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HYBRID COAL HEATING, Built to Last

Indoor Hybrid Coal Boilers

Indoor hybrid coal boiler systems for efficient coal-fired hydronic heating, designed for durable performance in homes and larger heating projects.

Indoor systems | Hydronic heating | Complete systems

Choose your hybrid coal boiler

Find the right hybrid coal boiler for your project

Compare the automatic, multi-fuel EKO DUO hybrid coal boiler for homes and mid-size systems with the larger EKO DUO Industrial platform for commercial and industrial hydronic heat.

Multi-fuel hybrid heat

EKO DUO

EKO DUO Hybrid Coal Boiler

Automatic self-cleaning hybrid coal boiler for homes and mid-size hydronic systems, with multi-fuel flexibility.

Smallest model: up to 2,500 sq ft

Largest: up to 9,000 sq ft

90% guaranteed efficiency
Automatic self-cleaning rotary burner
Burns coal, pellets, grains, and biomass
TIS tronic smart control and long autonomy

View EKO DUO boilers

Commercial & industrial scale

EKO DUO

EKO DUO Industrial Coal Boiler

Industrial-scale hybrid coal boiler platform for very large buildings, commercial facilities, and high-demand hydronic heat.

Smallest model: up to 15,000 sq ft

Largest: up to 110,000 sq ft

500K to 3400K BTU output
Automatic self-cleaning multi-fuel combustion
Large coal hopper autonomy
Smart hydronic control for high-demand systems

View EKO DUO Industrial boilers

Sizing guide

Compare Hybrid Coal Boiler Models by Coverage

Square-footage ranges are approximate. Final sizing depends on heat loss, insulation, climate, buffer tank design, venting, and how the boiler will be used.

EKO DUO

Model

Approx. coverage

Price

Model link

EKO DUO 15 / 65K BTU Up to 2,500 sq ft 20% OFF $7,457 $5,966 View model EKO DUO 35 / 130K BTU Up to 4,000 sq ft 20% OFF $9,120 $7,296 View model EKO DUO 55 / 200K BTU Up to 6,000 sq ft 20% OFF $10,675 $8,540 View model EKO DUO 95 / 330K BTU Up to 9,000 sq ft 20% OFF $13,181 $10,545 View model

EKO DUO Industrial Coal Boiler

Model

Approx. coverage

Price

Model link

EKO DUO 150 / 500K BTU Up to 15,000 sq ft 20% OFF $25,234 $20,187 View model EKO DUO 300 / 1000K BTU Up to 32,000 sq ft 20% OFF $37,406 $29,925 View model EKO DUO 500 / 1700K BTU Up to 50,000 sq ft 20% OFF $50,468 $40,374 View model EKO DUO 1000 / 3400K BTU Up to 64,000 sq ft 20% OFF $57,237 $45,790 View model

For large or mixed-use buildings, confirm final sizing with MBTEK before ordering.

What is an indoor hybrid coal boiler?

An indoor hybrid coal boiler is an automatic, multi-fuel solid-fuel boiler that burns coal as its primary fuel and can also run on pellets, grains, and biomass, with a manual firebox for wood. It heats water for hydronic systems, sending heat to radiant floors, fan coils, domestic hot water loads, workshops, farms, and building heat.

This is a residential and commercial heating boiler, not a coal-fired power-plant boiler or a coal cooking stove. It is planned as indoor mechanical-room equipment with a chimney, piping, pumps, controls, protection valves, and thermal storage, and selected as a complete hydronic system.

MBTEK EKO DUO hybrid coal boilers for hydronic heating

MBTEK hybrid coal boiler systems are built on the EKO DUO platform. EKO DUO covers homes and mid-size hydronic projects, while EKO DUO Industrial scales up to commercial and industrial heating loads. Both use an automatic self-cleaning rotary cast iron burner, guaranteed 90% efficiency, and the TIS tronic 481R controller that manages combustion, pumps, mixing valves, storage, and hydronic operating modes.

A complete system can include a buffer tank, boiler protection valve, circulator pumps, controls, radiant floor loops, fan coils, air handlers, and an indirect tank for domestic hot water. The product picker and sizing tables above keep those boiler links close to the top so buyers can move from research to model selection quickly.

Hybrid coal boiler vs single-fuel coal boiler

Hybrid (multi-fuel) coal boiler

A hybrid coal boiler can switch between coal, pellets, grains, and biomass as price and availability change, with a manual firebox for wood. That flexibility lets owners chase the lowest-cost fuel each season while keeping one boiler and one hydronic system.

