Expert help that stays with you

Whether you’re choosing one component or planning the whole room, small details can become expensive problems once installation begins. We know the products we sell and the questions to ask early, helping catch mismatched components, overlooked requirements, and installation issues while they are still easy to fix.

Our job does not end when your order ships. We stay available through installation and beyond. If something needs attention, we stay involved, work the problem, and help see it through.

We want you to feel good about choosing Sauna Marketplace long after your first session, and confident recommending us to a friend. That standard guides the advice we give, the products we sell, and the way we take care of our customers.

Sauna and heater customers also receive free shipping on sauna accessories for life.

Planning a sauna, or need help with one you purchased from us? Our founders have assembled many of the saunas we sell, visited the manufacturers, and use these products every day. New customers and existing Sauna Marketplace sauna and heater owners can Open the 3D planner.

Includes

What Is Included

All configurations

Included with purchase

Sauna stove, stove door, ash box, fire chamber extension, installation and operation manual.

Required separately

66 lb of split-face sauna stones (quantity 2 × 44 lb of 4 to 6 in stones).

Contents vary by configuration. Check the row for the option selected above.

Technical Specifications

Model & Application

Model & Application
Brand	Harvia
Catalog Product	Harvia M3 SL Wood-Burning Sauna Stove \| 16.5 kW Through-Wall Feed (WKM3SL)
Heater Type	Wood-burning sauna stove
Model Number	M3 SL
SKU / Part Number	WKM3SL

Electrical

Electrical
Rated Power	16.5 kW

Dimensions & Weight

Dimensions & Weight
Depth	25"
Minimum Host-Room Height	74.9 in
Product Weight	105.8 lbs

Stone Capacity & Performance

Stone Capacity & Performance
Stone Capacity	66 lbs

Installation Clearances

Installation Clearances
Ceiling-Clearance Reference Height Above Finished Floor	27.95 in
Ceiling-Clearance Reference Plane	Stove Top
Minimum Ceiling Clearance Above Reference Plane	47.24 in

Through-Wall Installation

Through-Wall Installation
Wall Opening, Minimum	8.7 in wide x 15.4 in tall from the floor (220 x 390 mm).
Wall Thickness, Maximum	5.9 in (150 mm); concrete or brick.
Non-Combustible Wall Around the Opening, Minimum	23.3 in (590 mm) beside the opening and 54.8 in (1390 mm) overall width (Harvia SL Additional Instructions, dimensions D and E).
Steel Chimney Note	With a Harvia steel chimney the non-flammable wall through which the stove is installed must extend up to the roof (thin non-combustible partitions such as the Harvia Duo glass wall excepted).

Included & Required

Included & Required
Included Components	Sauna Stove, Stove Door, Ash Box, Fire Chamber Extension, Installation and Operation Manual
Required, Not Included	66 lbs of Split-Face Sauna Stones (Qty 2 x 44 lbs of 4 to 6 in stones)

Certifications

Certifications
Certifications & Listings	CE, EAC

Warranty

Warranty
Residential Warranty	Warranty

Use the attached current manual and a qualified installer for final sizing, wiring, clearances, venting, and local-code compliance.

How It Fits

How This Product Fits the System

What it is used for

A wood-burning sauna heater that heats the room and stone mass for traditional löyly. Treat the stove, chimney, floor protection, clearances, combustion air, ventilation, and stones as one installation system.

What to plan

Through-wall opening: at least 8.7 in wide x 15.4 in tall from the floor (220 x 390 mm) in a concrete or brick wall no more than 5.9 in (150 mm) thick, with the non-combustible wall continuing at least 23.3 in (590 mm) beside the opening (54.8 in / 1390 mm overall).
Size from adjusted sauna volume, including the effect of glass, masonry, and other uninsulated surfaces; do not size from floor area alone.
Match the selected model's power or fuel, voltage, phase, circuit, wire, control, stone, and venting requirements before ordering.
Treat clearances, ceiling reference planes, ventilation, guarding, floor protection, and service access as one room-layout decision.
Follow the current installation manual and use a qualified installer.

Required separately

Complete the system with these items.

Harvia Sauna Rocks (can only be purchased with heater) Required for operation; match the version and quantity to this selection.

Designed to work with

Model-specific replacements and compatible system components.

Harvia HSP3M Safety Railing for Harvia Spirit | Heat-Treated Birch Designed for the same heater or control system; confirm compatibility with the selected model.
Harvia HL3M Safety Rail for Virta HL110, HL70SA and HL90SA | Wood Designed for the same heater or control system; confirm compatibility with the selected model.

Optional accessories

Optional upgrades and accessories.

