8.1 Scheduling Trade Operations (CPM, RFI & Submittals)
Key Takeaways
- Business & Finance Area C (Managing Trade Operations) is 10% of the 120-question B&F exam; CPM, delivery and manufacture times, RFIs, trade sequencing, and submittal/approval/fabrication are the first cluster.
- On a CPM network, activities with zero total float form the critical path; delaying a critical activity delays project completion by the same number of days.
- HVAC factory lead time starts after submittal approval or approved-as-noted, not when the package is mailed; Revise and Resubmit keeps manufacture from starting.
- An RFI is a written question when documents conflict or are unbuildable; a change in scope, time, or price is a change-order path, not a silent field fix.
- SMACNA duct construction data (pressure class, seal class, gauge, reinforcement) and equipment performance data are typical HVAC submittals; FBC Mechanical 2023 inspections are scheduled activities with predecessors.
8.1 Scheduling Trade Operations (CPM, RFI & Submittals)
Business & Finance (B&F) Area C — Managing Trade Operations is 10% of the 120-question B&F exam, roughly a dozen scored items. The first cluster is not a motivational calendar. It tests whether a qualifying agent can sequence work with the critical path method (CPM), honor delivery times and manufacture times, write and close requests for information (RFIs), and drive submittals through approval into fabrication before a crane sits on a Florida school roof. The 2026 B&F references that carry this cluster are the Contractors Manual 2025 (used beginning February 1, 2026) and AIA A201-2017. On the HVAC trade list, SMACNA HVAC Duct Construction Metal and Flexible, 4th Ed. 2020 is the duct-construction book the submittal will cite. Class A and Class B candidates sit the same B&F paper. A 40-ton packaged rooftop is outside Class B scope under F.S. 489.105 (25 tons of cooling and 500,000 Btu of heating in any one system), but Class B still has to schedule the 20-ton jobs the license can take.
Why the schedule is a qualifying-agent problem
Under F.S. 489.1195, the primary qualifying agent is jointly and equally responsible for supervision of all field work at all sites. A late rooftop unit (RTU) is not only a cash-flow problem. It strands roofers, electricians, and a crane subcontractor, burns liquidated damages, and leaves mechanical inspections uncalled under the Florida Building Code — Mechanical, 2023 (8th Edition — the listed exam edition). HVAC sits on someone else's critical path: the roof must be ready for curbs, the structure must take the operating and rigging load, the electrical service must be there for the dedicated disconnect, and the authority having jurisdiction (AHJ) must see the rough-in before the ceiling closes.
CPM, float, delivery, and manufacture
CPM is a network of activities with durations and predecessor logic, not a bar chart drawn after the fact. Each activity has an early start (ES), early finish (EF), late start (LS), and late finish (LF). Total float equals LS minus ES (or LF minus EF). Activities with zero float are on the critical path. Delay a critical activity one day and the project finish date moves one day. Delay a non-critical activity inside its float and the finish date does not move.
The forward pass computes the earliest each activity can finish. The backward pass works from the required finish date. The longest path through the network is the critical path. Use the duration convention the exam stem gives; many contractor-exam problems treat the next activity as starting after the predecessor's duration is consumed.
Worked HVAC CPM. Coastal Air is the mechanical sub on a school RTU replacement:
| Activity | Duration | Predecessors |
|---|---|---|
| A — Shop drawings, SMACNA duct data, and equipment submittals | 12 days | None (start) |
| B — Architect/engineer review and any resubmittal | 10 days | A |
| C — Factory manufacture and freight of 20-ton RTUs | 40 days | B |
| D — Roof curbs and structural steel | 6 days | Roof released (can run parallel with A–C) |
| E — Crane, rigging, and set | 1 day | C and D |
| F — Refrigerant piping, condensate, and power wiring on the dedicated disconnect | 8 days | E |
| G — Start-up, TAB, and mechanical inspection | 3 days | F |
If curb work (D) can start on day 1, it finishes on day 6. Submittals plus review plus factory (A+B+C) equal 62 days before the units exist to fly. The crane (E) cannot start until both C and D are done, so E waits on C, not on D. D has 56 days of float (62 − 6). The critical path is A–B–C–E–F–G = 12 + 10 + 40 + 1 + 8 + 3 = 74 working days. Ordering the crane for week 3 because the roof is ready is how you pay a show-up fee and still have no unit.
Delivery times and manufacture times are activities, not margin notes. A 20-ton packaged RTU is not a warehouse commodity in peak Florida cooling season. Custom curbs, coated coils, special voltage, and energy-code ratings add factory days. Refrigerant allocation under the federal HFC phasedown (AIM Act) affects cylinder supply and pre-charged equipment availability. Do not invent a GWP number the stem did not give; do put the vendor's written ship date on the network. If the factory quotes 40 days after approved submittals, the clock does not start the day you mailed the package. It starts when the architect's stamp is Approved or Approved as Noted and you have released the order.
