The Deleted Duct Detector and a Code-Edition Mismatch

Start with the baseline rule, then test the exceptions. The adopted building code generally requires duct smoke detection on air-distribution systems exceeding 2,000 cfm that serve the protected space. At 4,000 cfm this unit is over the threshold, so detection is required unless a listed exception applies.

Test the exception, do not assume it. The common exception covers units that are 100% outdoor air and under 15,000 cfm. This unit appears to qualify on both counts - but only if you verify:

• the mechanical drawings truly show no return and no relief air reintroduced to the unit (a mixing box or an economizer return path kills the exception);
• nothing else in the code requires detection here - smoke-control systems, atria, certain occupancies, or an AHJ amendment;
• the local amendment list does not delete or narrow the exception.

Response: Do not grant the deletion on a cost basis. Grant it (if at all) on a written code basis: cite the exception, reference the mechanical drawing and the unit schedule proving 100% outdoor air, state that the designer concurs, and require AHJ written concurrence before the submittal is released. If any verification item fails, the duct detector stays.

Contract documents set the contractor's minimum; the adopted code sets the legal minimum. Where they differ, the contractor must satisfy the more stringent applicable requirement, and the designer must reconcile the documents.

Reasoning steps:

1. Identify the specific conflicts, not the editions in the abstract. Common edition-to-edition differences that matter here: documentation/submittal content, spot-detector spacing and wall-clearance rules, notification appliance audibility/candela criteria, battery and secondary-power calculation factors, and inspection/testing record requirements.
2. Compare requirement by requirement and note which document is stricter for each item.
3. Issue a written clarification (RFI response or bulletin) stating that the adopted code governs where it is stricter, and list the specific items affected so the contractor prices and installs the same scope the AHJ will inspect.
4. Do not accept 'the spec says the older edition' as justification for installing below the adopted code - the AHJ will not accept it, and the designer owns the resulting change order.
5. Document the resolution in the submittal review record so the as-built set and the inspection forms reflect what was actually installed.

Return it as incomplete; do not release it for installation.

• These are not optional niceties. Secondary-power (battery) sizing and appliance voltage-drop calculations are the design proof that the system will run 24 hours in standby plus the required alarm time, and that every notification appliance will see at least its listed minimum operating voltage at the end of the circuit under worst-case conditions.
• Without them the reviewer cannot tell whether the panel's charger, battery space, NAC ratings, and wire sizes are adequate - exactly the items an AHJ or commissioning agent will ask for.
• Mark the submittal "Revise and Resubmit," list the missing calculations as the reason, and state that no rough-in or device installation may proceed on the affected scope until the resubmittal is approved.
• Note that wire already pulled to an unapproved design is at the contractor's risk; if the calculation later forces a larger conductor, that is a contractor cost, not a change order, because the requirement was in the specification.