Harvia WZ115155 Wood Stove Pipe Adapter 4.5" Euro to 6" USA Optional accessory; confirm model compatibility and room layout before adding it.
Harvia Chimney Kit in Black or Stainless Steel - WHP4921.3 ft Optional accessory; confirm model compatibility and room layout before adding it.
Harvia M3 Protective Bedding, Black Optional accessory; confirm model compatibility and room layout before adding it.
Harvia WL450 - Protective Shield for M1, M2, M3, and M3 SL Optional accessory; confirm model compatibility and room layout before adding it.
Saunum AirSolo Optional accessory; confirm model compatibility and room layout before adding it.
Harvia WZ Smoke Pipe, 4.6 in, for Wood-Burning Sauna Stoves (7.9 in, 19.7 in, 3.3 ft) Optional accessory; confirm model compatibility and room layout before adding it.
Harvia WHP270 Insulated Smoke Damper for Steel Chimneys, Stainless or Black Optional accessory; confirm model compatibility and room layout before adding it.
Harvia WHM25 Chimney Vapor Barrier Optional accessory; confirm model compatibility and room layout before adding it.
Harvia WZ115030SP Damper Plate for Wood-Burning Sauna Stoves Optional accessory; confirm model compatibility and room layout before adding it.
Harvia WZ020115 Lead-Through Flange for Smoke Pipes Optional accessory; confirm model compatibility and room layout before adding it.
Harvia AC4000 White Decorative Sauna Stones, 2–3.9 in, 22 lb Box (With Heater Purchase Only) Optional accessory; confirm model compatibility and room layout before adding it.
Harvia WP220ST Pipe-Model Water Heater | 22 L Stainless Steel Optional accessory; confirm model compatibility and room layout before adding it.

Other heater options

Compare these options; sizing, power, controls, clearances, and stones may differ.

Harvia M3 Wood Fired Sauna Stove A related heater option, not an interchangeable replacement; re-check sizing, power, controls, clearances, and stones.
Harvia Linear 22 GreenFlame A related heater option, not an interchangeable replacement; re-check sizing, power, controls, clearances, and stones.
Harvia Legend 150 A related heater option, not an interchangeable replacement; re-check sizing, power, controls, clearances, and stones.
Harvia Legend 240 GreenFlame A related heater option, not an interchangeable replacement; re-check sizing, power, controls, clearances, and stones.
Harvia Virta Pro 16 | 240V Single‑Phase Commercial Sauna Heater A related heater option, not an interchangeable replacement; re-check sizing, power, controls, clearances, and stones.
Harvia Club Series A related heater option, not an interchangeable replacement; re-check sizing, power, controls, clearances, and stones.
Saunum Air L Stainless Climate-Equalizing Sauna Heater A related heater option, not an interchangeable replacement; re-check sizing, power, controls, clearances, and stones.
EOS Mythos S45 Design Sauna Heater | 12 / 15 kW A related heater option, not an interchangeable replacement; re-check sizing, power, controls, clearances, and stones.

Attachments

Gallery

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Harvia M3 SL Wood-Burning Sauna Stove | 16.5 kW Through-Wall Feed (WKM3SL)

Name: Harvia M3 SL Wood-Burning Sauna Stove | 16.5 kW Through-Wall Feed (WKM3SL) | SaunaMarketplace.com
SKU: WKM3SL
Price: 1416.00 USD
Availability: InStock

Harvia M3 SL is a 16.5 kW wood-burning sauna stove for 212 to 459 adjusted cubic feet. Its fire chamber extends through a noncombustible wall so you can load the fire from the adjoining space. It holds up to 66 lb of stones, sold separately.

Configure the stove, protection, chimney and water heater in 3D, then add the selected package to your cart.

Build Your Quote:

$1,416.00

Add the required stones: M3 SL

The M3 SL takes 66 lb of 4 to 6 inch stones and none come in the box, which is two boxes. Stack them loosely so air can move between them and the fire chamber stays covered, and plan on restacking once a year.

I already have the approved 4 to 6 inch stones

2 boxes of Harvia AC3020 stones, 44 lb each (88 lb supplied)(+$124.00)

Pipe adapter for North American chimney parts

The stove leaves the factory with a 4.5 inch European flue collar and North American chimney parts are 6 inch. This adapter joins the two. Skip it if your chimney is already sized to the European pipe.

Harvia WZ115155 adapter, 4.6 in Euro to 6 in USA +$105.00

Chimney kit

Harvia’s matching chimney kit includes 59.1 in of insulated chimney plus a 39.4 in uninsulated connector. Choose stainless steel or black. The final chimney schedule and roof assembly determine any additional components.

Harvia WHP1500 chimney kit, stainless steel +$1,487.00

Harvia WHP1500M chimney kit, black +$1,578.00

Floor protection

Needed when the stove sits on a waterproofed tile or hardwood floor. Aluminum-zinc coated steel, 17.7 by 26 inches, sized to the M3 footprint.

