132 Cartwright Ave, North York ON
Mon–Sat 8am–7pm · Sun 9am–5pm
Commercial rooftop units · 3–6 ton
3, 4, 5 & 6 ton rooftop units
for small commercial buildings
Choosing the right RTU tonnage is the difference between comfortable tenants and endless complaints. This guide explains how 3, 4, 5, and 6 ton packaged rooftop units fit Toronto & GTA retail, offices, clinics, and light commercial spaces — and how Toronto Air Systems sizes and installs them from our North York shop.
Commercial RTU sizing
Why tonnage matters for Toronto small commercial
A rooftop unit is not a residential furnace with a different paint job. Packaged RTUs combine heating, cooling, and often economizer or ventilation functions in one curb-mounted cabinet. For small commercial buildings across Toronto and the GTA, the sweet spot is often 3, 4, 5, or 6 tons — roughly 36,000 to 72,000 BTU/h of cooling capacity — but the right choice depends on square footage, occupancy, glazing, kitchen loads, and how the space is used hour by hour.
Undersize and you get hot afternoons, iced coils, and short-cycling compressors. Oversize and you get humidity problems, drafts, and higher first cost. We load-calculate for real GTA design temperatures and building use — then match curb, gas, electrical, and condensate paths. Explore our commercial HVAC Toronto hub for broader rooftop and facility services.
Whether you run a strip-plaza storefront in Scarborough, a clinic in Mississauga, or a second-floor office in North York, this guide walks through what each tonnage typically supports and when to step up or down. Call 647 953-4252 if you already have model numbers or a failing unit and need a replacement path.
Toronto and GTA conditions are not mild-climate marketing charts. Design temperatures, humidity, older building stock, and mixed fuel strategies change how commercial rooftop units should be specified. We start with how you use the space — occupancy, hours, duct capacity, electrical service, and existing equipment — before recommending parts or a full replacement.
Homeowners, landlords, and facility managers call us when systems short-cycle, ice up, leave rooms uneven, spike utility bills, or fail on the first deep freeze or heat wave. Whether you need a same-week repair or a planned upgrade, we document findings and present repair-versus-replace paths with pricing you can compare.
Explore related hubs for heating, cooling, and commercial HVAC, or ask about rebates and incentives that may apply to high-efficiency equipment. Call 647 953-4252 with model numbers and symptoms so we arrive prepared.
What matters most for commercial rooftop units in the GTA
Right sizing, licensed gas/refrigeration work, and commissioning beat the cheapest sticker price. We verify airflow, safety devices, condensate paths, and controls so your system does not fail the first extreme week of the season. Ask us about dual-fuel, zoning, and rebate-eligible models during your quote.
High-efficiency commercial equipment incentives
Qualifying high-efficiency rooftop replacements may unlock utility or provincial incentives depending on SEER2/IEER and gas furnace AFUE. We flag likely programs on your quote — see our HVAC rebates & incentives page for current GTA context.
Before you pick a 3–6 ton RTU
- Conditioned floor area and ceiling height of each zone
- Peak occupancy and hours of operation (retail vs office vs clinic)
- South/west glass load and solar gain in summer
- Kitchen, server, or process heat that the RTU must offset
- Existing curb size, gas line capacity, and electrical disconnect
- Fresh-air / economizer requirements for Ontario code and comfort
- Noise limits for neighbours or rooftop tenants below
- Age and failure mode of the current packaged unit
Practical sequence
How we approach commercial rooftop units
A structured process so you always know the next step.
01
Consult
Goals & constraints
02
Assess
On-site measurements
03
Compare
Repair vs replace
04
Schedule
Parts & access
05
Execute
Licensed install
06
Verify
Commission & teach
Where this fits
Common commercial rooftop units applications in Toronto & the GTA
Different buildings need different equipment paths. These are the scenarios we see most often.
01
Detached & semi-detached homes
Full replacements, dual-fuel strategies, and comfort fixes for older duct systems common across Toronto neighbourhoods.
02
Condos & townhomes
Compact footprints, quiet operation, and board-friendly installs where access and condensate matter.
03
Additions & renovations
Matching new loads without oversizing, including ductless zones where trunks cannot reach.
04
Light commercial
Retail, clinics, offices, and mixed-use spaces that need documented maintenance and predictable uptime.
05
Rental properties
Durable equipment choices, clear landlord options, and service plans that reduce emergency callouts.
06
Efficiency upgrades
High-AFUE / SEER2 / heat-pump paths with rebate paperwork guidance when programs apply.
