Carrier WeatherMaster 48QE Large Commercial Hybrid Heat Rooftop Unit – Supplied & Professionally Installed by 4Most Energy
The WeatherMaster 48QE is a single-package hybrid heat rooftop unit that pairs a two-stage heat pump with gas heat backup, sized 15 to 25 nominal tons for large commercial, institutional, and light-industrial buildings. Twin tandem scroll compressors run on Puron Advance (R-454B) refrigerant — GWP of 466, a 75% reduction from legacy R-410A — delivering up to 17.0 IEER and 11.40 EER in cooling, with heat pump heating rated at a 3.50 COP at 47°F ambient and down to 2.20 COP at 17°F ambient before the stainless steel heat exchanger provides gas backup. Gas heat is available in low, medium, and high input configurations up to 400/324 MBH input/output, with an integrated gas controller (IGC), direct-spark ignition, and a redundant main gas valve delivering 81% thermal efficiency. Because R-454B is a mildly flammable A2L refrigerant, every unit ships with a factory-installed refrigerant leak dissipation system — a dedicated control board and UL-certified sensor that automatically detects and dissipates a leak with no field wiring required. All 48QE units meet DOE 2023 and ASHRAE 90.1 minimum efficiency requirements, are AHRI 340/360 certified, and are UL listed to ANSI Z21.47 and UL 60335-2-40.
Rated performance depends entirely on correct field installation. Ontario installations of a unit this size require licensed TSSA gas technician sizing of the gas line and meter for backup heat, combustion and gas-train testing at start-up, and induced-draft venting configured per the unit’s discharge orientation. Roof curb selection (14 in. or 24 in.), structural load review for base unit weights up to roughly 2,545 lb, electrical service sized to the unit’s voltage (208/230-460/575V, 3-phase) and combined heat pump/gas MCA/MOCP rating, and ESA-compliant thru-the-base electrical connections are equally code-driven. 4Most Energy is a certified installer for commercial rooftop unit installation Toronto, packaged rooftop replacement GTA, and Carrier WeatherMaster 48QE installation Ontario projects, providing licensed gas technician near me-level combustion testing and A2L refrigerant commissioning, and ENERGY STAR–calibre hybrid heat rooftop Toronto service standards on every job — so the IEER, heating COP, and rated cooling capacity on the nameplate are what the building actually gets.
Replacement Option
The WeatherMaster 48QE is designed to fit on existing roof curbs, making it straightforward for 4Most Energy to replace aging Trane, Lennox, York (Johnson Controls), Daikin, Rheem, and AAON gas or heat pump packaged rooftop units of comparable tonnage using an appropriately sized curb adapter to bridge differing roof curb and duct footprints. This lets 4Most Energy convert a building from a straight gas or straight electric rooftop unit to hybrid heat pump/gas operation from any of these manufacturers without necessarily requiring a full roof curb and structural rework, minimizing both project cost and rooftop downtime.
Warranty
Carrier backs the WeatherMaster 48QE with a 3-year limited parts warranty from the factory. 4Most Energy handles warranty registration and start-up documentation
on your behalf.
Why Install the Carrier WeatherMaster 48QE with 4Most Energy?
- Puron Advance (R-454B) refrigerant — GWP of 466, a 75% reduction from legacy R-410A, with a factory-installed A2L refrigerant leak dissipation system standard on every unit for automatic leak detection and mitigation.
- Hybrid Heat pairing — a two-stage heat pump as the primary heat source, backed by gas heat that engages automatically when mechanical heating can no longer efficiently meet the load, for a more sustainable heat source than electric strip heat.
- EcoBlue vane axial indoor fan system — direct-drive ECM motor, 75% fewer moving parts than belt-drive designs, up to 40% better efficiency, and slow ramp-up for quieter, more reliable operation.
- Tandem scroll compressors on a single refrigeration circuit, with a fully active evaporator coil and internal line-break overload protection.
- SystemVu intelligent controller (standard) — large multi-line display, USB data port, and built-in i-Vu, CCN, and BACnet compatibility, meeting California Title 24 Fault Detection and Diagnostic (FDD) requirements.
- Optional Humidi-MiZer adaptive dehumidification system — sub-cooling and hot gas reheat modes for improved part-load humidity control, includes low ambient controller.
