Sequence of Operations
HVAC · Controls Narrative
Modes
1
Drafts
1
Zones
0
Setpoints OK
0/0
To resolve
1
ASHRAE Guideline 36 modes · 90.1 setpoint checks1 to resolve
1The system this narrative describesThe equipment tag and system type, written the way the schedule writes it — for example a tag, then a slash, then the system description. Whatever precedes the first slash or comma is used as the equipment tag inside the generated narrative, so the paragraphs name this unit rather than "the system".System not named · Zone 4A
System designationThe equipment tag and system type, written the way the schedule writes it — for example a tag, then a slash, then the system description. Whatever precedes the first slash or comma is used as the equipment tag inside the generated narrative, so the paragraphs name this unit rather than "the system".
Climate zoneThe ASHRAE / IECC climate zone for the project site — the number is the thermal zone and the letter is the moisture regime (A moist, B dry, C marine). It decides the economizer high limit, which is stated below and folded into the economizer and cool-down narratives.
Economizer high-limit deviceASHRAE 90.1 Table 6.5.1.1.3 (reprinted as IECC Table C403.5.3.3) sets the high-limit shutoff by climate zone and sensing device. Fixed dry bulb is 75 °F in the dry and cold zones (1B, 2B, 3B, 3C, 4B, 4C, 5B, 5C, 6B, 7, 8), 70 °F in 5A and 6A, and only 65 °F in the warm-humid A zones (1A, 2A, 3A, 4A). Differential dry bulb is not permitted at all in 1A, 2A, 3A or 4A. The enthalpy options apply everywhere and carry a 28 Btu/lb limit with a 75 °F dry-bulb backstop. Pick the zone and device and the required shutoff condition is written into the economizer mode narrative for you.
Required high-limit shutoffautoASHRAE 90.1 Table 6.5.1.1.3 (IECC Table C403.5.3.3)
Economizer off when outdoor-air dry bulb > 65 °F
Capacities & safety set pointsNothing set
Supply CFMThe design supply airflow. It is a plain schedule value, not a code check: NFPA 90A puts a duct smoke detector downstream of the filters on any supply system over 2000 CFM, which essentially every commercial air handler clears, so a pass/fail on it would tell you nothing. The figure is quoted alongside that threshold in the smoke shutdown narrative instead, together with the NFPA 90A return-side rule (over 15000 CFM serving more than one story) and the note that the local IMC §606 amendment may differ.optional
Freezestat °FThere is no single code-published freezestat trip point, so this field is left free-text on purpose. Trip points depend on the coil, the glycol concentration, and the manufacturer's written instructions — field-verify the value and the capillary routing rather than copying a number from another project. What the sequence should say is fixed regardless: on a trip the fan stops, the outdoor-air damper closes, the heating valve opens, and the trip latches until it is manually reset. Enter a value and it is written into the freeze protection narrative with that field-verify note attached.optional
High static limitHigh and low duct static limits protect the ductwork and the fan, and their set points come from the duct construction class in the project specification rather than from a code table. Enter the project values.optional
Low static limitoptional
2Prepared by & project ownerThe engineering firm that prepared the narrative, and the owner or building it was prepared for. The licence that appears on the sealed document is the engineer of record's cert number in the document step, not a company trade licence.Not filled in
Prepared by
Project / owner
3Operating modes — the narrativeASHRAE Guideline 36, "High-Performance Sequences of Operation for HVAC Systems", defines the zone-group modes this builder starts from: Occupied, Warm-Up, Cool-Down, Setback, Setup, Freeze Protection and Unoccupied. Guideline 36 also drives set points from zone requests using trim-and-respond, so the supply-air temperature and duct static pressure follow the worst-case zone instead of sitting at a fixed design value. Every preset in "Add mode" arrives pre-written and rewrites itself around your equipment tag, your economizer high limit and your scheduled set points as you enter them. It is a DRAFT: until you edit a paragraph it is labelled as one in the export, because starter wording nobody has read is not a specification.1 mode · 1 still draft
Mode & triggerASHRAE Guideline 36, "High-Performance Sequences of Operation for HVAC Systems", defines the zone-group modes this builder starts from: Occupied, Warm-Up, Cool-Down, Setback, Setup, Freeze Protection and Unoccupied. Guideline 36 also drives set points from zone requests using trim-and-respond, so the supply-air temperature and duct static pressure follow the worst-case zone instead of sitting at a fixed design value. Every preset in "Add mode" arrives pre-written and rewrites itself around your equipment tag, your economizer high limit and your scheduled set points as you enter them. It is a DRAFT: until you edit a paragraph it is labelled as one in the export, because starter wording nobody has read is not a specification.
Scheduled occupied period for the zone group served by the system, or an active after-hours override.
Draft
4Setpoint scheduleASHRAE 90.1 §6.4.3.1.2: where one thermostat controls both heating and cooling, the two set points must be separately adjustable with a dead band of at least 5 °F between them, inside which heating and cooling energy is shut off or reduced to a minimum. A heating set point within 5 °F of the cooling set point is a code violation, and in practice it makes the two loops fight each other. §6.4.3.3.2 adds the setback rule: the unoccupied heating set point must sit at least 10 °F below occupied heating, and the unoccupied cooling set point at least 5 °F above occupied cooling. A row reads OK only once all four of those checks have run and passed — open Details and fill the unoccupied pair, or the row stays "Not set".No zones yet
ZoneOcc heatOcc cool
Dead bandASHRAE 90.1 §6.4.3.1.2: where one thermostat controls both heating and cooling, the two set points must be separately adjustable with a dead band of at least 5 °F between them, inside which heating and cooling energy is shut off or reduced to a minimum. A heating set point within 5 °F of the cooling set point is a code violation, and in practice it makes the two loops fight each other. §6.4.3.3.2 adds the setback rule: the unoccupied heating set point must sit at least 10 °F below occupied heating, and the unoccupied cooling set point at least 5 °F above occupied cooling. A row reads OK only once all four of those checks have run and passed — open Details and fill the unoccupied pair, or the row stays "Not set".
ActionsZone
Occupied heat
Occupied cool
Not setNot set
5System description & alarmsThe paragraph that opens the narrative: what the system serves, its major components, and how it is zoned. One paragraph is enough — the mode sections carry the operating detail.Nothing written
System descriptionThe paragraph that opens the narrative: what the system serves, its major components, and how it is zoned. One paragraph is enough — the mode sections carry the operating detail.optional
Alarms & interlocksThe alarm points, their limits and their delays, plus every interlock between this system and another one. This is the list the commissioning authority checks off, so name the point as the BAS names it.optional
6Document & revisionThe revision block. Increment the revision on every reissue — a controls narrative gets marked up repeatedly during commissioning, and the revision is how the field knows which copy it is holding.SOO-2026-001 · Rev 0
Document number
Date
Rev.
Project name
Engineer of record
PE / cert #optional