Single-fuel coal boiler

A single-fuel coal boiler is built around one fuel only. It can be simpler, but it cannot adapt when coal supply or pricing shifts. MBTEK positions EKO DUO and EKO DUO Industrial for buyers who want automatic multi-fuel flexibility.

Coal types and multi-fuel options

EKO DUO hybrid coal boilers run on anthracite and bituminous coal in rice, buckwheat, pea, and stoker sizes. The automatic feed handles coal up to 1 1/4", plus pellets, grains, and biomass, and the manual firebox accepts wood logs and peat briquette for added flexibility.

Matching coal size and type to the boiler matters for clean, steady combustion. Confirm the fuel plan with MBTEK so the feed system, hopper autonomy, and ash handling fit how the building will actually be heated.

Sizing, buffer tanks, and installation basics

Square footage is only a starting point. Final hybrid coal boiler sizing should account for heat loss, climate, insulation, ceiling height, air leakage, domestic hot water demand, radiant or fan coil loads, and whether the system is heating a home, shop, farm, or commercial building.

Heat loss Use a heat-loss calculation when possible, especially for large, mixed-use, or poorly insulated buildings.
Thermal storage A buffer tank can store heat, reduce cycling, and improve comfort in many solid-fuel boiler systems.
Chimney plan Confirm flue sizing, draft, clearances, combustion air, and local code before finalizing the mechanical-room layout.
Fuel storage Plan dry coal and fuel storage and a refill routine that matches the hopper autonomy and seasonal demand of the building.

Maintenance basics for indoor coal boilers

Indoor hybrid coal boilers need regular cleaning and annual hydronic service. Quality fuel, clean heat-transfer surfaces, correct draft, and healthy water-side components all affect performance.

Fuel quality Burn the correct coal size and type for the boiler. Poor or oversized fuel reduces efficiency and increases cleaning needs.
Ash handling Empty ash and clean the burner and heat exchanger on schedule. The self-cleaning burner reduces, but does not remove, this task.
Chimney and seals Inspect flue paths, draft, door gaskets, and smoke seals so combustion stays controlled and safe.
Hydronic service Check pumps, valves, controls, expansion tank, water quality, and buffer tank components as part of annual system service.

What is an indoor hybrid coal boiler?

An indoor hybrid coal boiler is an automatic, multi-fuel solid-fuel boiler that burns coal and can also run on pellets, grains, and biomass, with a manual firebox for wood. It heats water for hydronic space heating or domestic hot water and is installed in a suitable indoor mechanical space with a chimney, piping, controls, and safety planning.

How does a hybrid coal boiler work?

A hybrid coal boiler feeds fuel from a hopper into a self-cleaning burner under automatic combustion control, then transfers that heat into water. The hydronic system moves the heat to floors, coils, tanks, or air handlers, while a controller manages pumps, mixing valves, and storage.

What fuels can a hybrid coal boiler burn?

The EKO DUO automatically burns coal, pellets, grains, and biomass, and the manual firebox accepts wood logs and peat briquette. That multi-fuel flexibility lets owners switch fuel based on price and availability while keeping one boiler and one hydronic system.

What type and size of coal does it use?

EKO DUO hybrid coal boilers run on anthracite and bituminous coal in rice, buckwheat, pea, and stoker sizes. The automatic feed handles coal up to 1 1/4". Matching coal size and type to the boiler keeps combustion clean and steady, so confirm the fuel plan during sizing.

How efficient are hybrid coal boilers?

EKO DUO hybrid coal boilers carry a guaranteed 90% efficiency, with a design focused on complete heat recovery and automatic combustion control. Real efficiency in use also depends on fuel quality, draft, sizing, and how well the hydronic system is set up.

Can a coal boiler heat my whole house and hot water?

Yes. A correctly sized hybrid coal boiler can heat an entire house through the hydronic system and support domestic hot water using an indirect tank. A buffer tank and adequate fuel storage help a whole-house system run smoothly with fewer refills and less cycling.

Which EKO DUO hybrid coal boiler should I choose?

Choose EKO DUO for homes and mid-size hydronic projects, and EKO DUO Industrial for commercial or industrial-scale heating. Final selection should be based on heat loss, building type, fuel plan, and hydronic design, so confirm sizing with MBTEK before ordering.

What maintenance does an indoor coal boiler need?

Maintenance includes burning the correct coal, emptying ash, cleaning the burner and heat exchanger, inspecting the chimney and flue, checking door gaskets, and servicing pumps, controls, valves, expansion tank, and water quality. The self-cleaning burner reduces, but does not remove, routine cleaning.

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