EOS Invisio Midi Under-Bench Sauna Heater | 6 / 9 / 12 kW

You are buying a German heater for an American electrical panel, and that gap is where EOS projects go wrong. The North America Invisio is its own platform: 208V three-phase and 240V variants at 60 Hz, its own installation manual, control boxes, and item numbers. Specs copied from the European 400V catalog will fail your electrician’s first question.

We built a complete United States EOS knowledgebase before we listed a single heater: every current North America item number and UPC, the current US manuals, the room-sizing rules, the full under-bench assembly geometry, and the spare-parts catalog down to individual heating elements. That matters even more here, because the Invisio is a construction detail as much as a product. One example: the Invisio manual’s printed inch conversions contain known misprints (a 1.6 in grill overhang appears as 0.13 in; it is actually about 1.57 in), so we plan every Invisio project from the controlling metric drawing and your builder works from numbers that match the hardware.

• Every variant on this page is a genuine EOS North America SKU with its UPC, sourced through EOS’s official US distribution.
• Your room gets sized against the published EOS floor-area ranges, adjusted for glass, masonry, and ceiling height, not guessed from square footage.
• Your control system, wall-sensor placement, grill and shaft geometry, trough location, service access, and ventilation openings get reviewed with you before anything ships.
• Replacement heating elements and the thermal cutout stay available through us, with EOS part numbers on file.

Call or text (844) 565-1113 with your room dimensions, bench plan, and electrical service and you will get back a configuration that works: heater output, voltage, control kit, and the under-bench assembly math, checked against the current EOS North America documents.

The Invisio Midi is a heater body, not a plug-in appliance, and that is deliberate. The complete system is four parts: the heater, a control panel mounted at eye level outside the cabin, a power box in a dry accessible location outside the hot room, and a digital sensor with a safety limiter (supplied with the control system). Your electronics never sit in 190°F heat.

One Invisio-specific rule: the sensor does not go on the ceiling. It mounts on the cabin wall, centered over the heater, 3.9 inches below the grill, exactly as the Invisio manual draws it, with the heater’s internal limiter wired in series with the cabin limiter.

• EOS Touch 3: a premium 7-inch capacitive color touchscreen with guided setup, clear-text diagnostics, light and fan control, and optional app control through the EOS App Module. Panel-to-power-box cable runs to 32.8 ft maximum.
• EOS EmoTec D: a compact TFT display with a tactile jog dial. Fast, glove-friendly operation.

Panel choice alone does not determine compatibility: capacity, voltage, sensor, cable runs, and firmware all have to line up, so we review every control selection against your heater before fulfillment. EOS has revised its US power-box item numbers across generations; we confirm the exact current kit before your heater ships rather than guessing from an old catalog.

EOS publishes a floor-area range for each output at a 6.2 ft / 6.2 ft reference height. Your real number moves with glass walls, masonry, uninsulated surfaces, and ceilings over 6.2 ft. Size from calculated interior volume and construction, not square footage alone.

A note on the 6 kW: some current EOS web copy stretches its range to 48.4 sq ft. The North America manual and data sheet say 45.2 sq ft, and that is the number we plan to.

Sitting at the top of a range, running a glass front, or planning commercial duty? Send us the room before you commit. You can also plan the full room, under-bench assembly included, in our free 3D tool at SaunaDesignPro.

These are the real EOS North America item numbers, straight from the current US catalog, so your electrician, your builder, and your inspector are all looking at the same SKU.

There is no 12 kW / 240V Invisio Midi in the current EOS North America catalog. If your building has 240V single-phase service, the 9 kW is the largest Invisio we can supply, and we will tell you honestly whether it carries your room.

Full specifications

The heater, dividing wall, grill, bench, trough, sensor, and service access form one engineered assembly with published geometry. Where the manual’s printed inch conversions disagree with the metric drawing, the metric drawing governs; the values below are already corrected.

Front elevation

Side section

Sensor and safety placement: the digital sensor and cabin limiter mount on the cabin wall, centered over the heater, 3.9 in below the grill; the generic EOS ceiling position does not apply. The supplied warning plate mounts near the shaft at eye level. Do not install the Invisio in a generic alcove or under a sloped roof unless an approved design permits it, and keep the heater removable for service without dismantling the cabin: removable bench panels and cable slack are part of the specification.

Ventilation: place the air inlet low in the assembly where fresh air actually reaches the heater, sized to the output table above, and provide at least five cabin air exchanges per hour. The outlet stays open, low on the opposite or diagonal wall. If the heater cannot get enough air despite correct openings, add mechanical assistance.

What arrives, what you add, and what your trades supply, for every Invisio Midi variant:

One catalog note, handled: the EOS accessory list also carries a separate Invisio safety-grill row. Your heater’s required grill is in the factory scope per the current North America manual; we treat the separate row as a replacement/alternate part and verify package contents before shipment on every order.

Inspect all components at delivery, and photograph the cartons before your builder starts.

The Invisio keeps the oldest part of the sauna ritual and simply reroutes it. Stones sit over the elements as in any traditional EOS heater. When you want steam, you pour into the trough; the hose carries the water down to the stainless elbow, and the internal channel distributes it across the hot stones. The steam rises through the grill, and the room responds the way a stone heater should.

