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 Book a Ben consultation.

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	78.74 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

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

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 - Heat-Equalizing Sauna Heater with Himalayan Salt 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

Click Image, Then Scroll! For the best experience, click on any image then swipe or use arrow keys to browse.

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

The M3 with its fire chamber extended through the wall, so the stove is loaded and lit from the next room. 16.5 kW for sauna rooms of 212–459 adjusted cubic feet, 66.1 lb of 4–6 in stones, 105.8 lb net, top flue connection at 4.6 in. Harvia’s SL instructions call for a minimum 19.7 in safety distance to the front, and the door’s opening direction can be changed.

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 4.6 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 insulated 21.3 ft steel chimney, sized for this stove. Pick the finish to match the stove or the room.

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:

Built for these

Harvia Sauna Rocks (can only be purchased with heater)
Required, not included. Harvia's stone chart gives 66 lb of 4–6 in AC3020 for a 16.5 kW M SL, two 44 lb boxes. We recommend an extra box so you can choose stones for fit, form and function. See the full product and build your package →
Harvia WL450 – Protective Shield for M1, M2, M3, and M3 SL
The model-specific sheath. The WKM3SL data sheet gives 9.9 in to combustible material at the sides; our WL450 page publishes B 2 in / C 2 in / D 11.9 in with the shield fitted. See the full product and build your package →
Harvia WP220ST Pipe-Model Water Heater | 22 L Stainless Steel
A 22 L stainless tank that sits on top of the stove with the smoke pipe running through it. Harvia states it is compatible with all wood-heated Harvia stoves except the Harvia 50, and this stove has the top flue connection it needs. See the full product and build your package →
Harvia WZ Smoke Pipe, 4.6 in, for Wood-Burning Sauna Stoves (7.9 in, 19.7 in, 3.3 ft)
Matching 4.6 in flue sections in 7.9 in, 19.7 in and 3.3 ft, the chimney connection diameter on this stove's data sheet. See the full product and build your package →

What’s included

Sauna stove
Stove door
Ash box
Fire chamber extension
Installation and operation manual

Every wood-fired sauna has the same nuisance: the fire wants tending and the hot room is where you are trying to sit still. The SL models solve it structurally. In Harvia’s words, they are “designed for people who want to conveniently heat their sauna from another room or outside the building”, and “the opening direction of the door can be changed, making these heaters even easier to use”. The stove body stays in the sauna; its fire chamber extension passes through an opening in a non-combustible wall so the door lands in the next room.

Installation, in Harvia’s words

“Detach the hinge pin and door from the stove. Push the fire chamber extension through the opening far enough to allow attachment of the door.”
Connected to a Harvia steel chimney: “The nonflammable wall through which the stove is installed must extend up to the roof. NOTE! Does not apply to thin nonflammable wall structures that allow to install steel chimney far enough from the wall (for example Harvia Duo glass wall).”
“The safety distance between the inflammable structures and the chimney outer casing must be minimum 4 in.”
Minimum safety distance to combustible material at the front, for SL models: 19.7 in.
Floor protection: “Floor in front of the stove door is made of inflammable material. Install floor protection made of nonflammable material.”
Place firewood on the grate at the back of the fire chamber: Harvia asks you to avoid burning firewood in the fire chamber extension, and not to use excessively long firewood even though it would fit.
Minimum room height 74.9 in.

Specifications

Spec	Value
Output	16.5 kW
Sauna room size	6.0–42.7 ft³ (212–459 adjusted cubic feet)
Dimensions (W x D x H)	15.4 x 25.6 x 28 in
Net weight	105.8 lb; gross 111.6 lb
Stones	66 lb, Ø10–6 in, two 44 lb boxes of AC3020 cover it
Maximum log length	13.7 in
Flue connection	Top; chimney connection diameter 4.6 in
Clearance, front (SL instructions)	19.7 in to combustible material
Clearance, sides	9.9 in combustible, 4 in non-combustible
Clearance, rear	11.9 in
Clearance, ceiling	47.3 in
Minimum room height	74.9 in
Color	Black
Certification	CE, EAC
GTIN / UPC	6417659001151

Common questions

Do I need to add rocks, or does the stove already come with them?

Sauna stones are not included with the Harvia M3 SL and are ordered separately. Harvia's heater and stone chart calls for a minimum of 66 lb of 4–6 in stones for a 16.5 kW M SL, which is two 44 lb boxes of AC3020, and the WKM3SL data sheet gives the same 66.1 lb at Ø4–6 in. We recommend an extra box, because each natural stone is a different shape and size and the spare lets you choose for fit, form and function. What is in the carton is the stove, the stove door, the ash box, the fire chamber extension and the installation and operation manual.

Often bought with the Harvia Sauna Rocks (can only be purchased with heater)

What customers building this room most often add alongside it.

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