25-Ton Packaged Rooftop Units: Selection Notes for the Largest Size We List
A 25-ton rooftop unit is nominally 300,000 Btu/h of cooling and is the largest tonnage in our Commercial Rooftop Units section. Units of this size serve the biggest single zones on a commercial roof, and they come with the heaviest cabinets, the largest gas inputs and the most demanding electrical circuits on the site. The product mix is focused: Daikin's R-32 DSG gas/electric and DSC cooling-only units, a Rheem R-454B RGEGYB gas/electric unit in 460V, and Daikin DFG R-410A gas/electric listings.
This page focuses on the decisions that are specific to the top of the range: whether 25 tons in one cabinet is the right design, how efficiency compares to smaller sizes, and how to handle the heaviest lift and the biggest utility connections.
Applications and the One-Unit vs. Multiple-Unit Question
Twenty-five-ton packaged units are typically found on very large open spaces: big-box retail and grocery sales floors, arenas and large gymnasiums, convention and banquet spaces, worship centers, and large warehouse or light manufacturing areas that need comfort cooling. At this size, the alternative is usually two or three smaller units, such as two 12.5-ton units or a 15 plus a 10. A single 25-ton unit consolidates the curb, gas and electrical connections into one place. Multiple units spread the risk of a failure, allow zoning across a large floor and keep each lift lighter. Ventilation load is often a big share of the total at this size, so the load calculation, including design outdoor air, should drive the decision. Rules of thumb based on square footage are especially unreliable for large assembly spaces.
Capacity and Efficiency at 25 Tons
The current-production units list 284,000 to 290,000 Btu/h of cooling capacity, and the Daikin DFG lists 300,000 Btu/h. Listed efficiencies here are a step below the smaller sizes on this site:
- Daikin DSC cooling only: 13.2 IEER, 10 EER.
- Daikin DSG gas/electric: 13 IEER, 9 EER.
- Rheem RGEGYB gas/electric: 13 IEER, 9 EER.
- Daikin DFG gas/electric: 13 IEER.
Lower ratings at the largest size are common across packaged equipment, and they are worth factoring into the one-unit versus multiple-unit comparison. Two smaller units from the 12.5 Ton Rooftop Units page, for example, are listed at higher IEER values. Whether that efficiency difference outweighs the added installation cost of a second curb, circuit and gas connection is a site-specific calculation based on run hours and utility rates. If the project must meet a code or incentive minimum, confirm the AHRI-certified rating for the exact model and options.
Electrical Options
Every unit on this page is three-phase. Daikin DSG, DSC and DFG are listed in 208/230V, 460V and 575V. The Rheem RGEGYB at 25 tons is listed in 460V only. A 25-ton unit on 208/230V requires a large circuit, so verify panel capacity and conductor routing early; where 480V service exists, 460V equipment typically reduces current and conductor size considerably. Size the circuit from the MCA and MOP on the product listing, and check measured voltage and phase balance before startup. Large three-phase compressors and blower motors are sensitive to voltage imbalance.
Gas Heat at the Top of the Range
The Daikin DSG listings are offered with 260,000, 360,000 or 400,000 Btu/h gas input, and the Rheem RGEGYB listing shows 400,000 Btu/h input. Note that the maximum input is the same as at 20 tons, while the airflow is higher, so the temperature rise at a given input will be lower. Check the temperature rise range on the product page against your design airflow and the heating load. Confirm gas meter, regulator and piping capacity for the full connected load and the inlet pressure the manufacturer requires. For very cold climates with high ventilation rates, confirm the selected input actually covers the heating load including outdoor air, and talk with the engineer if it does not.
Compressors and Part-Load Behavior
The Daikin listings at 25 tons show two compressors, giving two stages of cooling capacity, and the Rheem RGEGYB listing describes two-stage operation with a belt-drive blower on a VFD. A 25-ton zone spends most hours at part load, so staging and blower control matter for humidity and comfort. For spaces with swinging occupancy, such as arenas or worship centers, discuss demand-controlled ventilation and the control sequence with the engineer.
