Modine HD125 Hot Dawg Power-Vented Natural Gas Unit Heater - 125,000 BTU, 115V, Aluminized Steel

The Largest Hot Dawg: 125,000 BTU Ceiling-Mounted Natural Gas Unit Heater For Large Garages, Workshops, Warehouses, And Commercial Spaces

The Modine HD125 (HD125AS0111FDAN) is the most powerful unit in the Hot Dawg HD lineup. At 125,000 BTU input and 102,500 BTU output (82% efficiency), it delivers 25% more heating capacity than the HD100 while sharing the same large chassis (31 x 35.5 x 20.5 inches) and 4-inch venting. It pushes 1,980 CFM with a 47°F temperature rise and throws heat 56 feet from a maximum mounting height of 16 feet.

If you are already considering the HD100 and need more capacity in the same footprint, the HD125 is the direct step up. Same chassis, same 4-inch vent pipe, same mounting points. The HD125 adds 33% more airflow (1,980 vs 1,490 CFM), a longer heat throw (56 vs 42 feet), and a higher maximum mounting height (16 vs 12 feet). It uses a totally enclosed fan motor standard on the 100 and 125 models for added durability in dusty environments.

Quick Specs

• BTU Input: 125,000
• BTU Output: 102,500 (82% efficiency)
• Airflow: 1,980 CFM at 70°F
• Supply Voltage: 115V, 1-Phase, 60 Hz
• Vent Size: 4 inch
• Maximum Mounting Height: 16 ft
• Heat Throw: 56 ft at max mounting height
• Dimensions: 31 x 35.5 x 20.5 inches
• Weight: 128 lbs

Key Features

• 125,000 BTU with 1,980 CFM: The highest output and airflow in the Hot Dawg HD series. 25% more BTU and 33% more airflow than the HD100. Heats large garages, multi-bay shops, warehouses, and commercial spaces.
• 56-foot heat throw from 16 feet: The longest throw and highest mounting height in the HD lineup. The HD100 reaches 42 feet from 12 feet. The HD125 covers significantly more floor area from a higher ceiling.
• Same chassis as HD100: Both use the 31 x 35.5 x 20.5-inch frame and 4-inch vent pipe. If you already have an HD100 installed, the HD125 fits the same mounting points and vent run.
• Two-stage ignition available: Low-fire runs quieter and uses less fuel on moderate days. High-fire delivers full 125,000 BTU in deep cold. Available on HD75, HD100, and HD125.
• Totally enclosed fan motor: Standard on the HD100 and HD125. Sealed motor housing protects against dust, debris, and moisture for longer motor life in shop and industrial environments.
• Power-vented exhaust: Built-in power venter pushes combustion gases outdoors through 4-inch venting. No chimney required. Side-wall or roof venting.
• 10-year heat exchanger warranty: Aluminized steel tubular design standard. 409 stainless steel available for greenhouses and corrosive environments.
• Converts to propane: Ships natural gas. Modine kit #53081 converts to LP. Note: the HD125 uses a different LP kit than the HD100 (#53080). Do not interchange.
• Cold climate rated: Starts reliably down to -40°F. ETL certified for residential, commercial, and industrial use in the US and Canada.

Modine HD125 Natural Gas Unit Heater Specifications

Available Options

Fuel Type:

• Natural Gas (standard)
• Propane (via conversion kit #53081, or factory-configured)

Ignition Type:

• Single-Stage, Direct Spark Ignition, 100% Shut-Off with Continuous Retry (standard)
• Two-Stage, Direct Spark Ignition (optional). Available on HD75, HD100, and HD125 only.

Heat Exchanger Material:

• Tubular, Aluminized Steel (standard)
• Tubular, 409 Stainless Steel (optional, for high-corrosion environments)

Performance Overview

The HD125 pushes 1,980 CFM at a 47°F temperature rise, delivering 102,500 BTU output. From its 16-foot maximum mounting height, it throws heat 56 feet. Compared to the HD100, the HD125 delivers 25% more BTU (125,000 vs 100,000), 33% more airflow (1,980 vs 1,490 CFM), and reaches 33% farther (56 vs 42 feet). Its 16-foot mounting height also exceeds the HD100 (12 feet), making it suitable for taller commercial and industrial ceilings. The lower temperature rise (47°F vs 50°F on the HD100) reflects the higher air volume moving through the same chassis.

