Modine HD45 Unit Heater

Do you need reliable warmth for a smaller greenhouse, garage or workshop? Then the Modine HD45 Unit Heater is the right size for the job. It’s a compact, gas-fired “Hot Dawg” unit heater with a 45,000 BTU input. Above all, it delivers steady, even heat without taking up valuable floor space. So your plants — or your projects — stay comfortable through the colder months.

Modine has built quality unit heaters since 1916, and the HD45 carries that reputation. For example, it uses a durable aluminised-steel heat exchanger, backed by a 10-year warranty. In addition, a sealed, permanently-lubricated motor keeps it running smoothly for years, with no oiling needed. So it’s a dependable heater you can install once and forget about.

Why Choose the Modine HD45

The HD45 is all about the right heat in a compact, quiet package. To start, it produces 36,900 BTU of output at 82% thermal efficiency. So it warms a small-to-mid space economically. In addition, it’s remarkably quiet — just 57 dBA at 5 feet. As a result, it heats your space without the distraction of a noisy machine.

It’s also designed for easy, tidy installation. For example, the low-profile cabinet is just 31cm (12.2″) high, so it tucks close to the ceiling. Better still, it comes with the two mounting brackets included — unlike the larger models — so you can mount it just 1″ below the ceiling and keep your floor clear. In addition, the gas, electrical and flue connections can be reversed by simply flipping the unit. So it suits left- or right-hand installation. Plus, the power-vented exhaust uses small-diameter vent pipe, which keeps the install straightforward for your gasfitter.

H2: Key Features

• Compact 45,000 BTU input / 36,900 BTU output gas unit heater
• 82% thermal efficiency for economical heating
• Right-sized for small-to-mid greenhouses, 2–2½ car garages, workshops and sheds
• Very quiet operation (~57 dBA at 5 ft)
• Low-profile cabinet — only 31cm (12.2″) high
• Ceiling mounting brackets included
• 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
• Finger-proof fan guard fitted as standard
• Tough aluminised-steel heat exchanger
• 10-year heat-exchanger warranty (2 years parts)

H2: Specifications

• BTU input: 45,000 BTU/hr
• BTU output: 36,900 BTU/hr
• Thermal efficiency: 82%
• Airflow: ~720 CFM
• Heat throw: up to ~8.2m (27 ft)
• Maximum mounting height: ~3m (10 ft)
• Ignition: direct spark, single-stage
• Vent size: 3″ (~75mm)
• Sound level: ~57 dBA at 5 ft
• Heat exchanger: aluminised steel
• Dimensions: approx. 559mm D x 681mm W x 310mm H (22″ x 26.8″ x 12.2″)
• Weight: approx. 27kg (60 lb)
• Warranty: 10-year heat exchanger, 2-year parts
• Note: mounting brackets included; runs 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: HD45 vs HD125 — Which Size Do You Need?

Choosing the right output matters, so it helps to compare. The HD45 (45,000 BTU) is the compact option — ideal for a small-to-mid greenhouse, a 2–2½ car garage, a workshop or a shed. The Modine HD125 (125,000 BTU), by contrast, is built for large commercial greenhouses, big workshops and warehouses. So choose the HD45 for a smaller space, and step up to the HD125 (or a mid-size model) for a large one. Not sure? Then talk to our team — sizing the heater to your space is the key to efficient, even warmth.

H2: Ideal Applications

The HD45 suits a range of smaller spaces. For example, it’s a great choice for a hobby or mid-sized greenhouse, where gentle, steady heat protects crops and extends the season. In addition, it’s perfect for garages, workshops, sheds and small storage spaces. So whether you’re keeping seedlings frost-free or staying warm at the workbench, it delivers the right amount of heat — quietly and efficiently.

H2: Installation, Gas and Safety (Australia)

This part is important, so please read it carefully. The HD45 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 check the electrical supply (the standard US model is 115V), and make sure it suits Australian power or that you have the correct variant. Finally, the unit needs adequate combustion-air ventilation and correct flue venting — another reason professional installation is essential.

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

H2: Frequently Asked Questions

What size space does the HD45 heat? With 45,000 BTU input and a ~8m heat throw, it suits smaller spaces — a small-to-mid greenhouse, a 2–2½ car garage, a workshop or a shed.

How is it different from the HD125? The HD45 is the compact 45,000 BTU model for smaller spaces. The HD125 is a 125,000 BTU heater for large commercial greenhouses and warehouses.

Does it include mounting brackets? Yes. Unlike the larger HD100 and HD125, the HD45 comes with the two ceiling mounting brackets included.

Can it run on LPG? It’s set up for natural gas, but it converts to propane/LPG with 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.

H2: Conclusion

In the end, the Modine HD45 Unit Heater is a compact, quiet and dependable way to heat a small-to-mid greenhouse, garage or workshop. It combines efficient 45,000 BTU heating, a low-profile design with brackets included, near-silent operation 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.