Hot Tub Heat Exchangers

Most hot tubs are supplied with an integral electric water heater, which are usually around 3 kW output, depending on the capacity of the hot tub. This type of heater will usually increase the water temperature by around 1 – 2 °C per hour, so it can take up to 24 hours to heat a tub using ambient temperature water.

To overcome this problem, some users fill their tub with pre-heated (25 °C) water from an adjacent boiler, but given that hot tubs usually operate at around 38-40 °C, it can still take a further 6 to 10 hours to achieve full temperature, depending on the performance of the electric heater.

This long heat up time has created a high level of dissatisfaction for many owners, who want their hot tubs to be available for use much faster than the standard heating system allows.

Consequently, many hot tub users, especially those in the commercial sector, are switching to a new type of heating system, using an external boiler, linked to a Bowman heat exchanger. The benefits include significantly reduced heat up times – typically 3 – 4 hours using ambient temperature water, or 1 hour using pre-heated water), plus significantly reduced energy costs compared to electric heating.

More information on heating hot tubs with Bowman heat exchangers.

Most hot tubs are supplied with an integral electric heater, usually around 3 kW output, depending on the water capacity. However, more recently, there has been a growing trend to use gas heating via an external boiler as this is faster at heating up the water compared to electric. This means when you are not using the hot tub, you can keep it at a lower temperature, or even switch the heating off completely, because it won’t take long to bring it up to the temperature when you are ready to use it.

The main reason is the length of time required to heat a hot tub with an electric heater – typically up to 24 hours, using cold water. To speed things up, some owners ‘pre-fill’ their tub with hot water from a boiler, but even this can require a further 6 to 10 hours of heating to achieve the required 38-40 °C temperature.

Whilst many domestic users were prepared to put up with the inconvenience, commercial users such as holiday parks, could not!

The demand for hot tubs when booking holiday accommodation has risen dramatically and is now the second most requested guest facility. To meet this demand, holiday venues had to find a faster way of heating them, due to guest changeover periods. Typically, there is only around 4-5 hours available to drain, clean, re-fill and heat up a hot tub before new guests arrive.

The solution was relatively simple – use an external heat source such as a gas boiler and simply bypass the hot tub’s electric heater. To enable this, a heat exchanger is required to transfer heat from the boiler water to the hot tub water. It’s exactly the same principle used for most swimming pools, but just on a smaller scale.

Bowman developed an ultra-compact heat exchanger that could be installed in the hot tub’s pipework and the result was hot tubs heated in 3-4 hours using cold water, or in around 1 hour using pre-heated water.

There was also another benefit. Heating hot tubs with electricity can be very expensive. By switching to gas boiler heating, many users reported a significant reduction in the energy costs – some as much as £500.00 per hot tub!

How holiday parks can benefit by switching to gas heating.

More information on Bowman’s hot tub heat exchangers.

Swimming pool heat exchangers work by transferring heat energy from a hot water circuit, to the cooler pool water circuit, without the two fluids ever coming in direct contact with each other.

Most swimming pools are heated via a boiler, using fuels such as Gas, LPG or Biomass, as the energy source. In theory, the most efficient way to heat the pool water circuit would be to connect it directly to the boiler.

Were this to happen, the chemicals and minerals added to the pool water to keep it safe for use, would quickly erode and damage vital components inside the boiler, leading to premature failure and a costly replacement.

However, by using a heat exchanger to act as an ‘interface’ between the boiler water circuit and the pool water circuit, the boiler is protected from damage and the pool water is quickly heated up to the required temperature for use.

Shell and tube design heat exchangers are extremely popular for swimming pools, due to their efficiency and ease of maintenance. Inside the ‘shell’ there is a bundle of tubes, known as the ‘tube core’, through which the pool water passes in a single direction.

At the same time, hot water from the boiler is circulated around the outside of all the tubes in the tube core. Traveling in the opposite direction to the pool water flow, the boiler water transfers its heat to the pool water, before being recirculated back to the boiler, for reheating.

Both water circuits operate in a continuous heating cycle, until the total pool water volume has reached the required temperature, which is usually around 28 – 30 °C.

Bowman manufactures a comprehensive range of swimming pool heat exchangers for everything from spa pools and hot tubs, up to Olympic size pools.

More information on Bowman swimming pool heat exchangers.

As their name suggests, hot tubs require a lot of heat to achieve and maintain the 38°C to 40°C water temperature they usually run at.

Most hot tubs are supplied as standard with an electric heater already installed. This usually takes many hours to heat a typical 1,400 litre hot tub from ambient water temperature to normal operating temperature, and as electricity is one of the most expensive ways of heating, it’s not surprising that many users find their electricity costs rise sharply!

A more efficient solution is to heat the hot tub from an external heat source, such as a gas boiler. Usually, this can be done by connecting pipework from the hot tub to the boiler, in a similar way to adding a new radiator to a new room in a home.

The only difference is the hot tub requires a heat exchanger to act as an interface to keep the pool and the boiler water separate from each other. Installing the heat exchanger into the pool water circuit and connecting to the boiler is straightforward, though a plumber may be required to install.

Once the hot tub is being heated from the house boiler, many users notice how much quicker the water temperature increases and in many cases, the hot tub can be ready to use in just 2 -3 hours of heating, which is a real bonus, as it significantly reduces the energy used and, as gas heating costs are much lower than electricity, energy costs are significantly reduced too!

Bowman has been one of the pioneers in providing hot tub heating via heat exchangers and have a comprehensive range of products for this specific application. For more information on Bowman Hot Tub Heat Exchangers