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Packaged RTU vs split system: which to spec for the job
A packaged RTU ships as one factory-charged cabinet on a curb; a split system is field-brazed and evacuated on site.
Short answer
Pick a packaged RTU when you have the roof structure and want one factory-charged cabinet with fewer field connections; pick a split system when the equipment has to go where a packaged unit cannot sit or the roof will not carry it. The single biggest deciding factor is the refrigerant circuit: an RTU arrives sealed and charged from the plant so startup verifies the factory circuit, while a split system is a field-built circuit you braze, pressure test, evacuate, and charge yourself, which raises both the skill and the risk on site.
Packaged RTU vs Split system: side by side
| Factor | Packaged RTU | Split system |
|---|---|---|
| Configuration | One cabinet holding cooling, heat, blowers, filters, and often an economizer, set on a roof curb | Split into an outdoor condenser and an indoor coil or air handler, joined by a lineset and control wiring |
| Refrigerant circuit | Factory-sealed and factory-charged; startup proves the circuit, no field brazing | Field-built: braze the lineset under flowing nitrogen, pressure test, then evacuate to about 500 microns |
| Charging at startup | Verify the factory charge by subcooling (TXV) or superheat (fixed orifice) | Weigh in factory charge plus a per-foot lineset adder beyond the rated length, then verify by subcool/superheat |
| Install skill and steps | Fewer field connections: duct, power, gas; rigging and curb work dominate | More skilled circuit work: brazing, evacuation, decay test, weigh-in; more ways to get it wrong |
| Siting and structure | Needs a level, watertight roof curb and structure rated to carry unit plus curb, snow, and live load | Condenser sits on a level pad with clearance and a wind tie-down; indoor coil placed separately |
| Rigging | Crane pick to lift points with a spreader bar; heavy, one controlled set onto the gasket | No crane for the condenser; ground-set unit, lineset routed to the indoor coil |
| Startup focus | Curb seal, condensate trap, shipping bolts, 3-phase rotation, charge, airflow/ESP, gas temp rise | Airflow first, then charge, split, amps; heat pump adds defrost and aux/emergency heat checks |
| Efficiency rating | AHRI-rated packaged unit; SEER2 and IEER (part-load) held by correct charge and airflow | AHRI-rated matched pair; mismatched coil kills the rating, efficiency, and warranty |
| Best use / size | Light commercial, roughly 3 to 25 tons, single-zone or VAV where roof and structure suit it | Most common residential and light-commercial, including long-line and high-lift where a curb is not an option |
Which should you pick?
Choose Packaged RTU when
- The roof and structure can carry the unit and you want one cabinet with duct, power, and gas as the only field ties
- You want a factory-sealed, factory-charged circuit so startup verifies rather than builds the refrigerant loop
- It is a light commercial single-zone or VAV load in the roughly 3 to 25 ton range with an economizer
- You want gas heat, electric, or heat pump plus economizer packaged in one commissioned assembly
Choose Split system when
- The equipment cannot sit on a curb or the roof will not carry a packaged unit, so indoor and outdoor split makes sense
- The application is residential or light commercial, including long-line and high-lift runs with oil traps
- You have the skill to braze under nitrogen, pull a deep vacuum, and weigh in the charge in the field
- You can confirm a matched AHRI pair to hold the rating, efficiency, and full parts warranty
Bottom line
It depends on where the equipment can physically go and what the structure will carry. If the roof is rated and you want the fewest field connections and a factory-charged circuit, the packaged RTU wins on install simplicity and a startup that verifies instead of builds. If a curb is not practical, the roof is light, or the layout demands separated indoor and outdoor equipment, the split system is the answer, but it moves the refrigerant circuit into the field, so the brazing, evacuation, and charge become yours to get right. Either way the manufacturer's instructions govern every setpoint, and a startup with no recorded readings is not a startup on either machine.
FAQ
What is the main difference between a packaged RTU and a split system?
An RTU is a packaged unit with cooling, heating, fans, and often an economizer in one cabinet on a roof curb, with the refrigerant circuit sealed and charged at the factory. A split system separates the outdoor condenser from the indoor coil and joins them with a lineset you braze, pressure test, evacuate, and charge in the field. The RTU concentrates the work in the curb and rigging; the split moves the refrigerant circuit onto the job site.
Which is faster and lower-risk to install?
A packaged RTU has fewer field connections, duct, power, and gas, and no field brazing, because the circuit ships sealed and charged, so startup verifies the factory circuit rather than building one. A split system adds brazing under nitrogen, a pressure test, a deep vacuum to about 500 microns, and weighing in the charge plus a per-foot lineset adder, which takes more skill and has more failure points. The trade-off is that the RTU needs a level, watertight curb and a roof rated to carry it.
Do both need the same startup and charge checks?
Both verify charge by subcooling on a TXV system and superheat on a fixed-orifice system, set airflow against external static pressure before trusting the charge, and check three-phase scroll rotation. The RTU adds curb seal, condensate trap, shipping-bolt removal, and gas temperature rise; the split adds a field vacuum and decay test, the lineset charge adder, and on a heat pump the defrost and auxiliary heat modes. Record every reading against its target on either machine.