21.1 Installing by Tonnage & Class A vs Class B Limits
Key Takeaways
- F.S. 489.105(3)(g) limits Class B to 25 tons of cooling and 500,000 Btu of heating in any one system; Class A under 489.105(3)(f) is unlimited in capacity.
- The Class A Trade C outline scores installing systems of 25–100 tons and over 100 tons plus centrifugal compressors; the Class B outline omits those install items but still covers under-25-ton systems and absorption theory.
- “Any one system” follows the connected plant, not the building: two 20-ton chillers on one common chilled-water loop are 40 tons and outside Class B.
- Dead load is the scheduled operating weight plus water fill; live load is service occupancy. New building power wiring is not HVAC Class A/B work — F.S. 489.105 fences power to dedicated HVAC circuits, existing single-phase disconnects, and low-voltage controls.
- One refrigeration ton is 12,000 Btu/h; compressor capacity is read from expanded data at the actual suction and discharge temperatures, not from a frozen nameplate.
21.1 Installing by Tonnage & Class A vs Class B Limits
Trade Area C (Installation of Refrigeration and HVAC Systems) is 23 percent of the Class A trade exam and 22 percent of Class B. After packaged splits and heat pumps, the Class A outline walks systems under 25 tons, systems of 25 to 100 tons, and systems over 100 tons. Class B keeps the under-25-ton install cluster and drops the 25–100 and over-100 install items, along with centrifugal compressor systems. Absorption stays on both outlines. Ammonia is a Class A Trade C item. The 2026 Air Conditioning CBT books that support this chapter are Refrigeration & Air Conditioning Technology, 9th Edition (2021), Florida Building Code — Mechanical, 2023, and Pipefitters Handbook, 3rd Edition (1967) for the hydronic side. F.S. 489.105 is the statute that decides who may contract the job before a bolt is turned.
Quick Answer: Class B may install one system of not more than 25 tons cooling and 500,000 Btu heating. Class A is unlimited. Count the connected plant, not the number of cabinets. Dead load comes from the operating-weight schedule. Compressor tons come from the expanded-data table. New building feeders are an electrical contractor.
Why tonnage class is a license line, not a catalog row
A refrigeration ton is 12,000 Btu/h. Twenty-five tons is 300,000 Btu/h of cooling. Five hundred thousand Btu of heating is a separate cap, not a conversion of the cooling number. A rooftop that is 20 tons cooling with a 600,000 Btu gas or hydronic heating section already breaks Class B on heat, even though cooling is under 25 tons. A 30-ton chilled-water air handler with a 400,000 Btu heating coil breaks Class B on cooling. Both numbers in F.S. 489.105(3)(g) must fit, and they must fit in any one system.
Class A (F.S. 489.105(3)(f)) is unlimited in that capacity. Class A also picks up boilers, unfired pressure vessels, pressure and process piping, and pneumatic control piping that Class B’s definition does not list. Class B still installs piping and insulation of pipes, vessels, and ducts, hydronic coils, and packaged machines inside the 25-ton / 500,000 Btu fence.
DBPR’s Class A experience path wants one year on systems in excess of 25 tons cooling and 500,000 Btu heating. That is why this chapter still teaches Class B candidates the large-plant theory: the upgrade to Class A is an experience-and-outline step, not a new physics.
What “any one system” means on a bid
The exam’s favorite trap is treating “25 tons” as a building total or as a nameplate per compressor. The statute says any one system. A system is the connected refrigeration or hydronic plant that serves the load as one machine.
| Arrangement | Cooling count | Who may contract it |
|---|---|---|
| One 20-ton packaged rooftop, 400,000 Btu heat | 20 tons / 400,000 Btu | Class A or Class B |
| One 40-ton packaged rooftop | 40 tons in one cabinet | Class A only |
| Two 20-ton rooftops, separate refrigerant circuits and separate duct systems, each under 500,000 Btu heat | Two 20-ton systems | Class A or Class B |
| Two 20-ton chillers piped to one common chilled-water loop | 40 tons, one system | Class A only |
| One 80-ton water-cooled chiller | 80 tons | Class A only (25–100 ton install item) |
| One 250-ton centrifugal | 250 tons | Class A only (over 100 tons and centrifugal) |
| One 15-ton lithium-bromide absorption chiller | 15 tons | Class A or Class B (absorption is on both outlines) |
| One 60-ton absorption machine | 60 tons | Class A to install; Class B still owes the theory |
Worked capacity check. An Orlando medical office wants an 80-ton water-cooled chiller. Cooling load = (80 \times 12{,}000 = 960{,}000) Btu/h. That is more than three times the Class B cooling cap. Putting two 40-ton barrels on a common evaporator header does not create two systems — it is still one 80-ton plant. Splitting the building into two independent 20-ton DX rooftops, each with its own duct and its own heating section under 500,000 Btu, is two systems and is Class B work. The drawings, not the salesperson’s “we’ll call them separate,” decide.
