Packaged Rooftop Unit RTU Shipping Container Ontario

By Christian LeBlanc, second-generation operator, and Paul LeBlanc, owner, Van Blanc Ent. Inc.

Reading time: about 14 minutes.

What Is a Packaged Rooftop Unit, and Why Do Containers Use Them?

A packaged rooftop unit is a single outdoor cabinet that does everything a building’s HVAC system has to do. Compressor, condenser coil, evaporator coil, indoor blower, gas or electric heat, and usually an economizer damper, all bolted into one steel shell that sits on the roof. The duct openings sit on the underside of the unit and connect into the building through a roof curb. One refrigerant line, one electrical drop, one gas line if it’s gas-electric.

Buyers ask us about RTUs more than any other HVAC option, and the reason is geometric. Hanging a split system on the long wall of an 8-foot-wide container steals interior space. An RTU goes on top: floor stays clear, walls stay clear, only interruption is two small duct collars in the ceiling.

Ontario buyers have a second reason. A packaged unit is built for weather that swings from minus 25 in January to plus 32 in July. Trane, Carrier, Lennox, and AAON all sell rooftop units rated for that band. If you are still weighing how to heat and cool a container at all, our complete guide to container heating and cooling in Ontario walks through where a rooftop unit beats the alternatives and where it does not.

Tonnage: How to Size a 3-Ton or 5-Ton RTU for a Container Office

The trade sizes packaged units in tons (one ton equals 12,000 BTU per hour cooling). Manufacturers sell 3-ton, 4-ton, 5-ton, 7.5-ton, and larger increments. Almost every container fit-out we deliver lands between 3 and 5 tons.

The rough rule for a well-insulated 20-foot or 40-foot office container is one ton per 400 square feet of conditioned space, scaled up for southern exposure, glazing, and people load. A 20-foot office container with 160 square feet of floor and spray foam to R-13 needs a 2.5-ton or 3-ton unit. A 40-foot container with 320 square feet, four to six occupants, and a couple of windows usually wants 4 tons or 5 tons. If you are still scoping the build itself, our breakdown of what goes into a turnkey container office covers the insulation and layout choices that set your cooling load. Mining bunkhouses with eight to ten sleepers and high latent load push toward 5 tons on a single unit or two 3-ton units on a duplex container.

One thing buyers underestimate: the heating side. Gas-electric RTUs in the 3 to 5-ton range pair 60,000 to 115,000 BTU of natural gas heat with the cooling capacity. For container offices on propane (rural and mining sites), the same units convert with a manufacturer-supplied conversion kit. Heat pump RTUs are an option but their capacity drops below minus 15, so most Ontario fit-outs still spec gas or electric resistance backup.

What Does the Roof Curb Do on a Container RTU Install?

The roof curb is a rectangular steel frame, six to fourteen inches tall, that sits between the container roof and the RTU. It does three jobs: raises the unit above the drainage plane, carries the duct openings (supply and return), and spreads the unit’s weight across a structural connection that the corrugated container roof cannot carry on its own.

Manufacturers sell brand-specific curbs sized to their unit footprints. A Carrier 48TC uses one curb, a Trane Foundation uses another. Mixing brands creates curb-adapter work: a custom-fabricated transition piece, welded from 14 to 18 gauge G90 galvanized steel, that translates a new unit’s footprint to an old curb’s footprint. Adapters add fabrication labour and show up whenever someone replaces a unit on an existing roof.

For a new container build, you avoid the adapter by ordering the curb that matches the unit. The fabricator welds the curb to the container roof through a reinforcement frame, seals every penetration with EPDM gasket and pitch pan, and the RTU drops on top with bolts through the curb flange.

Structural Reinforcement: Why a Container Roof Needs Steel Underneath

This is the part most container HVAC quotes leave out, and it’s the part that fails inspections. A standard container roof is corrugated steel sheet, roughly 2 mm thick, with eight transverse roof bows tying the two top side rails together. It carries snow load (about 300 kg/m² uniform per ISO 1496-1), but it is not designed for a 600 or 700-pound concentrated load sitting on a 45-inch by 80-inch footprint.

