🧖 Harvia Hidden Heater HH6 6kW Steel Sauna Heater – 6-10 m³ Capacity

Innovative Concealed Design for Seamless, Space-Saving Sauna Heating

♨️ Product Overview

The Harvia Hidden Heater HH6 6kW Steel represents a revolutionary approach to sauna heating, designed specifically for installations where aesthetics and space efficiency are paramount. This ingenious Finnish-engineered heater mounts discreetly behind sauna benches, delivering powerful and even heat distribution while remaining completely out of sight.

Crafted from premium stainless steel, the Hidden Heater HH6 combines Harvia’s renowned manufacturing excellence with practical innovation. Ideal for community saunas, spa facilities, and discerning home installations, this 6kW powerhouse efficiently heats sauna rooms between 6 and 10 cubic metres whilst maximising your available space.

The concealed installation design not only creates clean, uncluttered sauna interiors but also enhances safety by eliminating direct contact with hot surfaces. With over 75 years of Finnish sauna expertise behind it, the Hidden Heater represents Harvia’s commitment to combining tradition with innovation.

⭐ Key Features

• ✅ Concealed Installation Design – Mounts behind sauna benches for a clean, modern aesthetic and maximised floor space
• ✅ Premium Stainless Steel Construction – Durable, corrosion-resistant body built for demanding commercial and residential use
• ✅ 6kW Power Output – Efficiently heats sauna rooms from 6 to 10 m³ to optimal bathing temperature
• ✅ 15kg Stone Capacity – Generous stone reservoir for excellent steam generation and heat retention
• ✅ IPX4 Splash-Proof Rating – Designed for the demanding wet environment of authentic sauna use
• ✅ CE Certified – Meets all European safety and quality standards for peace of mind
• ✅ Optional Water Delivery System – Compatible with soapstone bowl and flexible hose for controlled löyly (steam)
• ✅ External Control Unit Operation – Separate control panel allows precise temperature management from outside the sauna
• ✅ Professional-Grade Durability – Built for heavy-duty commercial use with extended operational life
• ✅ Finnish Engineering Excellence – Designed and manufactured by Harvia, the world’s leading sauna brand

🔧 Technical Specifications

Specification	Value
Power Rating	6.0 kW
Voltage	400V 3-phase (3N~)
Fuse Size	3 × 10 A
Connection Cable	5 × 1.5 mm² (H07RN-F recommended)
Room Capacity	6 – 10 m³
Dimensions (H × W × D)	830 × 1175 × 255 mm
Net Weight	33 kg
Gross Weight (Packaged)	34.5 kg
Stone Capacity	15 kg (maximum)
Recommended Stone Size	Ø 5-10 cm
Installation Type	Wall-mounted (concealed behind benches)
Control Type	Requires separate external control unit
IP Rating	IPX4 (splash-proof)
Electrical Frequency	50/60 Hz
Material	Stainless Steel
Certifications	CE, EAC
Product Code	HH060400
Type Code	HH6

📏 Room Sizing Guide

Basic Sizing Formula:

1 kW = approximately 1 - 1.5 m³ sauna room volume

This 6kW heater is optimally sized for rooms between 6 and 10 m³.

Adjustment Factors for Accurate Sizing:

Condition	Adjustment
Glass door or windows	Add 1.5 m³ per m² of glass surface
Uninsulated log walls	Multiply room volume by 1.5
Exposed brick, tile, or concrete surfaces	Add 1.2 m³ per m² of exposed surface
High ceiling (above 2.3m)	Add additional volume accordingly
Outdoor or barrel sauna	Add 25-30% to calculated volume

Worked Example:

📍 Example Room: 2.0m × 1.6m × 2.2m
- Base volume: 7.04 m³
- Glass door (0.7m × 2.0m = 1.4 m²): Add 2.1 m³
- Total calculated: 9.14 m³
- Harvia Hidden Heater HH6 (6kW): ✅ Suitable for 6-10 m³
- Verdict: Ideal match for this room configuration

Important: For best results, ensure minimum sauna room height of 2100 mm as specified by the manufacturer.

💷 Running Costs

Energy Rate Used: £0.245/kWh (UK Ofgem Price Cap, Q4 2024)

Annual Cost Calculation:

Usage Level	Sessions/Week	Hours/Year	Annual Cost
🏠 Light Use	2	150	£220.50
🏠 Regular Use	4	300	£441.00
🧖 Heavy Use	6	450	£661.50

Calculation Formula:

Annual Cost = Power (kW) × Hours per Year × Electricity Rate (£/kWh)

Example (6kW heater, Regular Use):
6 kW × 300 hours × £0.245 = £441.00 per year

Per Session Cost (1.5 hour session):
6 kW × 1.5 hours × £0.245 = £2.21 per session

⚠️ Actual costs depend on your specific tariff, usage patterns, session duration, and current energy rates. The above calculations use the Ofgem price cap rate as a reference point.

