Finnleo Designer-B Sauna Heater

Finnleo Designer-B Sauna Heater

The Finnleo Designer-B electric sauna heater delivers the same deep, even, authentic Finnish heat found throughout the Finnleo lineup, with one defining difference: all controls are built directly into the front of the heater. There's no separate wall-mounted control panel to purchase, wire, or find space for, and no external contactor box required for basic operation — the thermostat and timer live right on the heater itself. This makes the Designer-B the simplest, most cost-effective way to add a self-contained Finnleo heater to a sauna, ideal for installations where a remote control panel isn't wanted, isn't practical, or needs to be avoided to reduce installed cost. The Designer-B series is available in four configurations to match nearly any home, condo, or light-commercial sauna room: 4.5 kW (240V, 1-Phase), 6.0 kW (240V, 1-Phase), 8.0 kW (240V, 1-Phase), and 8.0 kW (208V, 3-Phase) — all sharing the same wall-mounted stainless-steel construction, integrated 9+1 hour timer, and built-in high-limit safety control.

Construction & Design

Every Designer-B heater features a durable, splash-proof stainless-steel enclosure with all conducting parts protected against water exposure, and is safety-listed for permanent residential and light-commercial installations. Each unit mounts to the wall via a heavy-duty steel wall bracket (hardware included) that also maintains the required minimum 2-inch clearance from the wall behind the heater for safe airflow. Control knobs and the electrical terminal box can be relocated during installation — installers can remove the knobs, unsnap the plastic label plates, and reposition the terminal box to the front or either side panel to match bench layout and door swing. A painted trim piece conceals the wiring connections once installed, and the compact wall-mounted footprint maximizes usable floor and bench space compared to floor-standing heaters.

Heating Elements & Rock Chamber

Inside the heating chamber, rocks surround and sit directly above and between the elements so heat radiates evenly through the stone mass rather than blasting directly off bare elements. Rocks are included with every Designer-B heater, sized to the model's output:

• 4.5 kW: three 1,500W elements (240V), rock capacity approximately 45–50 lbs
• 6.0 kW: three 2,000W elements (240V)
• 8.0 kW (1PH or 3PH): three 2,670W elements, combining for a full 8.0 kW output for fast heat-up and strong recovery in larger rooms

Correct rock loading is critical to performance and longevity on every model: smaller rocks go in first around the outer perimeter of the heating chamber, all four sections (front, the two center sections between elements, and back) must be completely filled, outer sections should be packed more tightly with smaller rocks while the center sections are filled loosely to preserve airflow, and all elements must be loosely covered with 2–3 inches of rock above their tops. Rocks smaller than 2" should be discarded and replaced, and a metal rock grate/guard is included and must be installed over the rock bed before use — the heater must never be operated without the rock chamber properly filled and the guard in place.

Integrated Controls & Timer

Because the control is fully built into the heater housing, no separate SaunaLogic2 control or external contactor box is required for basic operation on any Designer-B model, simplifying installation and lowering total system cost. The thermostat knob adjusts bath temperature — turning clockwise raises heat, counter-clockwise lowers it. The built-in timer uses a "9 plus 1" design: turning the dial into the marked 1-hour operating zone starts the heater immediately, while turning it into the "1 to 9" zone delays start-up by up to nine hours, so the sauna is warm and ready exactly when needed with no app or additional low-voltage wiring required. A built-in high-limit control automatically shuts the heater down if room temperature rises to an abnormal level; it is reset by letting the heater cool, turning the timer to zero, and pressing the reset button on the underside of the unit. Finnleo requires that the timer and thermostat never be altered or bypassed, and that an attendant remain present at all times if the sauna is used without the automatic timer engaged.

Room Sizing by Model

• Designer-B 4.5 kW: minimum floor area of 12 sq. ft., volume range of approximately 100–210 cubic feet, wall heights 74"–96"
• Designer-B 6.0 kW: minimum floor area of approximately 21 sq. ft., volume range of approximately 175–425 cubic feet, wall heights 74"–96"
• Designer-B 8.0 kW (1PH or 3PH): minimum floor area of 31 sq. ft., volume range of approximately 250–425 cubic feet, wall heights 74"–96"

Together, the three outputs cover sauna rooms from roughly 100 to 425 cubic feet, letting you match heater capacity precisely to room size rather than oversizing or undersizing the installation.