Dead loads, pads, and what the structure must already hold
Dead load is the weight of permanently installed equipment and the water (or glycol) that stays in it. Live load is people, tools, rain, and maintenance occupancy on a roof or platform. Chapter 18.4 already used that split for rooftop units and rigging; large chillers and towers are the same rule at a heavier number.
Read the equipment schedule: shipping weight is not operating weight. Operating weight includes water fill in the evaporator, condenser, and (for a tower) the basin. An 80-ton water-cooled machine plus an induced-draft tower is a structural number on the housekeeping pad or steel dunnage, not an HVAC field guess. Vibration isolators, inertia bases, and seismic/wind restraints do not reduce the dead load the beam must carry — they change how that load is applied. If the structural sheet does not support the scheduled operating weight plus the service live load on the pad, that is an RFI, not a Friday set.
Florida rooftop towers and large RTUs also take wind load. FBC Mechanical still wants listed equipment and access. Hurricane straps and curb ratings come from the listing and the structural design. OSHA 29 CFR 1926.251 still wants tagged slings inspected each shift when that 80-ton barrel comes off the truck (Chapter 18.4).
Wiring on a large plant — stay inside 489.105
An 80-ton chiller is almost always three-phase, commonly 460 V, with a nameplate MCA (minimum circuit ampacity) and MOCP (maximum overcurrent protection). F.S. 489.105(3)(f) and (g) let Class A and Class B:
- Replace, disconnect, or reconnect power wiring on the line or load side of a dedicated existing electrical disconnect on single-phase systems.
- Repair or replace power wiring, disconnects, breakers, or fuses for dedicated HVAC circuits with a circuit-breaker lock.
- Install, disconnect, and reconnect low-voltage HVAC control wiring.
The same definitions do not include electrical power wiring as a new building trade. A new feeder from the switchgear to a new 460-volt chiller disconnect is an electrical contractor. HVAC still reads MCA/MOCP so the specified breaker matches the listing, still lands control wiring (flow switches, enable, interlocks, DDC), and still uses a lock on a dedicated HVAC breaker when working the circuit. Pneumatic control piping to large valves remains Class A only.
Compressor capacity is a table, not a cabinet stencil
Nominal “80 tons” is a rating-test point. Expanded performance data list capacity at a saturated suction temperature (SST) and saturated discharge temperature (SDT) — or at evaporator and condenser leaving-water temperatures on a chiller. Capacity falls when condensing temperature rises (dirty tower, high Florida wet-bulb, low condenser gpm) or when suction temperature drops (starved evaporator, low chilled-water flow). Capacity rises when SST rises and SDT falls.
Worked table read. The schedule says 80 tons. The manufacturer’s page at 44°F leaving chilled water and 95°F leaving condenser water shows 76 tons. Design capacity is 76 tons, not 80. Unloaders, slide valves, inlet vanes, or a VFD reduce capacity to match a part load; they do not restore the tons the condenser is not rejecting. Under-25-ton DX uses on/off or staging; 25–100 ton plants often use multiple compressors or a screw with a slide valve; over 100 tons is where centrifugal machines appear (Section 21.3) — and where the Class B outline stops scoring the install.
Florida scenario
Sunrise Mechanical holds a certified Class B license in Orange County. A property manager asks for a turnkey 80-ton water-cooled chiller, two primary pumps, an induced-draft tower, and a 20-ton DX rooftop on a remote annex. The 20-ton annex, if it is its own refrigerant circuit and duct system and its heat is under 500,000 Btu, is inside Class B. The 80-ton plant is not: 80 > 25, it is a 25–100 ton Class A install item, and the two compressors in that chiller do not split it into two 40-ton “systems” while they share one evaporator barrel and one building loop. Sunrise cannot contract the plant as Class B, cannot pull the mechanical permit on that ticket, and cannot “sub the barrel to a helper with a Class A card” while remaining the qualifier. The shop either holds Class A, works under a Class A or mechanical qualifying agent, or leaves the 80-ton scope. The Class B candidate still has to read the 76-ton expanded-data row, the 192 gpm chilled-water flow at 10°F ΔT (Section 21.2), the dead-load note on the pad, and the 460-volt MCA — because the Class A upgrade, and a fair number of Class B theory items, still live on that drawing.
Traps: (1) Treating 25 tons as a building total instead of per system. (2) Ignoring the 500,000 Btu heating cap because cooling is under 25 tons. (3) Calling two chillers on one loop “two systems.” (4) Using shipping weight as dead load. (5) Running a new 3-phase feeder on an HVAC ticket. (6) Believing Class B may skip large-plant theory because the outline dropped the install bullets.
Under F.S. 489.105, which capacity rule governs a Class B air-conditioning contractor?
A Class B qualifier is asked to install two 20-ton water-cooled chillers that share one common chilled-water loop serving a single office building. Which statement matches the statute and the Class A/B outlines?
An 80-ton water-cooled chiller is scheduled at 460-volt three-phase. The expanded-data sheet at the design water temperatures shows 76 tons. Which installation statement is accurate for the Florida HVAC contractor exam?