The heart of the boiler - the heat exchanger We care about the material and construction of our heat exchangers as they’re at the heart of every boiler. But why does the material and design make a difference? We’ll take you through the materials and their qualities below. Which boiler should I choose? This really is dependent on you and your project. What type of building is it? What are the heat loads? What are your environmental objectives? And how will you be looking after your equipment for its life? For unbiased advice and guidance on selecting the best matched boiler for your next project request a free site survey or speak to our in-house technical support team. You have the choice and we can provide a solution. Cast iron Cast iron boilers traditionally dominated the market and have stood the test of time. We launched our first atmospheric cast iron boiler in the 60’s. A cast iron heat exchanger offers great corrosion resistance where system water is poorly treated, making it robust and long-lasting. We back this up with a 10-year heat exchanger warranty on our cast iron boiler. They typically have large waterways enabling them to deal with debris often found in the circuits of old heating systems. Cast iron boilers are not usually suitable for condensing operation due to corrosion. However, our Purewell Variheat mk2 boiler has a secondary heat exchanger to allow it to condense, making it the only ErP compliant cast iron commercial condensing boiler in the UK. Steel shell or shell & tube The higher output boilers often have heat exchangers constructed from pre-fabricated steel shell or shell and tube steel. They are not suitable for condensing except when a secondary heat exchanger is used, as with our Melbury C boiler. They use pressure jet burners and a large single piece boiler design which means you must give careful consideration to access and installation. They also require minimum return temperature control to prevent condensing. Our steel shell power flame products include Ansty, Ensbury, Melbury HE and Melbury C boilers. Stainless steel Heat exchangers manufactured in stainless steel are corrosion resistant to both flue gas and system water. They are durable and long lasting - we offer 5 & 10-year warranties on our stainless steel boilers. Stainless steel is available in many grades and the most common for boilers is 316 which has good welding properties. It also has good heat transfer properties similar to cast iron. Boilers using stainless steel heat exchangers are lightweight and tolerant to a wide pH band of water conditions, typically pH7 to pH10. Our Wessex ModuMax mk3, Stratton mk2 and Varmax boilers all feature a stainless steel heat exchanger. Aluminium alloy Aluminium alloy heat exchangers are often used for modern wall hung condensing boilers as they are lightweight and have good heat transfer capability. It is a low cost metal to purchase and can use high precision die casting for highly efficient, compact sectional heat exchanger design. However, measures must be taken to deal with heating system water quality to prevent galvanic attack and prolong life. The pH band for system water must typically be controlled within pH7 to pH8.5. Aluminium heat exchangers are often designed with small waterways to offer fast response to changing system requirements, but water must be kept clean through use of dirt separation to allow flow through these waterways. The expected life of aluminium boilers is not as long as cast iron or stainless steel. Our Upton boilers feature an aluminium alloy heat exchanger. 01202 662500 | sales@hamworthy-heating.com | hamworthy-heating.com 15 BOILERS
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