Electrical Specifications

• 4.5 kW, 240V single-phase: 18.8 amps — minimum 10-2 W/G copper supply wire
• 4.5 kW, 208V single-phase: 21.6 amps — minimum 10-2 W/G copper supply wire
• 6.0 kW, 240V single-phase: 25 amps — minimum 10-2 W/G copper supply wire
• 6.0 kW, 208V single-phase: 28.8 amps — minimum 8-2 W/G copper supply wire
• 6.0 kW, 240V three-phase: 14.4 amps — minimum 12-3 W/G copper supply wire
• 6.0 kW, 208V three-phase: 16.7 amps — minimum 12-3 W/G copper supply wire
• 8.0 kW, 240V single-phase: 33.3 amps — minimum 8-2 W/G copper supply wire
• 8.0 kW, 208V single-phase: 38.5 amps — minimum 8-2 W/G copper supply wire
• 8.0 kW, 240V three-phase: 19.2 amps — minimum 10-3 W/G copper supply wire
• 8.0 kW, 208V three-phase: 22.2 amps — minimum 10-3 W/G copper supply wire

All supply wiring must be copper rated for a minimum of 90°C, sized per Finnleo's official heater specification chart, and installed by a licensed electrician in accordance with the National Electrical Code and local regulations. The heater and controls must be grounded per NEC, any contactor used in the circuit must carry a minimum 250,000-cycle endurance rating, and no electrical outlets or receptacles may be installed inside the sauna room.

Safety & Installation Requirements

• A wooden or metal heater guard rail (fence) is required around every model to prevent bathers from accidentally contacting the heater, positioned per Finnleo's clearance diagrams
• Minimum clearance from the heater to wooden surfaces (benches, side walls, fencing) is 2 inches; supplied mounting brackets maintain proper clearance from the wall behind the heater
• Minimum ceiling clearance above the heater is 44"; benches must never be located directly over the heater
• Two metal safety placards are included with every unit — a CAUTION placard mounted on the interior wall directly above the heater, and a WARNING placard mounted on or beside the sauna door at eye level, both required by code
• Sauna doors must open outward and use only magnetic catches, friction catches, or spring/gravity-loaded closures — never a permanent lock or latch
• No shower and no electrical receptacle may be installed inside the sauna room
• Recommended minimum wall insulation of R-12 in 16" on-center 2x4 stud construction, foil vapor barrier, tongue-and-groove softwood interior paneling, and minimum flooring thickness of 5/8"
• Never apply wood stain, sealant, or preservative to the interior of the sauna room
• Light fixtures run hot during operation and must be positioned away from potential bather contact

Ventilation

Proper sauna ventilation should exchange the room's air approximately six times per hour on every Designer-B model. A fresh-air inlet vent should be located in the sauna wall directly below the heater, with the outlet vent positioned lower than the upper benches, as far from the heater as possible, and roughly two feet higher than the inlet. Vent sizing follows UL Specification 875: for room floor areas under 31 sq. ft., minimum vent opening is 9.3 sq. in.; for areas of 31 sq. ft. or more, minimum vent size equals 0.3 times the floor area in square feet.

Using the Sauna

A typical session involves entering for 10–15 minutes or until perspiration begins, followed by a cool shower and 10–15 minutes of rest, repeated 2–3 times and finished with a brisk cool rinse. Ladle only about half a cup of water onto the rocks at a time to create löyly, and stay clear of the rising steam. Never pour chlorinated pool or spa water onto the heater or rocks, as it can cause corrosion damage. Smoking, exercising, and drinking alcohol inside the sauna room are not recommended.

What's Included

• Finnleo Designer-B sauna heater (4.5 kW, 6.0 kW, or 8.0 kW; 240V single-phase or 208V three-phase per configuration) with integrated front-panel thermostat and 9+1 hour delay timer
• Matched heating elements per model (three 1,500W, three 2,000W, or three 2,670W elements)
• Sauna rocks, sized to heater capacity
• Metal rock grate/guard
• Wall-mounting bracket and mounting hardware
• Built-in high-limit safety control with manual reset button
• CAUTION and WARNING metal safety placards
• Complete installation, operating, and maintenance instructions

Maintenance

Air out the sauna room after each use by leaving the door and vents open, and wash the room down at least weekly with warm water and soap or detergent under daily use. Wipe down the heater periodically with a damp cloth to remove lint and dust. Remove, clean, and inspect the rocks once a year, replacing any that are cracked, crumbled, or smaller than 2". Remove, scrub, and dry duckboard flooring separately from the room floor, and inspect benches and supporting structures annually for dry rot or deterioration, replacing them immediately if damage is found.

Choosing the Right Designer-B

Use the 4.5 kW model for the smallest home saunas and condo installations (100–210 cubic feet), step up to the 6.0 kW for mid-sized rooms (175–425 cubic feet), and choose the 8.0 kW — in single-phase or three-phase, depending on available electrical service — for the largest rooms in the Designer-B range (250–425 cubic feet) or installations where three-phase power is already present. Across every output, the Designer-B's built-in timer and thermostat make it a simple, reliable option for bathers who want straightforward operation without an app or wall-mounted control panel.

Why Buy Finnleo From Us

Finnleo, built by Sauna360 in Cokato, Minnesota, is one of the most trusted names in authentic Finnish sauna. Every heater is safety-tested and listed for North America, with full documentation for code-compliant installation. We are an authorized Finnleo dealer offering full factory warranty, expert sizing help, and support before and after your purchase. Have a question about fit, voltage, or lead time? Reach out and a sauna specialist will help you spec it correctly the first time.