Big Book of Hamworthy Products and Services

51 Which product should I choose? This is down to personal preference and how the application is being used. There are pros and cons to using each method and we would always recommend you tailor the system to your project. Some sites even choose a mix of the two methods. The choice is yours, but we are happy to help and advise you which type of system would be most suited to your building. We also provide support in sizing the hot water to ensure you don’t run out or oversize resulting in wasted energy.  Helping you choose the right hot water product for your application Contact your local sales manager for help with sizing your next hot water project. You’ll find their details on the back cover of this guide. What is a direct fired unit? Direct fired units such as our Dorchester water heaters for hot water generation have an integral gas burner that directly heats the water in its storage cylinder. This is done by supplying hot gases through one or more of its heat exchanger fire tubes within the cylinder which then transfers heat to the surrounding water. When using a direct fired unit, the heating and hot water systems are separated. What is an indirect unit? Indirect units such as calorifiers have no integral burner, but contain one or more heat exchanger coils that are filled with hot liquids (water or solar fluid) that have already been heated ‘indirectly’ by one or more external heat source, such as a boiler or solar collectors. When using an indirect fired unit the heating and hot water systems are often integrated. Separation or integration Historically, indirect fired systems had a dedicated hot water boiler used solely for heating a calorifier. But with the high efficiencies of today’s boilers the same boiler can now be used for both the heating circuit and the DHW system. However, when space heating is not required, for example in the summer, the boiler has to operate to provide heat for the hot water system. This can result in wastage of energy if the boiler overfires. This is where the choice of boiler is crucial to be able match the heating load, hot water load and both combined (you can read more about load matching on page 12.) Direct fired water heaters are solely dedicated to the job of hot water generation. They provide a faster heat up and response time compared with an indirect system. An indirect system is in fact ‘heating water to heat water’ and this increases the chance of heat losses in the boiler, and associated pipework between the boiler and calorifier. Direct or indirect 01202 662500 | | Water Heaters & Solar