Heaviest Lift on the Site
Listed weights here run from about 2,130 lb for the Daikin DSC to about 2,320 lb for the Daikin DSG. Plan the lift accordingly:
- Give the crane company the exact weight and dimensions from the product page and installation manual, and the distance from the crane setup to the curb.
- Use spreader bars and the designated lifting points only.
- Have the roof structure reviewed by a structural engineer whenever weight, location or framing differs from the original installation.
- Set and flash the curb before lift day, and stage all connection materials so the unit can be secured and connected without delay.
Curb, Duct and Service Clearances
A 25-ton curb is a significant fabrication. Cross-brand and cross-generation replacements usually need a new curb or a manufacturer-approved adapter curb, and supply and return openings must line up with the existing duct. Confirm downflow or horizontal discharge on the selected model. Check service clearances on all access sides; large cabinets need room to pull compressors, blower assemblies and filters, and parapets or neighboring equipment can block access.
Refrigerant, Economizer and Code Notes
Daikin DSG and DSC use R-32 and Rheem RGEGYB uses R-454B, both A2L refrigerants. These units carry larger charges than smaller packaged equipment, so review the installation manual's A2L section for leak detection and mitigation requirements, use A2L-rated tools and recovery equipment, and keep factory sensors wired as shown. Daikin DFG listings use R-410A; new R-410A packaged equipment is no longer being manufactured for this application, so confirm availability and project acceptance before ordering.
An air-side economizer, economizer fault detection and demand-controlled ventilation may be required at this capacity depending on climate zone, space type and the adopted edition of ASHRAE 90.1 or IECC. Confirm with the engineer of record and order the economizer and relief option designed for the cabinet.
Availability
Units at the top of the range move in lower volume, and 575V and 460V-only versions in particular may not be stocked locally. Confirm availability and lead time before committing to a crane date or a building opening, and order the curb at the same time. If schedule is critical, compare options on the 20 Ton Rooftop Units page or a multi-unit design.
25-Ton Models in This Category
| Brand | Series | Type | Voltages Listed | Efficiency (as listed) |
|---|
| Daikin | DSC | Cooling only, R-32 | 208/230V-3, 460V-3, 575V-3 | 13.2 IEER, 10 EER |
| Daikin | DSG | Gas/electric, R-32, 260,000 to 400,000 Btu/h input | 208/230V-3, 460V-3, 575V-3 | 13 IEER, 9 EER |
| Daikin | DFG | Gas/electric, R-410A | 208/230V-3, 460V-3, 575V-3 | 13 IEER |
| Rheem | RGEGYB | Gas/electric, R-454B, 400,000 Btu/h input, belt drive VFD | 460V-3 | 13 IEER, 9 EER |
Figures are from the product listings. Confirm against the manufacturer's spec sheet or AHRI certificate for the exact model number before submitting.
Frequently Asked Questions
Why are 25-ton units rated lower in IEER than smaller sizes?
Efficiency targets and achievable ratings generally decrease as packaged equipment gets larger. On this site, the 25-ton units are listed at about 13 IEER, while the 12.5-ton units range from 14 to 16 IEER.
Is there a 25-ton cooling-only unit?
Yes. The Daikin DSC is listed at 25 tons in 208/230V, 460V and 575V, at 13.2 IEER.
Can I get a Rheem 25-ton unit in 208/230V?
The Rheem RGEGYB on this page is listed in 460V only. For 208/230V at 25 tons, the Daikin DSG and DSC listings include 208/230V.
What is the largest gas heat input at 25 tons?
400,000 Btu/h, offered on Daikin DSG and listed on Rheem RGEGYB. Daikin DSG is also offered at 260,000 and 360,000 Btu/h.
Should I replace one 25-ton unit with two smaller units?
It can make sense for redundancy, zoning and lighter lifts, and smaller units here carry higher listed IEER. It also adds curbs, circuits and gas connections. Compare total installed cost and operating cost for the specific building.
How much clearance does a 25-ton unit need for service?
Service and airflow clearances are model-specific. Check the installation manual for the exact unit and leave room to remove compressors, blower assemblies and filters.