Included Accessories

• Adjustable front-discharge louvers
• Built-in power venter assembly
• Finger-proof fan guard
• Installation and service manual

Not included (sold separately):

• Mounting brackets (accessory on HD100 and HD125, included on HD30-HD75)
• Vent pipe and fittings (4-inch diameter required)
• Thermostat (any standard 24V thermostat)
• LP conversion kit (Modine #53081)
• Gas supply piping and shutoff valve

Applications

• Large garages (4+ car) and detached workshops
• Warehouses and distribution centers
• Auto repair shops, multi-bay service stations, and dealership service departments
• Agricultural buildings and large greenhouses
• Retail stockrooms and commercial back-of-house areas
• Loading docks, maintenance bays, and industrial work areas
• Fire stations, equipment storage, and municipal buildings

Installation Tips

• Mounting brackets sold separately. Unlike the HD30 through HD75, the HD125 does not include angle brackets. Order the bracket kit as an accessory.
• 4-inch vent pipe required. Same as the HD100. If replacing an HD75 or smaller, the existing 3-inch vent pipe will not work. Plan for 4-inch vent materials.
• 16-foot max mounting height. Higher than the HD100 (12 ft) and HD75 (14 ft). Confirm your intended mount height and that your ceiling structure can support 128 lbs plus the bracket kit.
• LP kit is model-specific. The HD125 uses Modine #53081, not #53080 (HD100) or #53079 (HD30-HD75). Do not interchange.
• Same chassis as HD100. If upgrading from an HD100, the HD125 fits the same mounting points and vent run. No reframing needed.
• Clearances: 1 inch top and non-access side. 18 inches on access side and rear. 4 inches from vent connector.

Buy the Modine HD125 Hot Dawg Natural Gas Unit Heater Online from Cleanflow

The HD125 is the top of the Hot Dawg HD lineup and the most powerful 125,000 BTU garage heater in the series. It handles the largest residential and mid-size commercial spaces that the HD100 cannot fully reach, and it does so from a higher mounting point with a longer heat throw. 

Cleanflow stocks the HD125 with free shipping on orders over $199 CAD across Canada and the USA. As an authorized Modine supplier, Cleanflow backs every unit with manufacturer warranty support. Not the right fit? Cleanflow offers hassle-free returns and exchanges on all orders.

Frequently Asked Questions

How does the HD125 compare to the HD100?

The HD125 delivers 25% more BTU (125,000 vs 100,000) and 33% more airflow (1,980 vs 1,490 CFM). It throws heat 56 feet from 16 feet, compared to the HD100's 42 feet from 12 feet. Both share the same chassis (31 x 35.5 x 20.5 inches) and 4-inch venting. If you already have an HD100 installed, the HD125 fits the same mounting points and vent pipe. The HD125 uses LP kit #53081 (not the HD100's #53080).

What vent size does the HD125 require?

4-inch diameter, same as the HD100. If replacing an HD75 or smaller model, the existing 3-inch vent pipe will not work.

Can the HD125 run on propane?

Yes. Ships natural gas. Converts to propane with Modine kit #53081. This kit is specific to the HD125. Do not use kits from other models.

Does the HD125 include mounting brackets?

No. Mounting brackets are included on the HD30 through HD75 but sold separately for the HD100 and HD125. Order the bracket kit as an accessory when purchasing.

Is the HD125 good for cold climates like Canada?

Yes. Rated for startup down to -40°F. ETL certified for residential, commercial, and industrial use in the US and Canada. CSA-B149.1 compliant. At 125,000 BTU input (102,500 BTU output), it handles large, poorly insulated, or high-ceiling spaces in extreme cold.