Modine HD125 Unit Heater

Do you need to keep a large greenhouse, workshop or warehouse warm through winter? Then the Modine HD125 Unit Heater is built for the job. It’s a powerful, gas-fired “Hot Dawg” unit heater with a 125,000 BTU input. Above all, it delivers strong, even, reliable heat for big spaces. So your plants — or your work — stay protected when the temperature drops.

Modine has built quality unit heaters since 1916, and the HD125 carries that reputation. For example, it uses a tough aluminised-steel heat exchanger, backed by a 10-year warranty. In addition, a sealed, permanently-lubricated motor keeps it running dependably for years. So it’s a heating solution you can install once and rely on for the long haul.

Why Choose the Modine HD125

The HD125 combines power, efficiency and smart design. To start, it produces 102,500 BTU of output at 82% thermal efficiency. So you get a lot of usable heat for your fuel. In addition, the propeller fan moves around 1,980 CFM of air and throws heat up to 17 metres (56 ft). As a result, it warms large areas quickly and evenly.

It’s also designed to be easy to live with. For example, the low-profile cabinet mounts close to the ceiling, so it stays out of the way. In addition, it runs quietly, so it won’t disturb your work. Plus, the gas, electrical and flue connections can be reversed simply by flipping the unit. So it suits left- or right-hand installation. Better still, the power-vented exhaust uses small-diameter vent pipe, which keeps installation straightforward for your installer.

H2: Key Features

• Powerful 125,000 BTU input / 102,500 BTU output gas unit heater
• 82% thermal efficiency for economical heating
• Heats large areas — up to ~17m (56 ft) heat throw
• Around 1,980 CFM airflow from the propeller fan
• Low-profile design mounts close to the ceiling
• Quiet operation
• Direct-spark ignition with 100% safety shut-off
• Reversible gas, electrical and flue connections (left or right hand)
• Power-vented exhaust uses small-diameter vent pipe
• Tough aluminised-steel heat exchanger
• 10-year heat-exchanger warranty (2 years parts)

H2: Specifications

• BTU input: 125,000 BTU/hr
• BTU output: 102,500 BTU/hr
• Thermal efficiency: 82%
• Airflow: ~1,980 CFM
• Heat throw: up to ~17m (56 ft)
• Maximum mounting height: ~4.9m (16 ft)
• Ignition: direct spark, single-stage
• Vent size: 4″ (~100mm)
• Heat exchanger: aluminised steel
• Dimensions: approx. 787mm D x 902mm W x 521mm H (31″ x 35.5″ x 20.5″)
• Weight: approx. 58kg (128 lb)
• Warranty: 10-year heat exchanger, 2-year parts
• Note: ceiling mounting brackets sold separately; can run natural gas or (with a conversion kit) propane/LPG

Browse our full greenhouse heating and climate-control range and greenhouse accessories, or speak with our team for help sizing the right heater for your space.

H2: Ideal Applications

The HD125 suits a wide range of large spaces. For example, it’s a popular choice for commercial greenhouses, where steady winter warmth protects crops and extends the growing season. In addition, it’s well suited to workshops, garages, sheds, warehouses and storage facilities. So whether you’re protecting plants or keeping a workspace comfortable, it delivers serious heat. For smaller spaces, a lower-output model may suit better — so talk to our team about sizing.

H2: Installation, Gas and Safety (Australia)

This is the important part, so please read it carefully. The HD125 is a vented gas appliance, so it must be installed by a licensed gasfitter in line with Australian gas-installation requirements. In addition, gas appliances in Australia must meet the relevant Australian Standards and certification. So before you buy, confirm that the unit and its configuration are approved for use and sale in Australia. Please also note the unit’s electrical supply (the standard US model is 115V), and check it suits Australian power, or that you have the correct variant.

For authoritative guidance, the Australian Gas Association / Gas Technical Regulators and your state energy safety regulator (for example, Energy Safe Victoria or NSW Fair Trading) set the rules for gas appliance installation. So always check current requirements before installing. We’re happy to help you confirm the right specification for your project.

H2: Frequently Asked Questions

What size space does the HD125 heat? With 125,000 BTU input and a 17m heat throw, it’s designed for large spaces — commercial greenhouses, big workshops, warehouses and similar. So it’s best for serious heating needs rather than small rooms.

How efficient is it? It runs at 82% thermal efficiency, producing 102,500 BTU of output. So it delivers a lot of usable heat economically.

Can it run on LPG? It’s set up for natural gas, but it can be converted to propane/LPG using the correct conversion kit. So confirm the fuel type for your site.

Does it need professional installation? Yes. As a vented gas appliance, it must be installed by a licensed gasfitter in line with Australian requirements.

What warranty does it come with? A 10-year warranty on the heat exchanger and 2 years on parts.

H2: Conclusion

In the end, the Modine HD125 Unit Heater is a powerful, efficient and dependable way to heat a large greenhouse, workshop or warehouse. It combines strong 125,000 BTU output, a long heat throw, a low-profile design and a 10-year heat-exchanger warranty. Plus, with professional installation, it’ll keep your space warm for years. So browse our heating range or get in touch for expert sizing and supply advice today.