MULTI PASS SERIES Outdoor Coal Furnace
The Multi Pass outdoor boilers combines the proven design of a traditional outdoor coal furnace with technology engineered for greater efficiency and cleaner combustion. Built with 409 Titanium Enhanced Stainless Steel, each furnace features a triple-pass water-filled heat exchanger, Turbo Draft System, and cast iron shaker grates with a removable ash pan for efficient heat recovery and easy maintenance.
With multiple models and heating capacities available, the Multi Pass Series provides dependable outdoor heat for homes, shops, garages, barns, greenhouses, commercial spaces, and other applications.
Triple Pass Water Filled Heat Exchanger
The triple-pass water-filled heat exchanger is designed for greater heat transfer and efficiency than conventional units. The triple-pass water-filled heat exchanger is designed for greater heat transfer and efficiency than conventional units. A front-access cleanout door makes it easy to remove fly ash.
Shaker Grates & Ash Pan
A unique cast iron shaker grate and ash pan system is designed to optimize airflow beneath the fire while making ash removal quick and easy. Simply shake the grates to clear excess ash without special tools, allowing it to collect in the extra-large, removable ash pan for easy cleaning and disposal. The ash pan door also features a double safety latch handle for added security.
Adjustable Primary Air Blower
Combustion air is introduced beneath the shaker grates to help increase fire temperatures for a cleaner, more efficient burn. The Adjustable Primary Air Blower regulates the amount of air entering the firebox to maintain proper airflow regardless of the type of fuel being burned. A variable-speed control knob within the control panel allows the airflow to be adjusted as needed.
Extra Large, Insulated, Firebox Door
We designed the Multi Pass Series of outdoor furnaces to feature an extra large firebox door, placed at the optimal height for care free loading. Safety is at the core of everything we develop which is why all of our firebox doors have multiple layers of insulation and are equipped with our roller latch door system.
How the Multi Pass Works
The Turbo Draft System introduces fresh air above the flame, forcing secondary gases downward where they are ignited before entering the triple-pass heat exchanger. This secondary combustion creates higher fire temperatures for a more efficient burn and greater heat recovery, while helping reduce gases that can contribute to creosote buildup. Together, these processes support a cleaner, more efficient burn cycle.
Why Choose A Multi Pass Stove?
Cost-Effective Heat
The Multi Pass maximizes heat recovery and efficiency to deliver more usable heat from every load of fuel while helping reduce heating costs.
Cleaner, More Efficient Combustion
The Turbo Draft System ignites secondary gases above the flame, supporting hotter, more efficient burns while helping reduce gases that can contribute to creosote buildup.
Built for Durability
Manufactured in the USA with 409 Titanium Enhanced Stainless Steel and backed by a 20-Year Limited Warranty, the Multi Pass is built for dependable performance in demanding conditions.
Low Maintenance & Easy Cleanup
The shaker grate system makes clearing excess ash easy, while the extra-large removable ash pan and accessible cleanout doors simplify routine maintenance.
Simple, Controlled Operation
The adjustable primary air blower, digital controls, water level indicator, and large firebox make operation straightforward while helping maintain consistent heat.
Designed for Coal Burning
The cast iron shaker grate and adjustable primary air control support efficient coal combustion by maintaining proper airflow beneath the fire for hotter, longer-lasting burns.
Featuring Turbo Draft System
Residential Homes
Heat your home with a Multi Pass centralized outdoor furnace while keeping wood, ash, smoke, and debris outside.Pools/Hot Tubs
Use your Multi Pass outdoor furnace as part of a properly designed hydronic system for heating pools and hot tubs.Domestic Hot Water
The Multi Pass outdoor furnace can provide heat for domestic hot water when properly installed and equipped.Radiant In-Floor Heating
Deliver consistent hydronic heat through radiant floors in homes, shops, garages, and other buildings with the Multi Pass Series.Commercial Spaces
Heat medium-to-large size commercial buildings and facilities with a properly sized Multi Pass furnace.Greenhouses
Use the Multi Pass furnace to support temperature control and maintain consistent temperatures in greenhouse applications.Garages and Workshops
Comfortably heat detached workspaces, garages, and workshops with the Multi Pass outdoor furnace/boiler.Barns and Agricultural
Provide heat for barns, livestock buildings, and other agricultural spaces with the Multi Pass series.
