The HUUM STEEL 9.0STU Package is a complete sauna heater package for rooms from 318 to 530 cubic feet, including the STEEL 9kW floor-standing heater, UKU sauna control (Local Black or WiFi - selected at checkout), and 330 lbs of rounded olivine diabase sauna stones. The STEEL 9 steps up from the STEEL 6 with 50% more output for the same slender stainless steel tower body and the same 330-lb stone capacity, extending coverage into the 318-530 cu ft room range on a single 50A / 8 AWG circuit. No UKU Extension Box is required. The STEEL 9 is the correct choice for buyers in the 318-530 cu ft range who want a floor-standing slender stainless steel tower with 330 lbs of stone mass, minimal 4" (10 cm) wall clearances, and an integrated air duct - on a single electrical circuit without dual-circuit complexity.
STEEL 9 vs STEEL 6 - same body, more output, heavier circuit
The STEEL 6 and STEEL 9 share identical body dimensions - the same slim rectangular stainless steel tower profile, the same 330-lb stone capacity, and the same integrated internal air duct. What changes is output level, room range, and electrical specification. The STEEL 6 covers 177-318 cu ft on a single 30A / 10 AWG circuit with 2" (5 cm) wall clearances. The STEEL 9 covers 318-530 cu ft on a single 50A / 8 AWG circuit with 4" (10 cm) wall clearances - slightly more than the 6kW model due to the higher output level, but still exceptionally minimal for a 9kW floor-standing heater. For rooms from 318 to 530 cu ft where a single-circuit 50A installation is available, the STEEL 9 is the directly matched output level. No dual-circuit wiring is needed, and no UKU Extension Box is required.
318-530 cu ft - mid-size sauna rooms in the STEEL tower form
The 9kW room range covers mid-size dedicated home sauna rooms, two-bench sauna cabins, and smaller commercial installations. At this range, the STEEL 9's floor-standing format and minimal 4" clearances are especially valuable in sauna rooms where bench positions leave limited space between the heater location and the walls - a common constraint in purpose-built sauna cabins where the bench wraps around three walls and the heater must fit into a corner or end position without violating safety distances. The STEEL's slim rectangular profile takes up less floor space than round floor-standing heaters like the HIVE Mini, and its 4" wall clearance at 9kW is far less than the safety distances required by most comparable heaters at this output level.
330 lbs of stone, integrated air duct - the STEEL's consistent specification
Like the STEEL 6, the STEEL 9 carries 330 lbs of rounded olivine diabase stones in 2"-4" (5-10 cm) size - the correct specification for the STEEL basket geometry. All 10 boxes of stones included in this package are the right type and quantity for the STEEL 9. The integrated internal air duct reduces heat-up time by approximately 25% and extends element life by improving airflow through the stone mass during warm-up. The UKU Local Black control is included as standard; UKU WiFi is available at checkout for HUUM app remote preheat and scheduling on iOS and Android. The STEEL 9 does not require the UKU Extension Box - that component is only needed for the STEEL 10.5kW model.
Complete 9kW floor-standing sauna heater package for rooms from 318 to 530 cubic feet. Includes STEEL 9kW heater, UKU control (Local Black or WiFi - select at checkout), and 330 lbs of rounded olivine diabase stones (10 boxes). Same slim stainless steel tower body as STEEL 6 and 10.5 - 330 lbs stone capacity across all three. 4" safety clearance from walls at 9kW. Integrated internal air duct - 25% faster heat-up, extended element life. No UKU Extension Box required. Single 50A breaker, 8 AWG wire. 240V / 1-phase. Adjustable legs. Bench-embedding possible. Max 230°F. SGS Listed. 5-year warranty (elements excluded). Made in Estonia by HUUM.
