9kW-18kW

These heaters are designed for large family saunas, health clubs, and commercial spas.

• 9kW: Suitable for 8 to 14 cubic metres.
• 10.5kW - 12kW: Designed for spaces between 10 and 18 cubic metres.
• 15kW - 18kW: Heavy-duty units for large rooms ranging from 14 to 30+ cubic metres.

Note: Always use our Sauna Heater Calculator to get an accurate match, as large glass fronts can drastically reduce the effective heating capacity of these units.

For the vast majority of heaters in this category, yes.

• Above 9kW: Heaters rated 10.5kW, 12kW, 15kW, and 18kW almost exclusively require a 400V Three-Phase supply (red industrial standard). Standard UK single-phase homes cannot support these loads without a significant upgrade from the grid.
• The 9kW Exception: Some 9kW models are "single-phase compatible," but they draw a very high current (approx. 40 Amps). You must check your main fuse rating (usually 60A, 80A, or 100A) to ensure your home has the spare capacity.

Most heaters over 9kW are too powerful to be switched directly by a standard digital control panel.

• The Solution: You will likely need a Relay Box (or Contactor Box). This is a separate power unit installed out of sight (e.g., in a plant room or ceiling void).
• How it works: The slim digital control panel on your wall sends a low-voltage signal to the Contactor Box, which then safely switches the heavy high-voltage power to the heater elements. Many of our kits in this range include this box, but please check the product specification.

• Single-Phase (9kW only): Requires very thick cable (typically 10mm² or 16mm²) to handle the high amperage safely.
• Three-Phase (10.5kW - 18kW): Because the load is split across three phases, the cable can often be thinner (typically 5-core 2.5mm² or 4mm² silicone cable).
• Important: You must always use heat-resistant Silicone Rubber (SiHF) cable for the final connection into the heater itself. Standard PVC cable will melt and is a fire hazard.

Heaters in the 9kW–18kW range are physically larger and require a greater thermal mass to provide consistent heat in big rooms.

• Quantity: Expect to load between 40kg and 80kg of sauna stones depending on the model (floor-standing models often take more).
• Benefit: This large volume of stones produces a softer, radiating heat and allows for substantial "löyly" (steam) when water is ladled on, without cooling the elements down too quickly.
  
  

Yes, this range is built for "heavy-duty" cycles. Commercial heaters often feature armoured heating elements and robust stainless steel chassis to withstand daily operation (12+ hours). If you are installing this in a public gym or spa, ensure you select a model listed for commercial continuous use, as using a domestic model may void the warranty.

Please Note: It is the customer's responsibility to consult a qualified electrician to assess and install the suitable electrical requirements to the heater's specification.

In large saunas, air circulation is vital to prevent "hot spots" and ensure the heater sensors work correctly. You normally require:

1. Low-Level Intake: Directly under or near the heater to feed fresh air into the convection flow.
2. High-Level Exhaust: Located diagonally opposite the heater to pull the hot air across the room.

• Commercial Note: For public saunas, mechanical extraction is often recommended to achieve 6–8 air changes per hour for hygiene.