Division 23 Heating, Ventilating, and Air Conditioning (HVAC)

Detail or Installation Mismatch in Division 23 Heating, Ventilating, and Air Conditioning (HVAC) submittals

By Deviation Check Editorial Team. Last reviewed June 1, 2026.

Short answer

The submitted detail, dimension, anchorage, or installation method differs from what the spec or drawings require. Default grade in Division 23 Heating, Ventilating, and Air Conditioning (HVAC): Fix and Resubmit.

The submitted detail, dimension, anchorage, or installation method differs from what the spec or drawings require. This guide covers how it shows up specifically in Division 23 Heating, Ventilating, and Air Conditioning (HVAC) submittals.

What to look for in Division 23 Heating, Ventilating, and Air Conditioning (HVAC)

  • Duct gauge lighter than spec (e.g., 22ga where spec requires 20ga for high-pressure duct)
  • Duct connection type (flanged vs slip-and-drive vs welded)
  • Pipe material mismatch (Type L vs Type M copper, Schedule 40 vs 80 steel)
  • Pipe joining method (brazed vs soldered, press-fit vs threaded vs welded)
  • Hanger/support spacing exceeds spec or SMACNA maximums
  • Insulation type (closed-cell vs fiberglass, vapor barrier presence)
  • Drain piping size or material differs
  • Vibration isolation type or deflection rating differs from schedule
  • Refrigerant line sizing differs from manufacturer requirements
  • Controls wiring type or protocol differs (BACnet vs Modbus vs proprietary)
  • Access door size or location differs from spec requirements
  • Seismic bracing method or spacing differs

How severe is it?

Default grade: Fix and Resubmit. Escalates to Blocker when the difference affects a fire-rated, seismic, or structural assembly.

Deviation Check assigns a default per category and escalates or de-escalates based on the spec, always showing its reasoning. See the Division 23 severity rules.

What the PM should do

Stamp the submittal Revise and Resubmit. Mark the deviation, return the relevant spec passage as a redline, and have the sub correct and re-send before fabrication or installation.

Back to the Division 23 Heating, Ventilating, and Air Conditioning (HVAC) hub, browse all divisions, or start a review.

Frequently asked questions

What duct and pipe detail mismatches appear most often in Division 23 HVAC submittals, and which ones escalate beyond a standard Fix and Resubmit?

Duct gauge lighter than spec - for example 22 gauge where 20 gauge is required for high-pressure duct - and pipe material mismatches such as Type L versus Type M copper or Schedule 40 versus Schedule 80 steel are the most common. Any mismatch that affects a fire-rated, seismic, or structural assembly escalates to Blocker; seismic bracing method or spacing differences and hanger and support spacing that exceeds SMACNA maximums fall into that category.

How does controls wiring and protocol affect the detail or installation mismatch review in Division 23 HVAC submittals?

The submittal must show controls wiring type and protocol matching the spec - BACnet, Modbus, or a named proprietary protocol are not interchangeable. Refrigerant line sizing must also follow manufacturer requirements, not just general practice. Vibration isolation type and deflection rating must match the schedule, and pipe joining method - brazed versus soldered, press-fit versus threaded versus welded - must match the specified method before the package can advance.

View this page as Markdown for LLMs and note-taking.