Harvia WL100 protective bedding, black +$316.00

Wall protection for tighter clearances

The model-specific sheath. It mounts to the stove and shortens the safety distance to combustible walls, which is what saves the build when the room is tight.

Water heater

A 5.8 gallon stainless tank that sits on the smoke pipe and heats off the flue. The M3 SL has the top flue connection it needs.

Harvia WP220ST pipe-model water heater +$727.00

Zero Interest Payments:

Pay with HSA/FSA:

Your Harvia M3 SL, configured around your sauna

The M3 SL keeps the stove body in the sauna and moves the loading door through a noncombustible wall. The firewood is loaded from the adjoining space.

Configure your Harvia M3 SL and accessories in 3D ↑

Choose where you load the fire

Choose the in-room M3 if you want the loading door inside the sauna. The SL is a separate stove with its own fire chamber extension, top flue connection and through-wall installation requirements.

See the actual installation and your selected package

The 3D view shows the M3 SL, its loading extension and supported accessory choices. Use it to understand how the stove, protection and flue fit together.

Enter your room dimensions and uninsulated surface area, compare the layout and review the selected components. The configurator keeps the package choices together; your installer confirms the foundation, wall construction, ventilation and complete chimney route.

Build the whole installation

Stones: add two 44 lb boxes of Harvia AC3020. The stove holds up to 66 lb, so keep the surplus rather than loading all 88 lb. Use the specified 4 to 6 in sauna stones and leave air passages between them.
Floor protection: Harvia WL100 protective bedding protects the supporting surface where the stove instructions require it. Protection in front of the loading door is a separate part of the floor plan.
Wall protection: Harvia WL450 protective sheath surrounds the stove to reduce the applicable wall clearances. It does not remove chimney, ceiling or loading-door clearances.
Chimney system: choose the matching WHP1500 chimney kit in stainless steel or black, or the flat-roof and barrel chimney package. These are alternative complete kits, so choose one. The WHP1500 has 59.1 in of insulated chimney plus a 39.4 in uninsulated connector. Its cap and specified roof/ceiling components are included; the WHM25 vapor-barrier collar is separate.
Chimney height and roof: add the measured 39.4 in extension, 19.7 in extension, WHM25 vapor-barrier collar, insulated damper and the appropriate roof components. Keep joints outside the ceiling and roof penetration; the chimney schedule determines the parts and support.
A different chimney system: the WZ115155 adapter connects the stove-size pipe to a 6 in system. It is an alternative to the matching Harvia kit, not an extra fitting needed with that kit. The installer must approve the complete connection and listed chimney system.
Hot water: the optional WP220ST pipe-model water heater holds 5.8 gallons and heats water from the flue. Its upper connector needs the radiation protection or combustible-material distance specified in the tank manual. Keep water in the tank while heating.

Use Harvia WHP chimney systems only for standalone outdoor sauna buildings. For a residence or attached building, use an installer-designed chimney system approved for that application.

Plan the floor, walls and ceiling together

Keep at least 47.25 in between the stove top and the ceiling. Include any protective bedding and foot adjustment when checking the installed height. The protective sheath changes only the clearances specified for that exact assembly. Combustible materials, noncombustible walls, the loading door and connecting pipe have separate requirements.

The SL extension passes through a concrete or brick wall no more than 5.9 in thick. The minimum opening is 8.67 in wide and 15.36 in high above the stove support level. Add the installed base height when measuring from the finished floor; WL100 adds 2.36–2.96 in. Its diagrams also define the required noncombustible wall extent. Follow the full SL wall, loading-side floor and chimney instructions; do not substitute an ordinary wood-framed opening.

Keep the M3 serviceable

The door glass, cast-iron grate, ash box, handle, hinge pin and soot-opening cap are separate service parts. Match the part to the stove model and revision before ordering. The replacement glass is the pane only; a glass pane and a complete door are different parts. Empty the ash box as directed, inspect the flue and keep combustion-air passages clear.

View the Harvia stove-parts drawing. Current service-part ordering information is in the 3D configurator’s parts section.

What comes with the stove?

The stove includes its door, ash box and installation instructions plus the fire chamber extension. Stones, protective bedding, wall sheath, chimney system and water heater are selected separately. Two boxes of stones supply extra material for a permitted 66 lb charge; the supplied box weight is not the amount to load.

Read the current Harvia M-series installation and operation manual. Use the model table and the separate SL instructions for the exact stove selected.

Planning guides: Sauna heater calculator Wood sauna stove guide

Expert help that stays with you

Our job does not end when your order ships. We stay available through installation and beyond. If something needs attention, we stay involved, work the problem, and help see it through.

Sauna and heater customers also receive free shipping on sauna accessories for life.

Includes