- Optional low ambient controller — extends cooling operation down to -20°F ambient.
- Single point gas and electrical connections for simplified rooftop wiring and piping, with thru-the-base capability standard.
- Tool-less filter access door and hinged access panels throughout for faster service and field repairs.
- “Replacement original” fit design — lighter units and dedicated vertical or horizontal airflow configurations engineered to land on existing roof curbs, easing gas-to-hybrid or heat-pump-to-hybrid conversions.
Carrier 48QE Series Specifications
| Model | Nominal Tons | Net Cooling (MBH) |
EER | IEER (2-speed) |
Rated CFM | Sound (dBA, A-wtd) |
Base Unit Weight (lb) |
|---|---|---|---|---|---|---|---|
| 48QE**17 | 15.0 | 174.0 | 11.40 | 17.0 | 6,000 | 84.1 | 1,990 |
| 48QE**24 | 20.0 | 230.0 | 10.40 | 16.2 | 8,000 | 85.9 | 2,382 |
| 48QE**28 | 25.0 | 290.0 | 9.85 | 15.3 | 9,500 | 85.9 | 2,445 |
* Vertical units, standard controls (48QEM/X). All AHRI ratings per Standards 340/360.
Ratings per AHRI Standards 340/360 at 80°F/67°F wb indoor, 95°F db outdoor (cooling).
Horizontal-airflow units carry slightly lower ratings on sizes 24/28 (228.0/286.0 MBH net cooling; 21.9/9.65 EER; 15.7/14.7 IEER) — confirm airflow orientation before quoting. Units with Humidi-MiZer (N/Y models) add approximately 90–100 lb.
Heat Pump Heating Performance (Btu/hr, net)
| Performance Metric | 48QE**17 | 48QE**24 | 48QE**28 |
|---|---|---|---|
| Low Temp. Net Heating @ 17°F amb. (BTU/h) |
96,000 | 134,000 | 172,000 |
| Low Temp. COP | 2.30 | 2.25 | 2.20 |
| High Temp. Net Heating @ 47°F amb. (BTU/h) |
166,000 | 232,000 | 300,000 |
| High Temp. COP | 3.50 | 3.40 | 3.40 |
Standard controls permit compressor cooling operation down to 40°F ambient and heat pump heating operation down to -10°F ambient; an optional low ambient controller extends cooling operation to -20°F. Below the heat pump’s effective heating range, the gas heat exchanger provides backup heat.
Gas Backup Heat Specifications
| Stage | Input / Output (MBH) |
Temp. Rise °F (48QE**17) |
Temp. Rise °F (48QE**24) |
Temp. Rise °F (48QE**28) |
|---|---|---|---|---|
| Low | 176 / 142 | 20–45 | 15–45 | 10–45 |
| Medium | 248 / 200 | 30–55 | 20–55 | 15–55 |
| High | 320 / 260 | 35–60 | 30–60 | 20–60 |
* Natural Gas and Propane, AL/SS Heat Exchanger.
Thermal efficiency 81% across all stages and sizes. Natural gas and propane input/output identical; propane requires a field-installed conversion kit.
The 48QE 17-28 line is sized first by cooling load (15–25 nominal tons) using a proper commercial load calculation — not by matching the tonnage of the unit being replaced, since older rooftop units on the same curb were frequently oversized by the standards of their era. Because the heat pump is the primary heat source, sizing should also weigh the building’s design heating load against the unit’s heat pump output at 17°F and 47°F ambient (see the Heat Pump Heating Performance table) to confirm gas backup engagement frequency will be reasonable for the climate zone, and whether the optional low ambient controller (extending operation to -20°F) is warranted for the site.
Sound-sensitive sites should note that the 24 and 28 sizes rate louder (85.9 dBA) than the 17 size (84.1 dBA). Vertical and horizontal airflow configurations are factory-set and not field-convertible, so confirming ductwork orientation before ordering is essential. 4Most Energy performs load calculation, gas and electrical capacity verification, and roof structural review as part of every quote before ordering.
