Modine HD75 Hot Dawg Power-Vented Natural Gas Unit Heater - 75,000 BTU, 115V, Aluminized Steel

Ceiling-Mounted 75,000 BTU Natural Gas Unit Heater For 3-1/2 To 4-Car Garages, Large Workshops, And Commercial Spaces Up To Approximately 1,875 Sq Ft

The Modine HD75 is the mid-range workhorse in the Hot Dawg lineup. At 75,000 BTU input and 61,500 BTU output (82% efficiency), it covers spaces the HD60 cannot reach while costing less to run than the HD100. It shares the same chassis as the HD60 (25 x 26.8 x 18 inches) but delivers 25% more heat output and 17% more airflow.

The HD75 is the first model in the series to offer optional two-stage ignition, which runs at a lower firing rate during mild conditions and ramps to full output in deep cold. At 58 dBA measured at 5 feet, it is actually quieter than the HD60 (59 dBA) despite moving more air. The PSC motor pushes 1,160 CFM with a 48°F temperature rise and throws heat 38 feet from a 14-foot mounting height.

Quick Specs

• BTU Input: 75,000

• BTU Output: 61,500 (82% efficiency)

• Airflow: 1,160 CFM at 70°F

• Supply Voltage: 115V, 1-Phase, 60 Hz

• Vent Size: 3 inch

• Maximum Mounting Height: 14 ft

• Heat Throw: 38 ft at max mounting height

• Sound Level: 58 dBA at 5 ft

• Dimensions: 25 x 26.8 x 18 inches

• Weight: 85 lbs

Key Features

• 75,000 BTU with 1,160 CFM: 25% more BTU and 17% more airflow than the HD60. Heats 3-1/2 to 4-car garages and commercial spaces up to approximately 1,875 sq ft with standard 8-foot ceilings.

• Two-stage ignition available: The HD75 is the first Hot Dawg model to offer two-stage firing. Low-fire runs quieter and uses less fuel in mild weather. High-fire delivers full 75,000 BTU when temperatures drop. HD30, HD45, and HD60 are single-stage only.

• 58 dBA at 5 feet: Quieter than the HD60 (59 dBA) despite 17% more airflow. About the volume of a normal conversation. Comfortable for occupied workshops and commercial spaces.

• PSC motor, 14-foot mounting height, 38-foot throw: The same 1/12 HP permanent split capacitor motor and 14-inch fan as the HD60. Mounts higher (14 ft vs 12 ft) and throws heat farther (38 ft vs 36 ft).

• Power-vented exhaust: Built-in power venter pushes combustion gases outdoors through 3-inch venting. No chimney required. Horizontal or vertical vent runs.

• 10-year heat exchanger warranty: Aluminized steel tubular design standard. 409 stainless steel is available for corrosive environments (greenhouses, wash bays).

• Converts to propane: Ships natural gas. Modine kit #53079 converts to LP for off-grid or rural sites.

• Cold climate rated: Starts reliably down to -40°F. ETL certified for residential, commercial, and industrial use in the US and Canada. CSA-B149.1 compliant.

Modine HD75 Natural Gas Unit Heater Specifications

Available Options

Fuel Type:

• Natural Gas (standard)

• Propane (via conversion kit #53079, or factory-configured)

Ignition Type:

• Single-Stage, Direct Spark Ignition, 100% Shut-Off with Continuous Retry (standard)

• Two-Stage, Direct Spark Ignition, 100% Shut-Off with Continuous Retry (optional). Two-stage is available on the HD75, HD100, and HD125 only.

Heat Exchanger Material:

• Tubular, Aluminized Steel (standard)

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

Performance Overview

The HD75 moves 1,160 CFM through a 14-inch propeller fan with a 48°F temperature rise and 769 FPM outlet velocity. From a 14-foot mounting height, it throws heat 38 feet across the floor. It shares the same chassis and motor as the HD60 but delivers 25% more BTU (75,000 vs 60,000) and moves 17% more air (1,160 vs 990 CFM), while running 1 dBA quieter (58 vs 59 dBA).

Construction and Design

Included Accessories

• 1-inch angle mounting brackets (2), slotted for 16" or 24" joist centers

• Adjustable front-discharge louvers

• Built-in power venter assembly

• Installation and service manual

Not included (sold separately):

• Vent pipe and fittings (3-inch diameter required)

• Thermostat (compatible with any standard 24V thermostat)

• LP conversion kit (Modine #53079, if propane is needed)

• Gas supply piping and shutoff valve

Applications

• 3-1/2 to 4-car garages and large attached garages

• Large workshops, woodworking shops, and fabrication spaces

• Mid-size warehouses and storage buildings

• Greenhouse heating and agricultural outbuildings

• Auto repair bays and multi-bay service stations

• Retail stockrooms and back-of-house commercial areas

• Loading dock areas and maintenance rooms

Installation Tips

The HD75 is a ceiling-mount unit. A few things to keep in mind:

• Same chassis as the HD60. If you are upgrading from an HD60, the HD75 fits the same mounting points (25 x 26.8 x 18 inches). No reframing needed.

