Cathelco HEM have developed a new domestic hot water system for luxury yachts which is space saving whilst having the ability to produce hot water at a much faster rate than conventional systems.

“The system is available as a flexible package which can be installed on luxury yachts according to their specific requirements”, said Chris Bell, general manager of Cathelco HEM.

A key factor in the design was producing a system which would ‘regenerate’ hot water very quickly – an essential feature when it has to serve multiple showers, together with galley, laundry and other on-board domestic requirements.

In conventional hot water systems, the heating elements are in direct contact with the water passing through the system which limits the volume of water which can be heated over a short period of time. Therefore, more cylinders are required to store a higher volume of water.

The solution developed by Cathelco HEM is to have a cylinder which heats the water ‘indirectly’ using a tank within a tank. In this way, the inner tank is completely surrounded by a jacket of hot water which raises the temperature of the cold feed very quickly.

“The advantage of this heat exchanger system is that the cylinders can be much smaller, whilst producing large volumes of hot water on a continuous basis”, Mr Bell explained.

One of the problems with conventional ‘direct’ heating systems is the amount of scale that is produced in the cylinder, mainly on the heating elements themselves. This reduces the efficiency of the system, increasing maintenance time as well as causing annoyances such as blocked shower heads and taps.
These problems are eliminated in the Cathelco HEM system because the elements heat up the primary circuit which contains non-corrosive and non-scaling water. As the water never comes into contact with the secondary water, there is no build-up of scale and the need for maintenance is significantly reduced.

Other practical considerations in the retrofit market are that all of the components including the cylinders must be capable of passing through standard hatches. They can also be readily available as spares if the need arises.

“Basically, we are using a small cylinder to produce a greater percentage of heat. As an example, a 263 litre cylinder will continuously deliver over 1,000 litres of hot water per hour”, said Mr Bell. “The equipment is easily scaled to larger vessels by using boilers and cylinders in tandem, so it is a very versatile system based on efficiency and reliability”, he added.

The first system has been installed on the Mary-Jean II, a 62 metre yacht which was built in 2010 by Italian shipbuilder ISA.

“We were already considering ‘tank within a tank’ technology for improving the hot water system on the Mary-Jean II. When we approached Cathelco HEM and discovered that they were developing a system of this type it seemed like the ideal solution. With our old system four cylinders were required to produce hot water, but with the new system there are only two which makes the operation and maintenance of the system much easier. Moreover the recovery time is much faster than our previous boilers. We have an option to ‘hot fill’ the jacuzzi and now we barely notice after we’ve done it. Previously it was a 30 minute plus recovery time”, said Tom Cumming, chief engineer of the Mary-Jean II.