Difference between internal and external hot tub heater

A wood-fired hot tub and a Jacuzzi are often compared and mixed up. Both wellness products are different. Different in form but also in heating. A jacuzzi is always heated electrically and a hot tub on a wood-fired fire. This can be done either with an internal or external heater. But how does heating with an internal and external stove actually work, and what is the difference?

External stove

The external hot tub heater is located outside the tub. Heat-resistant hoses connect the heater to the hot tub. The external heaters from Welvaere are always double-walled. This means that there is a space inside the stove in which you can fire. But there is also a space filled with the water from the hot tub. When the stove and the hot tub are at the same height this will heat through natural circulation. When the stove is full of water, you can start firing. The cool water enters the stove through the lower hose, is heated and returns to the hot tub through the upper hose. This works naturally because heat always rises to the top. Just like it is warmer in the attic in the summer than it is downstairs.

Internal heater

An internal heater is placed inside a hot tub. When the hot tub is filled with water, most of the heater is under water. The passages in the heater are completely under water and their function is to heat the water. The water that goes into these passages will naturally leave the passageway warm, allowing cold water to be reheated.

Which heater heats water faster?

It is often thought that an internal heater heats the water in the hot tub faster than an external heater. This is because an internal heater sits directly in the water. This is not true, both heaters can heat the water in your hot tub very quickly. The only thing to do with this is the power (kW) of the heater and the number of gallons it needs to heat. For example, it is possible with a 35 kW heater to heat as much as a thousand liters of water to 40 degrees in 1.5 hours!

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