⚡ Installation Requirements

Electrical Requirements:

Requirement	Specification
Voltage	400V 3-phase (3N~)
Fuse Rating	3 × 10 A
Cable Size	5 × 1.5 mm²
Cable Type	H07RN-F rubber cable or equivalent
Dedicated Circuit	Required
Junction Box Height	Maximum 500 mm from floor

Installation Opening Requirements:

Dimension	Measurement
Opening Height	Minimum 2000 mm
Opening Width	Minimum 1000 mm
Opening Depth	Minimum 375 mm

Minimum Safety Clearances:

Position	Distance
Front (to combustible materials)	75 mm
Front (to non-combustible materials)	75 mm
Sides (to combustible materials)	80 mm
Sides (to non-combustible materials)	80 mm
To Ceiling	1070 mm (minimum)
Room Height	2100 mm (minimum)

Ventilation Requirements:

• Fresh air intake positioned minimum 500 mm above the heater
• Intake pipe diameter: 50-100 mm
• Exhaust air vent positioned low, opposite the heater
• Exhaust vent cross-section should be twice the intake size
• Air should change approximately 6 times per hour

Partition Wall Requirements:

• Leave 80 mm gap under partition wall in front of heater for air circulation
• Install protective grid over partition wall above heater
• Maintain 10-20 mm gap between grid and ceiling

⚠️ IMPORTANT: Installation must be carried out by a qualified electrician 
in accordance with BS 7671 (IET Wiring Regulations) and local building 
regulations. PVC-insulated cables must NOT be used due to thermal 
degradation risks. All cables above 1000 mm in the sauna must withstand 
temperatures of at least 170°C when loaded.

🛡️ Safety Features & Certifications

Built-in Safety Systems:

• ✅ Overheat protection with automatic safety cut-off
• ✅ Thermal protection sensor in dedicated sensor box
• ✅ External control unit with temperature limiting
• ✅ IPX4 splash-proof rating for wet sauna environments
• ✅ Concealed installation reduces contact burn risk
• ✅ Temperature sensor with 4m cable length for optimal placement

Certifications:

• ✅ CE Marked – European Conformity
• ✅ EAC Certified – Eurasian Conformity
• ✅ IPX4 Rated – Splash-proof protection
• ✅ Designed for professional/commercial use environments

Warranty Information:

• Family/Residential Use: 2 years
• Community/Shared Residential Use: 1 year
• Commercial/Institutional Use: 3 months

🎯 Ideal Applications

Application	Room Size	Typical Capacity	Notes
🏠 Home Sauna	6-8 m³	2-4 people	Perfect for space-conscious residential installations
🧖 Wellness Suite	7-10 m³	3-5 people	Ideal for boutique spa and wellness centres
🏢 Small Commercial Sauna	6-10 m³	4-6 people	Built for demanding public use environments
🏨 Hotel/Resort	6-10 m³	3-5 people	Professional-grade for hospitality settings
🏋️ Gym/Fitness Club	6-10 m³	4-6 people	Heavy-duty construction for high-traffic facilities
💆 Spa Treatment Room	6-8 m³	2-4 people	Discreet design maintains premium aesthetics

🪨 Sauna Stones

• Stone Capacity: 15 kg (maximum)
• Recommended Stone Size: Ø 5-10 cm diameter
• Stones Included: No (sold separately)
• Recommended Stone Types: Peridotite, olivine diabase, olivine, or vulcanite
• Stone Maintenance: Re-arrange at least once annually; replace crumbled stones
• Important: Use only jagged-edge stones designed for sauna heaters; decorative stones void the warranty

Stone Care Guidelines:

• Wash stones before first use to remove dust
• Do not pack stones too tightly; allow air circulation
• Remove stone debris from heater bottom during annual maintenance
• More frequent maintenance required with heavy use

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🎛️ Control Options & Accessories

Control System: The Hidden Heater HH6 requires a separate external control unit (not included). The control unit should be installed outside the sauna room in a dry location at approximately 1700 mm height.

