Harvia PRO 20 SL Pro Series Sauna Wood-Burning Stove w/ Exterior Feed
The Harvia PRO 20 SL is a 24.1kW wood-burning sauna stove for rooms from 283 to 706 cubic feet with an exterior feed fire chamber that passes through the sauna wall - the SL variant of the PRO 20 platform. The stove body with stone cage, cast-iron glass door, and radiant surfaces sits inside the sauna room. The fire chamber extends through the wall so wood is loaded from an adjacent room or outdoors, never from inside the sauna. The cast-iron glass door faces outward - the person in the adjacent room can watch the fire while the bathers inside the sauna experience the heat and steam. The reversible door direction is set during installation. Sauna stones (88 lbs, 2 boxes of AC3020, 10-15 cm) are required and sold separately. Delivery is by scheduled pallet freight.
SL exterior feed - two rooms, one fire
The PRO 20 SL's defining capability is described precisely by Harvia: someone can enjoy the sauna while another person relaxes in the next room enjoying the fireplace. The SL fire chamber extension through the wall creates two simultaneous experiences from a single fire - the sauna room bathers receive the heat, steam, and radiant warmth of the 24.1kW stove with its 88-lb stone mass; the person in the adjacent room sees the fire through the cast-iron glass door and benefits from the radiated warmth of the firebox exterior. This dual-room dynamic is specific to the SL configuration - the standard PRO 20 has an interior firebox door facing into the sauna with no fireplace effect in an adjacent room. For sauna buildings with a combined sauna-lounge, cabin saunas with an adjoining relaxation room, or any layout where the fire should be both visible and accessible from outside the sauna, the PRO 20 SL is the purpose-built solution.
PRO 20 platform - vigorous sauna bathing, tight safety distances
The PRO 20 SL shares the complete PRO 20 platform specification. At 24.1kW for rooms from 283 to 706 cubic feet, the stove is designed for vigorous sauna bathing - the high output that brings a 283 cu ft room to temperature quickly and sustains intense bathing temperatures in a 706 cu ft space throughout the session. The large stone compartment with 88 lbs of AC3020 stones produces dense, hearty steam for high-intensity sauna use. The safety distances are among the tightest in the Harvia wood stove lineup: 4" from sides, 4" from back, and 12" from the front to combustible materials - allowing flexible bench placement within the room. The WL550 protective shield accessory (sold separately) is compatible and reduces clearances further when installed.
Reversible door and top or back flue connection
The cast-iron glass door opening direction is reversible - set during installation to suit the room layout and the direction the door faces from the adjacent room. This means the door swing can be optimised for access to the firebox from either side without ordering a specific handed configuration. The stove supports both top flue and back flue connection, selected during installation to match the chimney routing. All Harvia wood stoves use a 115mm (4.5") European standard flue outlet; a 6" (155mm) North American adapter is required and sold separately. Maximum firewood length is 15" with a diameter of 3" to 6". A licensed or certified chimney professional is recommended for all flue installations.
24.1kW wood-burning sauna stove for rooms from 283 to 706 cubic feet. SL exterior feed - fire chamber extends through sauna wall, wood loaded from adjacent room or outdoors. Cast-iron glass door faces outward - fireplace view from adjacent room while sauna bathers enjoy heat inside. Reversible door direction. No electricity required. Large stone compartment - 88 lbs stones required (2 boxes AC3020 10-15 cm, sold separately). Safety distances: 4" sides, 4" back, 12" front. Top or back flue connection. Max firewood 15" / 3-6" diameter. 115mm flue - 6" adapter required for North America (sold separately). WL550 protective shield compatible. Pallet delivery - scheduled freight required. 2-year warranty (consumer). CE certified. Made in Finland by Harvia.
24.1 kW 283 to 706 cu ft SL - exterior feed through sauna wall Wood loaded from adjacent room or outdoors Cast-iron glass door faces outward - fireplace view Reversible door direction Wood-burning - no electricity required Large stone compartment - vigorous sauna bathing 88 lbs AC3020 stones required (2 boxes, 10-15 cm) Safety: 4" sides, 4" back, 12" front Top or back flue connection Max firewood 15" / 3-6" diameter 115mm flue - 6" adapter required for North America WL550 protective shield compatible Pallet delivery required 2-year warranty (consumer) CE certified - made in Finland
⚠️ 88 lbs AC3020 stones (2 boxes, 10-15 cm) required - not included. 6" North American flue adapter required - not included. Pallet delivery. Stones and the 6" adapter must be purchased separately. An additional box is recommended. This stove ships by scheduled pallet freight - a delivery appointment is required. Plan for on-site assistance to move the stove from the pallet delivery point to its installation position. A licensed chimney professional is recommended for all flue installations.