RFIs: when the drawings cannot be built as drawn
A request for information (RFI) is a written question to the design team when the contract documents are silent, conflicting, or unbuildable. It is not a change order, not a submittal, and not a complaint. HVAC RFIs fire when the structural drawing's RTU opening does not match the mechanical schedule's curb; when the electrical one-line shows a 208-volt three-phase disconnect and the specified unit is 460-volt; when duct mains collide with a fire-rated shaft, a grease duct under NFPA 96 (2021), or a beam that was never on the mechanical sheet; or when the specified refrigerant is no longer the factory's production refrigerant.
AIA A201-2017 (on the 2026 B&F list) puts the contractor on the documents: review them, report errors promptly, and do not proceed with work you know is at variance. An unanswered RFI is a schedule risk — log the date sent, the date due, and the activity it gates. If the answer changes scope, price, or time, that is a change order path, not a silent field fix. A Class A shop setting a 40-ton unit on a custom steel frame is more likely to find a structural conflict than a Class B 5-ton changeout; Class B still needs the RFI procedure because B&F questions are not split by tonnage.
Submittals, approval, fabrication, and trade sequence
Submittals are the contractor's proof that the product and the shop method match the specifications. Typical HVAC packages:
- Equipment — performance data, AHRI listings, efficiency as specified, curb drawings, weights for structural and crane planning, electrical characteristics, and refrigerant type.
- SMACNA duct — pressure class, seal class, material, gauge, reinforcement spacing, and flexible-duct limitations from SMACNA HVAC Duct Construction Metal and Flexible, 4th Ed. 2020 (fibrous glass from the 8th Ed. 2021 when that is the spec).
- Controls, TAB, and close-out — sequences, reports, O&M manuals, as-builts, and owner training.
The sequence the exam cares about is submit → review/approval → fabricate or release → deliver → install. Fabricating duct or releasing an RTU from the factory before approval is how you own a pile of wrong-gauge duct and a 20-ton unit that will not sit on the specified curb. Approved as Noted usually lets fabrication proceed if the notes are incorporated. Revise and Resubmit does not. Put resubmittal time back on the CPM.
Sequencing trades is physics and OSHA, not courtesy. Roofing and curb flashing before the crane day. Structural steel and housekeeping pads before a chiller lands (Class A work when the system exceeds 25 tons or includes boilers or unfired pressure vessels). Electrical lockout of the dedicated HVAC circuit before changeout. Crane and rigging (OSHA 1926 Subpart CC) need a pick plan, a competent person, a weather window, and street or right-of-way permits if the boom occupies a Florida DOT or municipal lane. You cannot TAB a system the AHJ has not seen after the ceiling has already closed.
Permit inspections as scheduled activities
Florida mechanical work is inspected under FBC Mechanical 2023 and FBC Energy Conservation 2023. Treat inspections as activities with predecessor logic: rough duct and refrigerant piping before concealment, above-ceiling before close-in, final after start-up. A two-day wait for an inspector is float only if you put it in the network. Energy forms and AHRI data that were in the submittal are what the inspector will look for; they are not a close-out surprise.
Florida HVAC scenario
Orlando Comfort, a Class A certified contractor, is the mechanical sub on a 12-unit school RTU replacement. Each unit is 15 tons — inside Class B if they are truly separate systems; this shop is Class A. The general contractor's CPM shows mechanical complete in 60 calendar days. The factory's written lead time is 45 days after approved submittals. Architect review is 10 days in the spec. Submittal preparation is 8 days. Eight plus 10 plus 45 equals 63 days before the units ship, plus freight, plus a Saturday crane. The HVAC qualifier who knows we can make 60 days without crashing review or paying a premium factory slot is not managing trade operations — they are bidding a schedule the network already proves is impossible. The correct move is an RFI or schedule notice to the general contractor before the steel hits the ground, not a hope that the crane will wait.
A school RTU replacement CPM shows: submittals 12 days; design review 10 days after submittals; factory manufacture 40 days after approval; curb and steel 6 days that can start immediately; crane set 1 day after both manufacture and curbs. Which statement is correct?
The mechanical specifications require SMACNA duct-construction data and RTU performance data as submittals. The factory lead time is 40 days after an approved submittal. Which statement is correct?
Structural drawings show a 42-inch RTU opening. The mechanical schedule and the approved equipment submittal need a 54-inch curb. What is the correct operations document?