The fix is a steel reinforcement frame welded inside the container, directly under where the curb sits. Two parallel C-channels (typically 6-inch C-9 lb steel) running across the container width, welded to the top side rails at each end and to the corner posts. The C-channels transfer the RTU’s weight into the corner posts, which are engineered for 86,400 lbs of stacking load per ISO 1496-1 and easily carry a 700-lb HVAC unit plus 1,400 lbs of snow load plus a service technician on the unit cabinet.

Which RTU Brand Fits a Shipping Container: Carrier, Trane, or Lennox?

The big three packaged-rooftop brands in Ontario are Carrier, Trane, and Lennox. AAON is the engineered-premium option for schools and hospitals. Daikin, Goodman, and Heil round out the residential-grade lineup that crosses into light-commercial 3 to 5 ton.

For a single-container office in the 3 to 5-ton range, the realistic Ontario shortlist is Carrier 48TC or Trane Precedent. Both have parts availability across Ontario through Wolseley, Master Group, and HD Supply. Lennox is fine but the parts pipeline is slower in smaller Ontario markets, which matters when a compressor fails in February.

Ductwork, Supply Collars, and the Awkward Geometry of a 20-Foot Box

A packaged RTU has two duct openings on its underside: a supply (conditioned air going down) and a return (room air coming back up). On a container, you have 8 feet of interior width and roughly 7’9″ of interior height (8’6″ for high cube), which means the ductwork either runs exposed under the ceiling, drops into a soffit, or vanishes into a single bulkhead at the unit.

The cleanest approach for a 20-foot office container is a single supply collar at the unit location feeding a short trunk duct (insulated R-6 flex or sheet metal) with two to four ceiling diffusers spaced along the length. The return is one large filter-grille set into the ceiling near the unit, so the return path is short and the filter is accessible. For a 40-foot container the same approach scales: longer trunk, four to six diffusers, one or two filter-grille returns. The interior finishing that hides this trunk run is the kind of work covered in our rundown of common container modifications.

High-cube containers (9’6″ exterior height) give you an extra foot of headroom and let the ductwork drop more aggressively. Standard 8’6″ containers force the ductwork tight to the ceiling, which limits where lights, detectors, and emergency sprinklers can go. If headroom is tight on your build, our look at how high-cube and standard-height boxes compare is worth a read before you pick the shell.

Electrical Service, Condensate, and the Small Stuff That Stops Inspections

A 3-ton RTU pulls about 12 to 20 amps at 208/230V single-phase. A 5-ton pulls 22 to 28 amps single-phase or 12 to 15 amps three-phase. The electrical service to the container needs to handle the RTU plus interior lighting, receptacles, and any other equipment, which usually means a 100-amp single-phase or 60-amp three-phase main panel inside the container with a dedicated breaker for the rooftop unit.

The electrical work is handled by the HVAC contractor’s licensed electrician as part of the fit-out, wired and inspected to Ontario code. That keeps the electrical certification on the trade that does the work, not on the buyer.

The condensate drain is the small detail that bites inexperienced installers. The RTU’s evaporator coil produces 5 to 15 gallons of condensate per day in Ontario summers. The line runs from the unit underside, through the curb, into the interior, and out to either a floor drain or a small condensate pump that lifts it to an exterior gravity drain. Skipping the P-trap causes the unit to draw air backward through the drain, which fouls the coil. Every install we coordinate uses a 2-inch P-trap with a clean-out cap.

Economizer Hoods, Free Cooling, and Why Most Ontario Buyers Want One

An economizer is a damper assembly on the RTU’s outdoor-air intake that lets the unit pull cool outdoor air directly into the building when outdoor temperature drops below the cooling setpoint. In Ontario, that’s about 2,000 to 3,000 hours per year where economizing replaces mechanical cooling. On a container fit-out it adds to the unit cost. For occupied container offices in any climate zone south of Sudbury, an economizer on a 5-ton or larger RTU is standard practice and usually called out in the contractor’s energy compliance under Ontario’s SB-10 standard. The HVAC contractor’s design drawings will show the economizer; the supplier (us) needs to know about it because the curb opening for an economizer-equipped unit is slightly different than the same model without one.