Complete package - control + 330 lbs stones included 9 kW 318 to 530 cu ft Slim stainless steel tower - same body as STEEL 6 and 10.5 4" safety clearance from walls 330 lb stone capacity - 10 boxes included Integrated air duct - 25% faster heat-up No UKU Extension Box required UKU Local Black or UKU WiFi - select at checkout HUUM app - iOS and Android (WiFi variant) Single 50A breaker - 8 AWG - 240V 1-phase SGS Listed - made in Estonia 5-year warranty (elements excluded)
Specifications
Electrical
| Power output |
9 kW |
| Voltage |
240V / 1-phase / 60 Hz |
| Amperage draw |
37.5 A |
| Circuit breaker required |
Single 50A (standard 2-pole - no GFI/GFCI) |
| Wire gauge |
8 AWG |
| UKU Extension Box required |
No - not required for 9kW |
| Certification |
SGS Listed |
Room sizing and stones
| Room volume |
318 to 530 cu ft |
| Stone capacity |
330 lbs (150 kg) |
| Stones included |
Yes - 10 boxes rounded olivine diabase |
| Stone size |
2" to 4" (5-10 cm) rounded |
| Max temperature |
230°F (110°C) |
Physical and clearances
| Profile |
Slim rectangular stainless steel tower |
| Safety clearance from walls |
4" (10 cm) at 9kW |
| Mounting |
Floor-standing with adjustable legs |
| Bench-embedding |
Possible - embedding flange sold separately |
| Air duct |
Integrated internal - 25% faster heat-up |
| Construction |
Brushed stainless steel |
| Origin |
Made in Estonia by HUUM |
Control options - select at checkout
| UKU Local Black |
Wall-mounted digital control - on-site operation |
| UKU WiFi |
Adds HUUM app remote preheat and scheduling |
| App |
HUUM app - iOS and Android (WiFi variant) |
| UKU Extension Box |
Not required for 9kW |
STEEL series comparison
| STEEL 6kW |
177-318 cu ft | 30A / 10 AWG | 2" clearance | No ext box |
| STEEL 9kW (this listing) |
318-530 cu ft | 50A / 8 AWG | 4" clearance | No ext box |
| STEEL 10.5kW |
353-706 cu ft | 50A / 8 AWG | 4" clearance | Ext box required |
| Body dimensions |
Identical across all three STEEL models |
| Stone capacity |
330 lbs - identical across all three |
Warranty
| Warranty period |
5 years (elements excluded) |
| Design |
Slim brushed stainless steel tower |
What's included
HUUM STEEL 9kW floor-standing sauna heater - brushed stainless steel tower
UKU sauna control (Local Black or WiFi - selected at checkout)
Rounded olivine diabase sauna stones - 10 boxes (330 lbs)
Adjustable legs
Installation and operation manual
Optional accessories (sold separately): HUUM STEEL safety railing (recommended), STEEL embedding flange (for bench mounting), reflector panels (reduce wall clearances further). A licensed electrician is required for all electrical connections.
Why the HUUM STEEL 9.0STU Package stands out
330 lbs of stone for 318-530 cu ft rooms
The STEEL 9 delivers 330 lbs of rounded olivine diabase stone mass for rooms from 318 to 530 cubic feet - the same stone capacity as the STEEL 6 for a meaningfully larger room range. More stone mass relative to output means softer, sustained steam and consistent bathing temperature through the session. For rooms in this range, the STEEL 9 is the maximum stone mass available without stepping up to a dual-circuit installation.
4" from walls - fits tight sauna layouts
The STEEL 9 requires only 4" (10 cm) safety clearance from surrounding walls - minimal for a 9kW floor-standing heater. In sauna rooms where bench positions or structural constraints limit the available space around the heater position, the STEEL's slim rectangular profile and small clearances allow placement that wider or more projecting heaters at this output level cannot achieve.
Same body as STEEL 6 and 10.5
The STEEL 9 is physically identical to the STEEL 6 and STEEL 10.5 - same slim stainless tower profile, same 330-lb stone capacity, same adjustable legs, same embedded flange compatibility. The heater footprint and installation procedure are the same regardless of output level within the STEEL floor-standing series. More output for a larger room does not mean a larger heater.
