Refs: IMC 304.1-304.4; IMC 202; IECC; NFPA 30A; IBC (hazard/guards for context).
Plain English:
304.1 General: Install per approval + listing + manufacturer's instructions (MI) + IMC. Keep MI on site for inspection.
304.2 Conflicts: If code vs listing/MI conflict, IMC governs-except when IMC is less restrictive; then follow listing/MI.
304.3 Ignition source elevation: In public/private/repair garages, fuel-dispensing facilities, hazardous locations -> ignition source >=18 in above floor. Rooms that open directly to a private garage are part of the garage. Exception: FVIR-listed appliances (flammable-vapor ignition resistant) need no elevation.
304.3.1 Parking garages: Rooms with fuel-fired appliances connecting to a parking garage need a two-door vestibule; one door allowed if ignition source is elevated per 304.3. Exception: installs meeting 304.6.
304.4 Prohibited locations: No ignition-source equipment/appliances in Group H or control areas with open use/handling/dispensing of flammables/explosives.
On Plans: Why It Matters
Top redlines: MI not on site, wrong choice between IMC vs MI when they conflict, ignition sources too low in garages/adjacent rooms, missing vestibule separation, and placing ignition sources in Group H areas.
🧾 Where To Show It (sheet map)
M-001: "Install per listing + MI + IMC; MI on site. Conflicts per 304.2. Ignition sources >=18 in where required. Vestibule per 304.3.1 when a room with fuel-fired appliances opens to a parking garage. No ignition-source installs in Group H open-use areas."
M-101/...: Flag garage-adjacent rooms, show vestibule (two doors or elevation basis), annotate 18-in elevation or FVIR listing, and note hazard areas as "no ignition source."
M-501/502: Typical garage vestibule detail; elevated platform detail with dimensions; FVIR notation example.
M-601: Columns for Ignition Source Height (in), FVIR (Y/N), Vestibule (Y/N/NA), Location Type.
Code Path: Equipment Schedule and Installation Detail
Every piece of mechanical equipment on the schedule must reference an installation detail number or 'per manufacturer's installation instructions (MI)' on the drawing.
Installation detail must show: mounting method, vibration isolation type, service clearances on all sides and above, and utility connections (electrical, gas, drain, condensate).
M-001 must state 'All mechanical equipment installed per manufacturer's installation instructions - MI governs where IMC does not specify.'
Check: Installation Detail Completeness
Scan the equipment schedule for any unit without a reference to an installation detail or MI - every scheduled unit needs one.
Confirm the installation detail shows clearances on all four sides and above - reviewers check clearance dimensions against the appliance listing.
For gas-fired equipment, verify the utility connections shown on the detail include the gas shutoff, flexible connector (if applicable), and venting connection.
Review Risk:
A schedule that names a unit without linking its critical installation conditions to the applicable detail, listing, and manufacturer instructions weakens the approval path.
Clearance dimensions that match the schedule but conflict with adjacent equipment or structure shown on the duct plan are a common pre-occupancy correction.
Vibration isolation specified as spring isolators without spring rate and deflection confirmed for the equipment weight is a consistent submittal review flag.
Field Tip:
If the room communicates with a private garage, treat it as garage for 304.3.
For WH/furnace in or next to a garage: choose FVIR or provide 18-in elevation; add vestibule where 304.3.1 triggers.
When MI is stricter than IMC, follow MI; when MI is looser, follow IMC. Note the MI page on the schedule.
Masterbuild QA Lens
Level mounting, condensate control, and vibration isolation are installation baseline requirements, but they need to appear on the drawings - not just in the spec. Confirm the plans show: drain pan size and routing for every cooling coil, vibration isolator schedule with isolator type and static deflection, and level-mount note on equipment that is gravity-dependent.
Drawing / Submittal Check
For IMC 304 installation requirements (Part 1): every piece of mechanical equipment on the schedule must have a corresponding installation detail or a reference to the manufacturer's installation instructions on the drawing. Confirm the following are shown for each unit: mounting method, vibration isolation, service clearances (all four sides and above), and utility connections. Equipment schedules that list the unit without referencing an installation detail will get a comment.
Common Review Risk
The drawings identify equipment but omit the location-specific installation conditions, clearances, support, protection, utilities, and manufacturer requirements needed to install and inspect it.
When To Escalate
Escalate when the service clearance required by the manufacturer's installation instructions conflicts with the service clearance shown on the drawings - when the manufacturer requires more clearance than the design provides. Manufacturer clearance conflicts discovered after equipment is installed require either equipment relocation or AHJ acceptance of a reduced clearance with documented justification.
Special Exhaust Coordination
For specialty exhaust, start with the contaminant and source. Then confirm capture method, duct material, routing, discharge, separation, controls, and whether another consultant or AHJ review is required.
Duct System Coordination
Installation requirements set clearances, support intervals, and connection methods for ductwork near equipment. Coordinate duct routing so clearances to appliances and structural elements are maintained per this section.