Multi Pass Series |
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| Model | 7200MP | 7300MP | 7350MP | 7400MP | 7500MP |
| Estimated Weight | 1,450 LBS | 1,800 LBS | 2,050 LBS | 2,500 LBS | 4,000 LBS |
| Width | 49″ | 53″ | 55″ | 61″ | 89″ |
| Length | 61″ | 70″ | 77″ | 81″ | 102″ |
| Height | 87″ | 90″ | 96″ | 100″ | 110″ |
| Firebox Length | 30″ | 38″ | 44″ | 48″ | 60″ |
| Chimney Size | 6″ | 6″ | 6″ | 8″ | 10″ |
| Door Size | 20″ x 20″ | 20″ x 20″ | 20″ x 24″ | 24″ x 24″ | 42″ x 30″ |
| Supply Size | 1 – 1 1/4″ | 2 – 1 1/4″ | 2 – 1 1/4″ | 2 – 1 1/4″ | 4 – 1 1/4″ |
| Return Size | 1 – 1 1/4″ | 2 – 1 1/4″ | 2 – 1 1/4″ | 2 – 1 1/4″ | 4 – 1 1/4″ |
| Water Capacity | 140 Gallons | 180 Gallons | 260 Gallons | 320 Gallons | 600 Gallons |
| Combustion Fan | 150 CFM | 150 CFM | 150 CFM | 150 CFM | 2 x 150 CFM |
| Turbo Fan | 60 CFM | 60 CFM | 60 CFM | 60 CFM | 60 CFM |
| Approximate Sq Ft | 2,000-3,000 | 4,000 - 6,000 | 6,000 – 8,000 | 8,000 - 10,000 | 18,000 – 20,000 |
| Approximate BTU'S | 165,000 | 275,000 | 350,000 | 400,000 | 750,000 |
| Insulation Roof/Walls | R30 | R30 | R30 | R30 | R30 |
| 409 Stainless Steel | Yes | Yes | Yes | Yes | Yes |
| Domestic Coil 300,000 BTU | Optional | Optional | Optional | Optional | Optional |
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How does the Triple Pass Water-Filled Heat Exchanger work?
The Triple Pass Water-Filled Heat Exchanger forces hot exhaust gases through three separate passes before exiting the chimney. This allows more heat to be transferred into the water jacket instead of being lost through the exhaust, improving efficiency while maintaining strong heating performance.
What makes the Multi Pass Series different from the Pristine Series?
The Multi Pass Series is designed to burn coal and other biomass fuels, offering flexibility for different heating needs. The Pristine Series uses advanced gasification technology and is engineered specifically for burning seasoned cordwood with maximum efficiency and low emissions.
What fuels can the Multi Pass Series burn?
The Multi Pass Series is designed to burn coal. Always refer to your owner's manual for a complete list of approved fuels and follow all operating guidelines.
How efficient is the Multi Pass Series?
The Triple Pass Water-Filled Heat Exchanger is designed to capture more heat from the combustion process, helping maximize fuel efficiency while delivering dependable heating performance.
How much fuel does the Multi Pass Series use?
Fuel consumption depends on the size of the furnace, outdoor temperatures, your heating demand, and the type and quality of biomass fuel being burned.
How often does the Multi Pass Series need to be cleaned?
Routine maintenance includes removing ash and periodically inspecting the heat exchanger and chimney. Cleaning frequency depends on usage and the type of biomass fuel being burned.
Does the Multi Pass Series require electricity to operate?