Step by step
From site survey to a running rooftop
From first call to commissioned equipment, you always know the next step, the timeline, and what is included.
01
Consultation
Tell us about your home or building, symptoms, and goals — by phone or online form.
02
On-site assessment
A licensed technician evaluates your existing rooftop unit, ductwork, and load requirements.
03
Written quote
You receive clear options, pricing, timelines, and rebate notes — no vague estimates.
04
Installation or repair
Our TSSA-licensed team completes the work to code with minimal disruption.
05
Follow-up support
We walk you through operation, warranty, and ongoing maintenance recommendations.
How we help
Rooftop unit services for small commercial in the GTA
From tonnage advice to curb-ready installs — licensed crews, documented options, and commissioning that matches how your building actually runs.
Load calc & tonnage selection
Manual J-style commercial load review for 3–6 ton candidates — occupancy, envelope, and internal gains included.
Commercial HVAC Toronto →RTU replacement
Like-for-like or right-sized upgrades with curb adapters, gas, electrical, condensate, and control reconnect.
New package installs
New construction and renovations: curb coordination, duct transitions, and thermostat or BMS interfaces.
Repair & diagnostics
Compressor, economizer, ignition, blower, and refrigerant faults diagnosed before you commit to replace.
Seasonal maintenance
Filter, coil, belt, gas train, and safety checks timed before peak summer and winter loads.
Multi-unit plaza support
Coordinated service across strip plazas and mixed-use roofs with clear reporting for property managers.
Request a commercial quote →Related services
Sizing your rooftop unit? Start here.
This guide pairs with our full commercial HVAC service line.
01
Commercial HVAC Toronto
Rooftop install, repair & maintenance for GTA commercial buildings.
View commercial HVAC →02
Rebates & incentives
Check current programs before you order high-efficiency equipment.
See rebates →FAQ
3–6 ton rooftop FAQ — Toronto & GTA
How many square feet does a 5 ton rooftop unit cool?
Rules of thumb (about 400–600 sq ft per ton) are only starting points. Occupancy, glass, kitchen equipment, and ventilation often push a “5-ton looking” space toward 6 tons — or allow a well-insulated office to stay at 4. We load-calculate instead of guessing from floor area alone.
What is the difference between a 3 ton and 4 ton RTU?
About 12,000 BTU/h of cooling capacity, plus typically larger blowers, electrical requirements, and curb/weight implications. Stepping up a ton only helps if the load calculation supports it; oversized units can short-cycle and leave humidity high.
Can I put a 6 ton unit on a curb built for 4 tons?
Sometimes with a curb adapter and structural review — sometimes not. Footprint, supply/return openings, weight, and gas/electrical capacity all matter. We measure the existing curb before ordering equipment.
Do small commercial RTUs include heating in Toronto?
Most packaged gas/electric RTUs for the GTA include a gas heat section sized for winter design loads, plus cooling for summer. Electric heat or heat-pump packaged options exist for specific sites — we recommend based on fuel availability and operating cost.
How long does a commercial rooftop replacement take?
Many like-for-like 3–6 ton swaps are same-day or overnight once equipment and curb adapters are on site. Complex duct transitions, gas upsizing, or crane windows can add time. We schedule around your business hours when possible.
Should I repair or replace my aging 4 ton rooftop?
If the cabinet, heat exchanger, and coils are sound and the fault is a single component, repair can win. Repeated compressor failures, rusted heat exchangers, obsolete controls, or chronic undersizing usually favour replacement. We present both paths with numbers.
How do I get a rooftop tonnage assessment in the GTA?
Call 647 953-4252 or use our contact form. Share floor plans or photos of the roof curb if you have them — we will propose 3–6 ton options with a written quote.
How much does commercial rooftop units cost in Toronto?
Cost depends on equipment capacity, brand, duct or piping complexity, electrical/gas upgrades, and whether you repair or replace. We provide written quotes after a site assessment so you can compare options fairly. Call 647 953-4252 for a visit.
Do you serve my area in the GTA?
Yes. We are based in North York at 132 Cartwright Ave and regularly serve Toronto, Mississauga, Vaughan, Markham, Scarborough, Etobicoke, Brampton, and nearby communities.
Are your technicians licensed?
Yes. Gas and refrigeration work is performed by TSSA-licensed technicians. We follow Ontario code practice for venting, refrigerant handling, electrical disconnects, and condensate management.
Ready to size the right 3–6 ton rooftop?
Book a commercial assessment with Toronto Air Systems — clear tonnage advice and written pricing. Call 647 953-4252.