Modine HD45 Unit Heater

Item No. HD45A-01
Free Shipping See Details Model HD Hot-Dawg Unit Heaters: For applications requiring a low profile unit. The Hot Dawg may be installed in residential, greenhouse or commercial applications just one inch below the ceiling. Don't be fooled by cheap Chinese manufactured heaters currently flooding the
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Model HD Hot-Dawg Unit Heaters: For applications requiring a low profile unit. The Hot Dawg may be installed in residential, greenhouse or commercial applications just one inch below the ceiling. Don't be fooled by cheap Chinese manufactured heaters currently flooding the market. Since 1916, Modine has provided quality heating solutions that are made in America to the highest possible standards. The superior quality matched with the following features makes the Hot Dawg unit heater an easy choice for a variety of applications.

Standard Features

  • Made in the USA Made in the USA
  • Certified for residential, agricultural and industrial use.
  • Quiet operation.
  • Attractive low-profile design and neutral paint scheme assure that Hot Dawg will blend inconspicuously into any garage decor.
  • Durable polyester-powder paint maintains life-long good looks.
  • Standard power exhaust simplifies side-wall or roof venting with small-diameter vent pipe.
  • Versatile design allows for right or left-hand piping and installation. Gas, electrical and flue connections can be changed from one side to the other by simply flipping the Hot Dawg over.
  • Lightweight, easily installs from ceiling with only 2 angle brackets (included).
  • Installs quickly and easily with field wiring connections and knockouts for quick access to gas and electricity.
  • Designed for natural or propane gas.
  • Sealed, permanently-lubricated motor for trouble-free dependability.
  • Full 10-year warranty on heat exchanger.
  • 24,000 thru 75,0000 (HD25A - HD75A) BTUH Heaters will include ceiling mounting brackets. Ceiling mounting brackets for the 100,000 & 125,000 (HD100A, HD125A) BTUH Heaters must be purchased separately.

Dimensions and Diagrams

Dimensions, Diagrams and Specifications (PDF)

Modine Greenhouse Heating Solutions (PDF)

Wiring Diagrams (PDF)

Performance Specifications

ModelApplicationInput BTUHOutput BTUHVent SizeWeight (lbs)
HD301 to 1-1/2 Car Garage
or up to 250 SF Greenhouse.
30,00024,600Requires 3" Vent Pipe55
HD452 to 2-1/2 Car Garage
or up to 350 SF Greenhouse.
45,00036,900Requires 3" Vent Pipe60
HD603 to 3-1/2 Car Garage
or up to 550 SF Greenhouse.
60,00049,200Requires 3" Vent Pipe80
HD75Large Garage
or up to 650 SF Greenhouse.
75,00061,500Requires 3" Vent Pipe85
HD100Up to 1000 SF.100,00082,000Requires 4" Vent Pipe125
HD125Up to 1200 SF.125,000102,500Requires 4" Vent Pipe125


Many of our customers happily report that purchasing a Hot Dawg heater from the Greenhouse Megastore helped them save 50% or more off the unit price received from a local HVAC installer.  However, for safety reasons and to minimize installation problems Modine strongly recommends having a licensed HVAC technician install your Hot Dawg heater.  Although we are happy to offer limited technical support for your Hot Dawg purchase, we can NOT install the heater for you over the phone nor are we able to troubleshoot problems you may experience if you choose to install the heater yourself.  By purchasing this heater from us, you accept sole responsibility for installation and agree to abide by Modine's limited Warranty


Based on our experience in selling Modine Hot Dawg Heaters, we have written up a troubleshooting guide that deals with the issues we most commonly hear from customers. - Troubleshoot a Modine Hot Dawg

If you still need help, check out Modine's own troubleshooting guide.

Comparison Chart

Modine HD-Series vs. Sterling RF-Series

SpecificationModine HD-SeriesSterling RF-SeriesComments
BTU Range30 - 125 MBH30 - 90 MBHModine covers more applications
Minimum Efficiency80%80%Same non-condensing high efficiency
Blower Fan Units
(HDB model only)
60 - 125 MBHNot AvailableModine covers more applications
Casing PaintPolyester PowderWet EnamelModine units will look better longer
Quiet Swept Wing Fans100 and 125 MBHNot AvailableLarger Modine units are quieter
Heat Exchanger Gauge18 Gauge20 GaugeModine heat exchangers are heavier gauge
Optional Stainless SteelYesNot AvailableModine covers more applications for corrosive environments
T.E. Fan Motor StandardYesNoModine motors are protected for longer life
Power Vented X-Changer Warranty
(HDS and HDC models only)
10 Years10 YearsSame 10 year heat exchanger warranty
Sep. Comb. X Changer Warranty
(HDS & HDC models only
10 Years5 YearsModine separated combustion units warrantied longer
Component Warranty2 Years1 YearModine parts warrantied longer

Additional Information


Residential Owners Manual (PDF)


Modine offers a 10 year limited warranty on the heat exchanger and a 2 year limited warranty on all other components.  Please note this warranty covers parts only and does not cover any labor costs associated with repairing the heater. View Warranty (PDF)

Product Video 

Heater Warranty and Return Policy

It is the customer's responsibility to carefully inspect heaters for damage before accepting delivery since heaters are usually not returnable once delivery is accepted. Obviously damaged heaters should be refused and Greenhouse Megastore customer service contacted to make arrangements for a replacement unit. Once delivery is accepted Greenhouse Megastore will gladly provide replacement parts under the manufacturer's warranty to repair damaged or defective heaters; however this warranty does not include any labor costs associated with installing these parts. Warranty issues should be diagnosed by a certified HVAC technician since parts deemed not to be defective by the manufacturer are not available for credit back to the customer. Specific warranty policies vary by manufacturer but typically cover replacement parts as indicated above up to one year after purchase. Please contact Greenhouse Megastore customer service if you have any questions about the warranty for your specific heater.


