Yacht Sauna Takes Too Long to Heat Up

If a sauna takes an excessive amount of time to reach the set temperature, it usually indicates that the heater, stones, ventilation, or sensor are not functioning correctly. On yachts, this problem is very common due to salt exposure, vibrations, humidity, and long periods of inactivity. Below we analyze all the main causes and what should be checked.
 

1. Heater undersized for the sauna volume (main issue)

One of the most frequent problems with onboard saunas is an undersized heater compared to the cabin volume. The heater must be properly selected and sized to ensure efficient heating and acceptable warm-up times. For well-insulated cabins without glass walls, the technical guideline recommends 1 m³ of sauna volume ≈ 0.75 kW of heater power.


Example:

For an 8 m³ sauna → heater of approximately 6 kW. If glass panels, heavy walls, or poor insulation are present:

  • the required power increases to 1–1.3 kW per m³.

 

This situation often leads to typical yacht-related issues such as undersized heaters installed by shipyards, saunas taking a long time to reach 60–70°C, and heating elements running at 100% power for extended periods.

 

2. Stones deteriorated, incorrect, or too compact

Sauna stones play a fundamental role in transferring heat inside the cabin. If they are broken, dusty, low-quality, or packed too tightly, the heater struggles to operate efficiently and heating performance is reduced. To avoid these issues, it is important to:

  • replace stones every 6–12 months (especially important on yachts)
  • maintain air gaps between stones and heating elements
  • remove dust and broken stones

 

3. Weakened or partially burnt heating elements

A defective heating element produces less heat, forcing the remaining elements to work at maximum output and slowing the sauna warm-up time. A quick check can help identify the issue: with the sauna off → remove the stones → turn on the heater → all heating elements should glow red.
If one does not glow, it is faulty and must be replaced.
 

4. Temperature sensor reading too high or too low

If the sensor provides incorrect readings, the heater will regulate improperly. The correct sensor position must comply with the following standards:

  • 160 cm (5 ft 3 in) from the floor
  • on the opposite side of the heater
  • free from benches and wooden panels

On yachts, additional issues may arise such as salt-induced oxidation of the sensor, incorrect placement, or cable damage during maintenance operations.


5. Insufficient internal ventilation

If air circulation inside the sauna is inadequate, the heater struggles to distribute heat evenly. Heat accumulates near the ceiling, while the perceived temperature remains low. To ensure proper airflow, it is important to check that the lower air intake is open, the upper air outlet is unobstructed, and no slats or panels block circulation.

 

6. Humidity or condensation inside the sauna cabin

After long periods of inactivity, the sauna cabin may retain a high level of humidity. Cold, damp wood absorbs part of the heat produced by the heater, slowing down the heating process. To solve this issue, it is advisable to turn on the sauna with the door open for about 10 minutes to dry the cabin, then close the door to bring the sauna up to the desired temperature.

 

7. Unstable electrical supply

Onboard yachts, the following conditions are very common:

  • low voltage
  • switching between shore power and generator
  • micro-interruptions
  • non-stabilized generators

When voltage drops, the heater’s effective power decreases → resulting in slower heating.
 

8. Sauna door not closing properly

If even a few millimeters of the sauna door remain open, cold air continuously enters the cabin. This prevents the sauna from reaching the desired temperature and forces the heater to operate unnecessarily for long periods.

 

Normal heating times for yacht saunas

With a properly sized heater and all systems functioning correctly, normal heating times are:

  • 30–45 minutes to reach 70–80°C (158–176°F)
  • 45–60 minutes to reach 90–95°C (194–203°F)

→ Longer times always indicate an underlying issue.
 

When should specialized assistance be requested?

If one or more of the following conditions occur, it is time to contact a qualified professional:

  • the sauna cannot exceed 50–60°C (122–140°F)
  • the heater runs continuously at maximum power without modulation
  • the cabin takes more than one hour to reach temperature
  • uneven heating elements
  • smell of overheating

 

Technical assistance and spare parts for yacht saunas

To ensure proper operation and maximum safety onboard, you can contact Centro Italia Yachting for technical assistance and original spare parts. In Italy, the toll-free number is 800 931 931, while from abroad you can call +39 327 612 0605.