ℹ️ PRO 20 SL vs PRO 20 - exterior vs interior feed, same stove otherwise. PRO 20 WKPR20M: interior feed - firebox door faces into the sauna room, wood loaded from inside during the session. PRO 20 SL WKPR20SLM (this listing): exterior feed - fire chamber extends through the sauna wall, wood loaded from outside, cast-iron glass door faces the adjacent room for a fireplace view. Both share identical output (24.1kW), room range (283-706 cu ft), stone requirement (88 lbs, 2 boxes AC3020), safety distances, and specifications. Choose the SL for any installation where loading wood without entering the sauna room is preferred, or where the fireplace view from an adjacent room is a design goal.
Specifications
Performance
| Power output |
24.1 kW |
| Fuel type |
Wood - no electricity required |
| Room volume |
283 to 706 cu ft |
| Stone capacity |
88 lbs (2 boxes AC3020, 10-15 cm) - sold separately |
| Max firewood length |
15" (390mm) |
| Firewood diameter |
3" to 6" (80-150mm) |
SL exterior feed
| Firebox access |
From outside the sauna room via wall extension |
| Glass door faces |
Adjacent room - fireplace view from outside sauna |
| Door direction |
Reversible - set during installation |
| Dual-room effect |
Sauna heat inside + fireplace view outside simultaneously |
Safety distances (to combustible materials)
| Front |
12" (300mm) |
| Sides |
4" (100mm) |
| Back |
4" (100mm) |
| With WL550 shield |
Reduced further - see Safety Sheet document below |
Flue and installation
| Flue connection diameter |
115mm (4.5") - standard European |
| Flue connection position |
Top or back - selected during installation |
| North American adapter |
6" (155mm) adapter required - sold separately |
| Delivery |
Scheduled pallet freight - appointment required |
PRO 20 SL vs PRO 20 comparison
| Feed direction |
SL: Exterior (through wall) | PRO 20: Interior (sauna room) |
| Glass door faces |
SL: Adjacent room | PRO 20: Into sauna room |
| Output, room range, stones |
Identical - 24.1kW, 283-706 cu ft, 88 lbs (2 boxes AC3020) |
| Safety distances, flue, delivery |
Identical |
Optional accessories (sold separately)
| North American flue adapter |
Harvia WZ115155 (6" / 155mm) |
| Protective shield |
Harvia WL550 (specific to Pro 20 / Pro 20 SL / Pro 20 Duo) |
| Pipe-mounted water heater |
Harvia WL200 or WL300 |
| Flue pipe extensions |
Harvia WZ11520, WZ11550, WZ115100 |
What's included
Harvia PRO 20 SL wood-burning sauna stove with exterior feed fire chamber
Cast-iron framed glass door (reversible direction)
Ash box
Adjustable feet
Installation and operation manual
2-year limited warranty (consumer use)
Required (not included): 88 lbs AC3020 stones - 2 boxes, 10-15 cm (additional box recommended); 6" North American flue adapter (Harvia WZ115155). Optional accessories (sold separately): WL550 protective shield; pipe-mounted water heater (WL200 or WL300); flue pipe components (WZ11520, WZ11550, WZ115100). A licensed chimney professional is recommended for all flue installations.
Why the Harvia PRO 20 SL stands out
Sauna and fireplace - one fire serves two rooms
The PRO 20 SL's through-wall fire chamber creates two simultaneous experiences from a single fire. Inside the sauna: 24.1kW of wood heat, dense steam from 88 lbs of AC3020 stones, and all the sensory qualities of a wood-fired sauna session. In the adjacent room: the cast-iron glass door provides a direct fireplace view of the burning fire with the radiated warmth of the firebox exterior. No other configuration produces this dual-room dynamic without two separate fires.
Undisturbed sauna sessions - wood loaded from outside
Loading wood from outside the sauna room means the firebox can be tended, wood added, and the fire adjusted without opening the sauna door and disturbing the bathing session or losing heat. In a cabin sauna with a relaxation room or lounge adjacent, this means one person can maintain the fire from the lounge while bathers in the sauna are completely undisturbed. The reversible door direction means the firebox opening can face whichever direction the specific room layout requires.