Your installer sets the plumbing logic once: trough above the internal channel level, hose running downward without kinks, channel sloping away from the connection. Place the trough where a bather reaches it deliberately but cannot brush it by accident; it gets hot in use, and an optional splash flap can reduce access further. Heat the cabin fully before the first pour, use modest amounts (EOS’s guidance is roughly 0.4 cup per cubic meter of cabin volume, then about ten minutes for the stones to recover), and use only properly diluted sauna essence, never undiluted essence, oils, alcohol, or herbs.

EOS has built sauna equipment in Germany for more than 80 years, and hiding a heater does not exempt it from honest serviceability. The Invisio manual requires that the heater stay accessible for repair without dismantling the cabin, which is why removable bench panels, a planned removal path, and cable slack are part of the specification, and why we review your service access before anything ships. Water and power connections arrange on the left or right, so the serviceable side lands where your bench design wants it.

Every heating element is a published, orderable part: three 2,000 W elements at 6 kW, six 1,500 W at 9 kW, six 2,000 W at 12 kW, plus the 320°F thermal cutout, each with a current 2026 EOS North America part number on file with us.

Wash and loosely restack the stones at least once a year and replace cracked ones. Keep the grill, shaft, and inlet clear, and never let towels or objects into the shaft. If the sauna sits unused for weeks, run it periodically: idle elements can absorb moisture, and the manual describes a supervised drying procedure if a ground-fault device trips after long storage.

Is the control included?

No. Every current EOS US heater pairs with a separate matching control panel and power box: a 9 kW EOS USA control for the 6 and 9 kW Invisio, a 15 kW control (208V 3-Phase) for the 12 kW. Pick Touch 3 or EmoTec D above, or choose the review option and we will confirm compatibility before anything ships.

Can I pour water on a heater I cannot see?

Yes, that is the point of the included infusion set. Pour into the supplied trough and the internal stainless channel distributes the water across the hot stones inside. Use modest amounts and properly diluted sauna essence only, and never pour directly through the grill.

Are the stones included?

No. The current EOS North America catalog lists stones as optional for the Invisio, so they are selected separately (roughly 44-45 lb are required). EOS’s factory documents currently describe the stone size inconsistently, so we confirm the current stone kit and specification with your order.

Is the protective grill included, or an add-on?

Included and mandatory. The current North America manual puts the 48.8-inch grill in the factory scope, fixed between the cabin wall and the top of the dividing wall. The separate grill row in the EOS accessory list is a replacement/alternate part, and we verify package contents before shipment on every order.

Which voltage should I choose: 208V or 240V?

The 6 and 9 kW Invisio Midi come in 240V 2-Line for the single-phase service in most US homes, and in 208V 3-Phase for commercial buildings and many high-rise condos. The 12 kW is 208V three-phase only, sized for commercial rooms and three-phase buildings. Heater, control system, and service must match exactly; send us a photo of your panel and we will confirm before you order.

Can I run a 240V heater on 208V service?

No. Heater, power box, and your electrical service must match exactly. Most US homes have 240V single-phase service; 208V three-phase is common in commercial buildings and some condos. The 12 kW Invisio exists only in 208V three-phase. Not sure which you have? Send us a photo of your panel.

Where do the control panel, power box, and sensor go?

Panel and power box go outside the cabin: the panel at eye level near the door, the power box in a dry accessible location, never inside a sealed cabinet. The sensor is the Invisio exception: it mounts on the cabin wall, centered over the heater, 3.9 inches below the grill, not on the ceiling.

Can it go outdoors, or under any existing bench?

No to both. The North America manual specifies indoor cabins, and the Invisio must sit inside a purpose-built under-bench assembly: dividing wall, shaft, grill, air paths, wall sensor, and removable service access built to the manual dimensions. A generic alcove or an ordinary storage bench does not qualify. Retrofitting an existing sauna? Send us the bench drawings first.

Does hiding the heater make it safer?

Concealment reduces accidental-contact exposure: the hot body sits behind the dividing wall and the grill keeps objects out of the hot-air shaft. But that only holds when the shaft geometry, grill overhang, air paths, sensor position, and service access are built to the manual. The assembly is the safety system; we review it with you before shipping.

What is the lead time?

Invisio heaters ship freight through EOS’s official US distribution. We confirm the current lead time on your exact SKU when you order, and you get tracking when it ships. If timing is critical, call or text before ordering and we will check availability first.

Is it approved for commercial use?

EOS builds the Invisio Midi for private and commercial indoor cabins. Commercial projects get a duty-cycle, ventilation, and control review as part of our quote.

What maintenance does it need?

Wash and loosely restack the stones at least once a year, replace cracked ones, and keep the grill, shaft, vents, trough, and hose clear. Heating elements and the thermal cutout are published EOS spare parts, replaceable by a qualified technician using the planned service access.

What about warranty?

Manufacturer warranty terms apply. Ask us and we will walk you through exactly what applies to your order before you buy.

• EOS Invisio Midi North America data sheet
• EOS Invisio Midi North America installation manual (EN)

These are the current North America documents, not the European 400V versions. The Invisio manual’s printed inch conversions contain known misprints, so the metric drawing governs the assembly geometry. Final circuit sizing always follows the installation manual, the wiring diagram for your exact control kit, your heater nameplate, NEC and local code, and your licensed electrician; the 12 kW model uses multiple 208V feeder circuits into the power box, so never schedule it from a single marketing fuse value.