Installation & Commissioning Steps
| Step | Phase | Description & Core Requirements |
|---|---|---|
| Step 01 | Site Assessment | Existing unit and curb inspection, gas service and meter capacity check, electrical service review, and roof structural/access evaluation for a unit weighing up to roughly 2,545 lb. |
| Step 02 | Load Calculation & Sizing | Confirm correct tonnage, gas backup heat level, low ambient controller need, airflow configuration (vertical or horizontal), and controller setup (SystemVu™ standard). |
| Step 03 | Rigging & Crane Setup | Base rail rigging holes and lifting handles simplify crane placement of the unit onto the existing or new roof curb. |
| Step 04 | Roof Curb & Structural Prep | Install or verify 14 in./24 in. roof curb, full-perimeter seal, and structural support for the unit’s operating weight. |
| Step 05 | Gas Line & Venting Connection | Licensed TSSA gas technician sizes and connects the gas line for backup heat, verifies supply pressure, and configures induced-draft venting for the unit’s discharge orientation. |
| Step 06 | Electrical Connection | ESA-compliant hookup to the building’s disconnect, sized to the unit’s voltage, phase, and combined heat pump/gas MCA/MOCP rating, with thru-the-base connections as specified. |
| Step 07 | Ductwork Tie-in | Supply and return duct connection with turning vanes and sealed transitions. |
| Step 08 | Commissioning | Refrigerant charge verification, A2L leak dissipation system self-test, combustion analysis and gas train test, heat pump/gas changeover setpoint configuration, and airflow confirmation, with warranty registration filed. |
| Step 09 | Final Walkthrough | Filter access, service clearances, and SystemVu™ controller operation demonstrated before the crew leaves site. |
Carrier’s standard coverage on the WeatherMaster 48QE is a 3-year limited parts warranty from the factory. 4Most Energy completes and files the required start-up and combustion test documentation to keep warranty coverage valid.
Routine maintenance is straightforward by design: the EcoBlue direct-drive fan requires no belts, pulleys, or shaft bearings to inspect or replace, and the tool-less filter door simplifies the most frequent service task. Carrier recommends annual combustion testing and gas train inspection, refrigerant leak dissipation system self-test verification, condenser coil cleaning, and condensate drain pan/trap inspection. 4Most Energy offers scheduled maintenance plans covering filter changes, combustion analysis, refrigerant circuit and A2L leak sensor checks, and control board diagnostics via the unit’s built-in LED status indicators and SystemVu display.
Service Area
Greater Toronto Area (GTA) and surrounding regions
Toronto, Markham, Richmond Hill, Vaughan, Aurora, Newmarket, Scarborough, Brampton, and Mississauga.
Extended Service Area: Stouffville, Oshawa, Barrie, Orangeville, Hamilton, St. Catharines, Guelph, Kitchener.
Frequently Asked Questions
How is the 15–25 ton 48QE different from Carrier’s smaller 48QE hybrid units?
All 48QE models share the same Hybrid Heat pairing of heat pump plus gas backup and Puron AdvanceTM (R-454B) refrigerant, but this 15–25 ton line is built for the largest commercial and institutional spaces in the WeatherMaster range, with gas input capacity up to 400 MBH and heat pump heating capacity up to 300,000 Btu/hr, at the tradeoff of a higher standard sound rating (84–86 dBA) than the smaller tonnage lines.
Is R-454B refrigerant safe to use in an occupied building?
Yes — R-454B is a mildly flammable (A2L) refrigerant with a GWP of 466, and Carrier equips every 48QE with a factory-installed, UL-certified refrigerant leak dissipation system that automatically detects and mitigates a leak without field wiring. It must be installed and serviced by a licensed refrigeration mechanic, which 4Most Energy provides on every job.
Is the 48QE a direct replacement for our existing rooftop unit?
In most cases the unit’s “replacement original” fit design lands on existing roof curbs and many competitor curbs without modification, though 4Most Energy always verifies curb dimensions, gas/electrical connection points, and structural load before ordering.
How cold can it get before the 48QE stops running on the heat pump alone?
Standard controls permit compressor cooling operation down to 40°F ambient and rate heating performance at 17°F and 47°F ambient; heat pump heating operation is supported down to -10°F ambient, and an optional low ambient controller extends cooling operation to -20°F. Below the heat pump’s effective range, gas backup takes over automatically.
Does the 48QE qualify for any Ontario commercial efficiency incentives?
should be confirmed for the specific building type and size before quoting, as most current