24.1kW for vigorous bathing - tight safety distances
The 24.1kW output positions the PRO 20 SL for vigorous sauna bathing in rooms from 283 to 706 cu ft. The tight safety distances - 4" sides, 4" back, 12" front - give designers maximum flexibility in bench placement relative to the stove within the room. The WL550 protective shield (sold separately) reduces clearances further when installed, providing even more bench layout options in tighter sauna room configurations.
Reversible cast-iron glass door
The cast-iron glass door can be reversed to open left or right - set at installation to suit the access direction from the adjacent room or the firebox approach path. The cast-iron frame provides the thermal durability and mass required at the sustained high temperatures of a 24.1kW wood fire. The glass allows the fire to be visible throughout the session - an essential feature for the fireplace aesthetic the SL configuration is designed to deliver to the adjacent room.
WL550 protective shield compatible
The WL550 is the model-specific protective shield for the PRO 20, PRO 20 SL, and PRO 20 Duo. It mounts around the stove and reduces safety distances to combustible materials further than the stove's standard 4" side and back clearances. For sauna rooms where maximising bench area is a priority, the WL550 provides additional installation flexibility. Sold separately at BathingBrands.
Pro Series platform - multiple configurations
The WKPR20SLM is the exterior-feed SL variant of the Pro 20 platform. The same 24.1kW platform is also available as: standard interior feed (PRO 20, WKPR20M), with built-in 20L front water tank (PRO 20 ES), with built-in 30L left-side water tank (PRO 20 LS), and as a dual-room sauna-plus-fireplace combination (PRO 20 Duo). All share the 283-706 cu ft range, 88-lb stone requirement, and WL550 shield compatibility. Designed and made in Finland by Harvia. We are an authorized Harvia dealer.
About Harvia
Made in Finland - CE Certified - Pro Series SL
Harvia PRO 20 SL. 24.1kW. 283-706 cu ft. Exterior feed. Fireplace view in adjacent room.
Harvia is a Finnish sauna and spa company established in 1950. The PRO 20 SL is the exterior-feed variant of Harvia's 24.1kW Pro Series stove - a through-wall fire chamber that lets one person load wood from an adjacent room while another enjoys the sauna inside, with the cast-iron glass door providing a fireplace view in the adjacent room. 88 lbs of AC3020 stones (2 boxes) and a 6" North American flue adapter are required and sold separately. Pallet delivery. We are an authorized Harvia dealer.
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24.1kW wood-burning - 283-706 cu ft - no electricity required
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SL exterior feed - wood from adjacent room - fireplace view outside sauna
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Cast-iron glass door - reversible direction - vigorous bathing performance
- Safety distances: 4" sides, 4" back, 12" front
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88 lbs AC3020 stones (2 boxes) required - 6" adapter required - both sold separately
PRO 20 SL vs PRO 20 vs Legend 240 SL - exterior feed stoves compared
PRO 20 SL vs PRO 20 vs Legend 240 SL - exterior feed stove selection
Three exterior-feed configurations are relevant for buyers considering the PRO 20 SL. PRO 20 WKPR20M: same platform, interior feed - choose if loading from inside the sauna is acceptable and the fireplace view in an adjacent room is not a goal. PRO 20 SL WKPR20SLM (this listing): 24.1kW, 283-706 cu ft, exterior feed, fireplace view in adjacent room, 88 lbs stones (2 boxes AC3020), tight 4" side clearances. Legend 240 SL WKLE20SLM: 21kW, 353-848 cu ft, exterior feed, reversible cast-iron glass door, 440 lbs stones (10 boxes AC3020). Choose PRO 20 SL for vigorous bathing in the 283-706 cu ft range with a lighter stone requirement and tight safety clearances. Choose Legend 240 SL for the 353-848 cu ft large room range with maximum stone mass (440 lbs) and longer sustained heat after the fire dies down.
Manuals and Documents
Warranty
2-year limited warranty (consumer use)
The Harvia PRO 20 SL is covered by Harvia's 2-year limited warranty from the date of purchase for consumer use. The warranty covers defects in manufacturing and materials under normal use conditions. The warranty does not cover damage caused by improper installation, use of incorrect stone type or size, operating without the required stone load, failure to follow the installation and operating guidelines in the manual, damage from inadequate chimney maintenance, or soot fires. A licensed or certified chimney professional is recommended for all flue installation and regular chimney sweep maintenance. Proof of purchase from an authorized Harvia dealer is required for warranty claims. We are an authorized Harvia dealer.