Compatible Control Units:

• Harvia C90 Control Unit
• Harvia C150 Control Unit
• Harvia Xenio CX170 (with additional features)
• Harvia Griffin CG170 (digital control)

Control Features (varies by model):

• Timer: Adjustable with delay start capability (up to 12 hours advance programming)
• Thermostat: Adjustable temperature range (+40°C to +110°C)
• Duration: Programmable sauna duration (1-12 hours)
• Additional functions: Lighting and ventilation control (model dependent)

Optional Accessories:

• Soapstone water bowl (ZHH-220) – For controlled löyly delivery
• Flexible hose pipe – Connects bowl to heater for water delivery
• Wooden plate for water bowl (ZHH-221)
• Protective grid (ZHH-400) – For partition wall installation
• Water channel (ZHH-120)

❓ Frequently Asked Questions

Q: What size sauna room will this heater work for? A: The Harvia Hidden Heater HH6 is designed for sauna rooms between 6 and 10 m³. For rooms with glass doors, uninsulated surfaces, or log walls, add the appropriate adjustment factors to your room volume calculation before selecting a heater.

Q: How long does it take to heat the sauna? A: A well-insulated sauna room will typically reach bathing temperature (65-80°C) in approximately 45-60 minutes. Heat-up time varies based on room insulation, ambient temperature, and starting conditions.

Q: What electrical supply do I need? A: This heater requires a 400V 3-phase (3N~) supply with a dedicated circuit protected by 3 × 10 A fuses. Professional installation by a qualified electrician is mandatory.

Q: Are sauna stones included? A: No, sauna stones are sold separately. You will need approximately 15 kg of quality sauna stones (Ø 5-10 cm). We recommend peridotite, olivine diabase, or vulcanite stones specifically designed for electric sauna heaters.

Q: Is a control unit included? A: No, the Hidden Heater requires a separate external control unit (sold separately). Compatible options include the Harvia C90, C150, Xenio CX170, or Griffin CG170 control units.

Q: What is the warranty period? A: Warranty coverage is 2 years for family/residential use, 1 year for community/shared residential use, and 3 months for commercial/institutional use. The warranty does not cover damage caused by incorrect installation, improper stones, or water quality issues.

Q: Can I install this heater myself? A: No. The electrical installation must be carried out by a qualified electrician in compliance with BS 7671 (IET Wiring Regulations) and local building codes. The 400V 3-phase connection requires professional expertise.

Q: How is water thrown on the stones with a concealed heater? A: Harvia offers optional accessories including a soapstone water bowl and flexible hose pipe system. Water is poured into the bowl on the bench, and the hose delivers it to the heater for controlled steam generation.

📥 Downloads & Resources

📄 Installation & User Manual (PDF) – Complete installation guide with wiring diagrams and maintenance instructions

📄 Technical Datasheet (PDF) – Full specifications, dimensions, and technical drawings

🏆 Why Choose the Harvia Hidden Heater HH6

• ✅ Space-Saving Design – Concealed installation maximises usable sauna space and enables flexible bench arrangements
• ✅ Premium Finnish Quality – Manufactured by Harvia, celebrating 75 years of sauna expertise and global market leadership
• ✅ Enhanced Safety – Hidden placement reduces risk of accidental burns and creates a safer environment for all users
• ✅ Clean Aesthetics – Creates an uncluttered, modern sauna interior that lets the wood and design take centre stage
• ✅ Commercial-Grade Durability – Stainless steel construction built for demanding high-traffic environments
• ✅ Even Heat Distribution – Engineered airflow design delivers consistent, comfortable heat throughout the sauna

🤝 Why Buy from Parts4Tubs

• ✅ UK-based company with local customer support
• ✅ Fast UK delivery from our Northamptonshire warehouse
• ✅ Expert advice from sauna and spa specialists
• ✅ Competitive pricing on genuine Harvia products
• ✅ Full manufacturer warranty support
• ✅ Easy returns within 30 days
• ✅ Secure payment options including card and PayPal

✨ Summary

The Harvia Hidden Heater HH6 6kW Steel delivers innovative concealed heating for sauna rooms from 6 to 10 m³. With its space-saving design, premium stainless steel construction, and 15kg stone capacity, this Finnish-engineered heater provides exceptional performance whilst maintaining clean sauna aesthetics. CE certified and backed by Harvia’s 75-year legacy of excellence, it’s the ideal choice for discerning home owners, spas, and commercial facilities seeking powerful heating without compromising design. Requires separate control unit and 400V 3-phase installation. Order today for fast UK delivery from Parts4Tubs.