Single circuit - no extension box
The STEEL 9kW operates on a single 50A / 8 AWG circuit with no UKU Extension Box. A single-circuit installation is simpler to plan and wire than the dual-circuit configuration of the HIVE 12kW and above. The UKU Extension Box is only required for the STEEL 10.5kW. For rooms from 318-530 cu ft, the STEEL 9 achieves full output on a single standard electrical circuit.
Integrated air duct - 25% faster heat-up
The integrated internal air duct reduces heat-up time by approximately 25% and extends element life. For a 318-530 cu ft room at 9kW, the time saving is meaningful - particularly for regular sauna users and light commercial installations where session frequency makes warm-up time a practical consideration. Elements also last longer when airflow is optimised through the stone mass from the start of each cycle.
UKU WiFi - remote preheat for a mid-size sauna
A 318-530 cu ft room at 9kW takes 30-45 minutes to reach bathing temperature. Upgrading to UKU WiFi at checkout adds HUUM app control - start the preheat before leaving work, set a recurring weekly schedule, and monitor temperature remotely. No extension box is required. The WiFi upgrade connects directly to the UKU control without additional hardware for the 9kW model.
About HUUM
Made in Estonia - SGS Listed
HUUM STEEL 9STU. 9kW. 318-530 cu ft. 330 lbs of stone. Slim tower. 4" from the wall. Single 50A circuit.
HUUM is an Estonian sauna heater company. The STEEL 9STU Package steps up from the STEEL 6 with 50% more output in the same slim stainless tower body for rooms from 318 to 530 cubic feet. The package includes the STEEL 9kW heater with integrated air duct, the UKU control (Local Black or WiFi at checkout), and 10 boxes of rounded olivine diabase stones (330 lbs). No UKU Extension Box required. Single 50A / 8 AWG circuit. 4" safety clearance from walls. We are an authorized HUUM dealer.
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Complete package - STEEL 9kW, UKU control, and 330 lbs rounded olivine stones
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9kW, 318-530 cu ft - single 50A / 8 AWG, 240V/1PH
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Same slim tower body as STEEL 6 and 10.5 - 330 lbs stone capacity
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No UKU Extension Box required - single-circuit installation
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4" from walls - 5-year warranty (elements excluded)
STEEL 6 vs 9 vs 10.5 - choosing the right output
Which STEEL floor-standing model is right - 6kW, 9kW, or 10.5kW?
All three floor-standing STEEL models share the same slim stainless tower, 330-lb stone capacity, integrated air duct, and adjustable legs. STEEL 6kW: 177-318 cu ft, single 30A / 10 AWG, 2" wall clearance, no extension box. STEEL 9kW: 318-530 cu ft, single 50A / 8 AWG, 4" wall clearance, no extension box. STEEL 10.5kW: 353-706 cu ft, single 50A / 8 AWG, 4" wall clearance, UKU Extension Box required (included in that package). The 9 and 10.5 share the same electrical specification - the difference between them is room size and the extension box requirement. For rooms below 354 cu ft with standard insulation, the 9kW is the correct and more efficiently sized choice. For rooms from 531-706 cu ft or rooms with significant cold surfaces pushing adjusted footage above 530, the 10.5kW is required. A licensed electrician is required for all installations. No GFI/GFCI. STEEL safety railing recommended.
Manuals and Documents
Warranty
5-year limited warranty (elements excluded)
The HUUM STEEL 9.0STU Package is covered by HUUM's 5-year limited warranty from the date of purchase. The warranty covers defects in manufacturing and materials under normal use conditions. Heating elements are excluded from the 5-year coverage and carry their own separate warranty period. The warranty does not cover damage caused by improper installation, use of incorrect or non-approved stones, operating the heater without the required stone load, or failure to follow HUUM's installation and operating guidelines. A licensed electrician is required for all electrical connections. Do not connect to a GFI/GFCI breaker. Proof of purchase from an authorized HUUM dealer is required. We are an authorized HUUM dealer.
