Water heaters and calorifers

Yes, Hamworthy Heating offer a wide range of water heaters, plus calorifiers and storage tanks. The range includes the Dorchester DR-SG condensing water heater, Dorchester DR-FC Evo condensing water heater, DR-CC condensing water heater, Halstock calorifier, Halstock storage tank, Powerstock hot water storage tank and Powerstock calorifier. For more information on the individual ranges visit HERE.

Unvented hot water systems require specific components to ensure they run safely and efficiently and meet the legal safety requirements laid out in Building Regulations Approved Document G, section 3. Manufacturers offer unvented kits which contain the necessary components for installation according to Building Regulations which have been appropriately sized according to the technical characteristics of the water heater or calorifier.

Yes, Hamworthy Heating can provide unvented kits for the full range of water heater products – calorifiers and direct fired water heaters. The kit contents and specification of individual components can be different depending on the product range, but generally include:

• Strainer

• Pressure control valve

• Balanced cold supply connection

• Non-return valve

• Expansion relief valve

• Expansion vessel connection

• Expansion vessel appropriately sized

• Temperature pressure relief valve

• Tundish

For more information on unvented kits, refer to the product brochures HERE.

Expansion vessels are essential in any pressurised heating system and are likely to be present in an unvented hot water system. Without an appropriately sized expansion vessel the components of a closed water system are at risk of becoming damaged by changes in pressure. Expansion vessels - also known as hydraulic accumulators or expansion tanks – are usually located in or near the boiler/water heater but this will depend on system design. Expansion vessels can be sized either for the individual product or sized for the total amount of expansion volume required, if there are multiple hot water products installed together.

Expansion vessels contain air or an inert gas such as nitrogen – as well as water from the system - separated by a membrane that is either a rubber bag or bladder, or a rubber sheet or diaphragm. Water in the expansion vessel expands as the cold, pressurised mains water is heated. As it does, the air within the vessel is compressed to absorb the increased volume, managing the impact of the pressure increase. As the water cools, its volume decreases, and the water level drops again.

Flow through vessels have been specifically developed to reduce the risk of stagnation and contamination from slow moving water. They do this by keeping water moving through the expansion vessel using a Flowjet valve. Hamworthy Heating can provide standalone flow through expansion vessels and a Flowjet valve that diverts part of the water flow in the system into the vessel, preventing water stagnation and guarding against the breeding of harmful bacteria – most notably legionella (which causes the potentially fatal Legionnaires disease).The Flowjet valve also allows for expansion vessels to be drained, bypassed or isolated during removal or replacement. The flow through expansion vessel from Hamworthy Heating also has an internal bladder manufactured in Butyl rubber to limit the risk of bacteria growth, which makes it particularly suited to healthcare premises.

A flow through expansion vessel reduces the risk of legionella growth in an unvented system as the design of the vessel and valve keep water moving, reduces the amount of pipework in the system and gives more flexibility for maintenance and replacement.

When a hot water system is running as usual, the expansion vessel will regularly partially empty and then refill, exchanging water with the system. However, expansion vessels are known to be points that run the risk of bacterial growth as they can suffer from low flow rates or stagnant water. This is particularly true if the system is unused, or the pressure and temperature remain steady over a period of time. In that case the normal fill and replace cycle won’t be naturally changing the water and bacteria can flourish.

Yes, in hard water areas, limescale occurs when water is heated and excess minerals in the water accumulate and become drawn to the hottest point, which is often the tank surface and the heat exchanger. Carbon dioxide and calcium within water combine to form calcium hydrogen carbonate. When heat is applied to water, the composition breaks down and the insoluble calcium carbonate (CaCO₃) forms scale deposits on heat exchangers and tank surfaces.

With the scale acting as an insulator, more heat is required to permeate the scale and heat the water. As a result, heat-up times lengthen, recovery times increase, and more energy is used for the same output. With approximately every 1mm of scale reducing efficiency by 7–10%, this is an important consideration in terms of running costs. Moreover, as the metal underneath the scale eventually starts to corrode due to the increasingly acidic conditions, a breakdown could occur. For more information on water heater maintenance, sign up for our CIBSE approved CPD on ‘Best Practise in Domestic Hot Water’ HERE.

Limescale comes from the remnants of dissolved minerals such as calcium carbonate, magnesium or gypsum present in our water supply. When it rains, the water filters through limestone and chalk and collects in an underground layer called an aquifer. Despite the extensive filtration process performed by water suppliers, these dissolved minerals can still end up in water and depending on geographical location, can affect the performance of boilers, heaters and water heaters. For more information on water composition visit HERE.

The hardness of water is measured in parts per million (ppm) of calcium carbonate deposits. This is caused by the geology of the region. Very hard water is >200 ppm. Hard water forms when water passes through limestone and chalk in the ground which are full of calcium and magnesium carbonates. In comparison, soft water areas generally have < 100ppm. Soft water comes from areas across the country that are formed of hard igneous rock, like granite that rainwater runs over. Scotland, Southwest and Northwest England, and West of Wales are typically soft water areas. Soft water is pure and has low electrical conductivity. Water composition will ultimately have an impact on product material and additional protective measures.

There are many limescale protection devices on the market. While stainless steel products provide a durable first line of defence, it is important to note that stainless steel offers more protection against corrosion caused by soft water rather than preventing limescale entirely. Stainless steel products can still scale up.

However, the Hamworthy Heating range of stainless steel hot water cylinders and condensing water heaters – such as the Dorchester DR-CC and Halstock stainless steel calorifier – are constructed from high grade 316L austenitic stainless steel, do not require anode protection, and are designed to reduce maintenance and increase system lifespan. For more information visit HERE.

When it comes to tackling the different issues commonly associated with water composition and DHW systems, the biggest advantage of utilising stainless steel is its durability. Also, as no lining needs to be applied to the inside of a stainless steel vessel, this reduces the risk of imperfections and small crevices from appearing, which can cause water to become stagnant and corrode over time. Offering relatively low maintenance, their smooth surface also makes them easy to clean, which can help to minimise the risk of scale build-up and sediment accumulation. Lastly, from a practical point of view, stainless steel products have the added advantage of being lighter in weight, which makes them easier to transport, handle and install. For more information on the benefits of stainless steel visit HERE.