• 14-foot max mounting height. The HD75 mounts 2 feet higher than the HD60 (14 ft vs 12 ft). Verify your ceiling height and adjust louver angles accordingly.

• 3-inch vent pipe required. Keep vent runs short and straight. Each 90-degree elbow reduces draft performance. Horizontal runs must slope upward toward the termination point.

• Gas line sizing. The HD75 uses a 1/2-inch gas connection, but the supply line from your meter must deliver 75,000 BTU/hr at the required pressure. Consult a licensed gas fitter for long runs.

• Any standard 24V thermostat works. Mount at breathing height (~5 feet), on an interior wall, away from drafts and windows.

• Clearances: 1 inch top and non-access side. 18 inches on the access side and rear. 4 inches from vent connector. Minimum 7 feet floor clearance (commercial) or 5 feet (residential).

Buy the Modine HD75 Hot Dawg Natural Gas Unit Heater Online from Cleanflow

The HD75 is the mid-range Hot Dawg that bridges the gap between the HD60 and HD100. It shares the HD60's compact chassis but delivers 25% more heat and offers the option of two-stage ignition for fuel savings in milder weather. Cleanflow Utility Supply Company stocks the HD75 Natural Gas Unit Heater 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 and product expertise. 

Not the right fit? Cleanflow offers hassle-free returns and exchanges on all orders.

Frequently Asked Questions

What size space can the Modine HD75 heat?

The HD75 outputs 61,500 BTU (82% efficiency) and handles spaces up to approximately 1,875 sq ft with 8-foot ceilings and moderate insulation. Modine rates it for 3-1/2 to 4-car garages. For larger or poorly insulated spaces, step up to the HD100. Use the Cleanflow BTU Calculator for a specific estimate.

How does the HD75 compare to the HD60?

Same chassis (25 x 26.8 x 18 inches), same 14-inch fan, same PSC motor. The HD75 delivers 25% more BTU (75,000 vs 60,000) and 17% more airflow (1,160 vs 990 CFM). It mounts higher (14 ft vs 12 ft) and throws heat farther (38 ft vs 36 ft). The HD75 is actually 1 dBA quieter (58 vs 59). It also offers optional two-stage ignition, which the HD60 does not.

How does the HD75 compare to the HD100?

The HD100 delivers 33% more BTU (100,000 vs 75,000) and moves 22% more air (1,420 vs 1,160 CFM). Both share the same chassis size. The HD100 mounts up to 16 feet (vs 14) and throws heat 42 feet (vs 38). Choose the HD75 for 3-1/2 to 4-car garages. Choose the HD100 for 4+ car garages and larger commercial spaces.

What does two-stage ignition mean?

Two-stage ignition fires at a lower rate during mild conditions and ramps to full 75,000 BTU output in deep cold. This saves fuel on moderate days, reduces temperature swings, and runs quieter at low-fire. Two-stage is optional on the HD75, HD100, and HD125. The HD30, HD45, and HD60 are single-stage only.

Is the HD75 good for cold climates?

Yes. Rated for startup down to -40°F. The power venter keeps combustion sealed from the space. ETL certified for use in the US and Canada. CSA-B149.1 compliant. Reliable in Canadian and northern US winters.

Can the HD75 run on propane?

Yes. Ships configured for natural gas. Converts to propane using Modine kit #53079, sold separately.

How loud is the Modine HD75?

58 dBA at 5 feet. About the volume of a normal conversation. It is 1 dBA quieter than the HD60 despite moving 17% more air. Comfortable for occupied workshops and commercial spaces.

Does the HD75 come with mounting brackets?

Yes. Includes 1-inch angle brackets that fit 16-inch or 24-inch joist centers. No additional mounting hardware needed.

What ceiling clearance does the HD75 need?

Mounts 1 inch from the ceiling. Keep 18 inches clear on the access side and rear. Non-access side needs 1 inch. Vent connector clearance is 4 inches. Bottom of unit must be at least 7 feet above the floor (commercial) or 5 feet (residential).

What is the warranty?

10 years on the heat exchanger, 2 years on all other parts. Aluminized steel heat exchanger is standard. 409 stainless steel is available for high-corrosion environments.