Free Shipping 

This item ships free via Motor Freight Carrier - almost anywhere in the Continental United States!

On rare occasions addresses with limited access such as islands or major metropolitan areas (ie: New York City) may incur additional delivery fees; if so, you will be contacted to confirm the extra shipping cost before your order is processed. Shipments to Alaska or Hawaii qualify for free shipping to any West Coast port. Please contact us for special shipping rates from the West Coast to Alaska or Hawaii.

Motor Freight Agreement

  • Full Size Semi: Your location must be able to accommodate a full size semi-truck trailer of up to 70ft. in length.
  • Someone Must Be Present: You or someone else authorized must be present to unload the shipment. Exact delivery date will be arranged via phone by freight company.
LTL Freight Type FREIGHT
Standard Drop Shipment Code DROP SHIP
Replenishment System Purchase
Available for Drop Shipment Yes
Item Tracking Code PARENT
Reviews (14)
  • Love this Little Guy
    I installed this unit in my garage so I could have heat to work in there for the winter. It's a 30'x60' and this little guy has NO problem heating it to 70F. I kept on at 45F for the winter to keep the cars and tractor warm and melt snow, and it didn't even make a noticeable bump in the heating bill. It was easy to install and just works. I would recommend this many times over.
  • fantastic heater
    This was purchased to heat an attached 3 car garage (almost 800 sq/ft). It does a fantastic job; it's quiet and heats up to whatever temperature i've set so far. It's definitely a high quality heater. I looked at the local brands of heater available at menards and I was concerned that in the future parts availability may be a problem, but modine is an established brand and should be around a long time. Its cheap to upsize the unit but i reccomend sticking to manufacturer recomendations for sizing
  • Modine HD45 Unit Heater
    This little heater is amazing. I wish I had found this years ago. We will install many more of these in the future. Easy installation, works great, nice looking, it has it all!!!
  • Great Heater
    I bought this heater for my 10x20 foot greenhouse. My husband got in installed right before we had the coldest weather in over 30 years. It did a great job! I would recommend this heater to anyone needing to heat a greenhouse, shop or garage.
  • Great service and price
    After fully researching my needs for a heated 2.5 car garage I selected the Modine Hot Dawg propane heater supplied by Greenhouse Megastore. I learned to spend the extra money on the Modine as opposed to Mr. Heat. The unit arrived promptly with no shipping defects. I did not order the extra complete set of venting components, believing I could purchase units from a home supply store for less. That was not case. I will now be placing an order with Green house for the quality vent pipes.
  • As expected
    Great service and fast shipping. High altitude kit was shipped after the fact at no charge with fast shipping time. Thanks!!
  • Worth The Price!
    Purchased for our restaurant, whisper quiet, great heat. Keeps our whole 30 X 40 building warm. Very easy to install, completed in about 2 hrs.
  • problem solver
    I purchased the 45,000 BTU HotDawg. The compact size ,ease of install and purpose for this unit will work perfectly for my residential application. I will use this heater , NG forced vent in my large attic to keep me warm during the cold winter days and evenings .When not in use I will turn the thermostat to 45 F. With in 5 minutes of the unit being on (very quiet) I'm back in business. Thank you Modine,Big Bear
  • Best Purchase EVER!!!
    When I purchased my Modine Hot Dawg Natural Gas furnace a couple of years ago, I got it for my greenhouse. I actually got a low-profile one for garages, as that is what I needed for the ceiling height, yet still be above the water sprayers, and it has worked marvelously. In Oregon these heaters are priced at $1000 and up, yet even with shipping I was able to save 45% by purchasing it through MegaStore! My husband installed it and we've had no problems's the BEST purchase for my greenhouse we've made yet! I LOVE IT!!!
  • Great Garage Heater
    I ordered this product online and was impressed by the reviews about the product and the Mega Store satisfaction comments. When I received the billing information the invoice showed that the heater would need a high altitude conversion kit. The box was delivered well packed with a sticker that said additional parts included. The conversion kit was included, sized for the altitude of my garage (thanks Google) and the installation was a snap. In short I recommend the product, my garage shop is a large two car and the heater keeps it toasty even in very cold conditions; I also highly recommend the Mega Store.
  • Absolutely Best Purchase Ever
    I purchased the Modine 45 heater and installed April 2007. It is the best quiet most efficient heater I have ever used. I also purchased the horizontal vent kit with heater. The entire installation including running the gas line was simple, took total 5 hours. Very pleased highly recommend to everyone I know.
  • Nice Heater
    Mounts out of the way above. I have a hd45 in my 24x16 garage. I have been running mine for 4 years. Recommended it to 2 friends who purchased 1 hd45 & 1 hd60 both are happy as well, 2 of us run propane the other Nat-Gas.
  • Good service
    We received the product on time. One of the louvers was bent and a spring was missing, but they replaced the parts immediately by express service to arrive at the same time our installation people were due. Job well done by Customer Service!
  • Best Price Around
    Great purchase, the only thing I would do different if I were to do it over is purchase the vent kit with the heater. Modine Quality and MegaStore Value! Product was well packaged and made it to Alaska without damage.