splice behind drywall violates installation requirements and defeats future troubleshooting and testing. The fact that the system still operates masks a latent defect: a second fault on the loop would take down devices, and the buried connection is not inspectable. The AHJ should reject the installation and require the splice to be relocated to an accessible, listed junction box, or the circuit to be rerouted without a concealed splice.
2. What testing and documentation should be required after the correction?
Read the worked answer
After relocating the splice to an accessible listed enclosure, require: (1) verification that the loop is restored to a complete Class A configuration with no concealed connections; (2) a full retest of the affected SLC, including device communication for all 52 points and a single-open survivability test if the design intends Class A operation; (3) confirmation that no other concealed splices exist in the renovated area; (4) updated as-built drawings showing the new junction box location; and (5) documentation of the test results in the inspection record. The AHJ may also require the contractor to demonstrate that the loop's fault tolerance is intact after the repair.