Yes. Electricity powers the blower, circulating pump(s), and electronic controls that regulate furnace operation.
Can the Multi Pass Series provide domestic hot water?
Yes. When installed with the appropriate heat exchanger, the Multi Pass Series can provide domestic hot water while heating your home.
Can I connect the Multi Pass Series to my existing heating system?
Yes. The Multi Pass Series can often be integrated with existing forced-air furnaces, boilers, radiant floor heating systems, and other hydronic heating systems. Your local dealer can recommend the best installation for your home.
What type of fuel provides the best performance?
For the best performance, use clean, dry biomass fuels that are approved for the Multi Pass Series. Following the recommended fuel guidelines helps maximize efficiency and extend the life of your furnace.
What material is the Multi Pass Series made from?
The Multi Pass Series is built from domestically sourced 409 Titanium Enhanced Stainless Steel for exceptional durability, corrosion resistance, and long service life.
What warranty comes with the Multi Pass Series?
The Multi Pass Series is backed by a 20-Year Limited Warranty, providing long-term confidence in your investment.
Can I heat multiple buildings with one Multi Pass furnace?
Yes. With properly sized insulated underground piping, one furnace can heat multiple buildings, including homes, shops, garages, barns, and other structures.
How long can I expect a Multi Pass furnace to last?
With proper installation, routine maintenance, and regular care, a Multi Pass furnace is built to provide many years of dependable heating.
How often do I need to load fuel into the Multi Pass Series?
Loading frequency depends on the outside temperature, your heating demand, and the type of fuel being burned. Coal typically provides long burn times, helping reduce the frequency of refueling compared to some other solid fuels.
How often do I have to clean the ashes out of my MP Series Crown Royal Stove?
Crown Royal Stoves recommends removing ash from the ash pan weekly and the heat exchanger every 2-3 weeks. The less ash in the Heat Exchanger the higher the efficiency.
How often should I use the shaker grates in my Multi-Pass?
Depending on the fuel type and heat demand, typically you should shake the grates once a week after a coal bed is established.
How long of burn times can I get with my Multi Pass unit?
Both the Multi Pass and Pristine series are designed for 12 hour burn times when sized appropriately. Speak to your local dealer for accurate sizing of a unit. A site visit may be necessary to size a unit appropriately.
What temperature settings, differential, and fan speed should be used to burn coal most effectively and efficiently?
All Crown Royal Stoves come with a preset temperature set point of 180 Degrees F with a 10 degree differential. Optimum fan speed for the Multi Pass stove is in the medium to low range as indicated at the rheostat fan speed controller. All coal varies in quality. Most of our customers have found the greatest success with a temperature set point of 180 degrees F with a 1-2 temperature differential, and the fan speed as low as possible to still ignite the coal bed while not blowing out the fire in the coal bed.
What type of coal should I burn in my Multi Pass stove?
The two types of coal recommended to burn in your Multi Pass stove is anthracite and bituminous. Anthracite: also known as hard coal. The highest quality of coal. It is a hard, brittle, and lustrous black coal. Anthracite burns hotter for longer periods of time producing the highest BTUs of any other type of coal. It is also the cleanest burning type of coal. Bituminous: also known as soft coal. Bituminous coal is a middle rank coal between subbituminous and anthracite. Bituminous usually has a high heating (BTU) value. There are different grades of bituminous coal, some that have higher sulfur content than others. Bituminous coal appears shiny and smooth when you first see it but look closer and you may see it has layers.
What size of coal should I burn in my Multi Pass stove?
The best size coal to burn in your Multi Pass stove is Nut coal (13/16’ – 1 5/8” Diameter), Stove coal (1 5/8” - 2 7/16” Diameter), and Egg coal (2 7/16” – 3 1/4” Diameter).
Can I burn larger coal pieces in my Multi Pass stoves?
Yes, as long as a good size coal bed has already been established using smaller sized coal. You may find that smaller coal may burn easier.