Available on every continent, the wide range of ACV products fulfil the requirements of hot water production, in both private and professional applications.

Hardman House

Liverpool - United Kingdom

Energy efficient hot water supply for Hardman House

Hardman House is a new build student accommodation in Liverpool city centre which caters to students from the University of Liverpool and Liverpool John Moores University Mount Pleasant Campus. Specifiers and installers Carpenter Build Ltd were tasked with finding a product to meet the hot water requirements of the 126 apartments comprising options of two and four bedrooms with ensuites as well as studios. Hot water specialist ACV provided the solution.

Two HM120 and two HM85 ACV HeatMaster® combination boilers plus two HR1000 cylinders were chosen to provide hot water to the building. Both HeatMaster models benefit from a 10-year warranty on the heat exchanger for peace of mind. The units operate in their most efficient (condensing) mode when providing heating and hot water with an energy rating of A for both. Water reheats within 30/36 minutes from 40 to 87°C (HM120/HM85). Due to the stainless steel tank, they do not require anode protection to prevent corrosion and are low maintenance. As water is stored above 60°C, it also provides protection against Legionella bacteria. The HM120 can deliver a continuous flow of 3,402 litres per hour, whereas the HM85 provides a continuous flow of 2,534 l/h at a temperature of 40°C.

Benefiting from tank-in-tank technology

The HeatMaster contains a stainless steel vessel within the outer tank (tank-in-tank). In this boiler, the tank is ring-shaped with the flue pipes running through its centre. The stainless steel tank holds a limited volume of water to meet short-term demand. The wall of the inner tank becomes an indirect heat exchanger for DHW generation.

While the outer tank contains the (hot) primary water, the inner tank stores domestic hot water (DHW). The heat transfer from primary water to DHW then takes place on the wall of the inner tank. Due to its corrugated nature, the surface area is increased which produces excellent heat transfer, resulting in an exceptionally fast recovery time. This allows water to be stored at higher temperatures (80°C) and also reduces the required vessel size to supply a building.

In hot water draw-off mode, a domestic water thermostat senses the introduction of cold water to the tank and cuts off the heating pump in order to save all the boiler’s output for heating. Owing to the large heat exchange surface area, the tank absorbs the generated heat from the burner to gradually warm up the water as it enters the tank.

Thanks to the short recovery time less hot water is required to reach the desired output temperature when it is mixed with cold water. Heat losses are also minimised, as the DHW in the inner vessel is surrounded by hot primary water, lowering energy wastage.

Another aspect is protection from Legionella bacteria. These are found in natural and man-made water systems and cause a range of illnesses, including Legionnaires’ disease, a potentially fatal form of pneumonia. Legionella bacteria multiply rapidly where nutrients are available and water temperatures are between 20-45°C. As the bacteria do not survive above 60°C, HSE advises that water heaters should store water at 60°C or higher and distributed at 50°C or higher. Their growth can effectively be prevented with the Tank-in-Tank system due to the high temperature hot water storage.

Suitable for hard water areas

When domestic hot water is drawn off the HeatMaster, a brief underpressure in the tank is created, followed by a slight overpressure when the draw-off tap is closed again. As the inner tank is free to move, its walls expand and contract slightly under the influence of these pressure changes which effectively prevents the formation of limescale on the heat exchanger surface. The effectiveness of this feature has not only been confirmed through thorough testing but also testimonials from customers based in hard water areas. ACV’s Tank-in-Tank water heaters effectively prevent the formation of limescale deposits as opposed to traditional coil systems which require frequent descaling. For this reason, the heat transfer efficiency and hot water output of the products with this technology remain high throughout the service life of the installation.


Supporting the direct fired water heaters

Two indirect fired HR1000 stainless steel cylinders with a capacity of 1000L for domestic hot water production were also installed which are directly heated via the HeatMaster boilers to supplement hot water production.

 On his choice, Mike Ingram from Carpenter Build who installed the combi boilers, commented,

“We’ve chosen them for various reasons. The hot water demand is split between the differently sized apartments (studio/2- and 4-bedroom ensuites) which determined the volume requirement. The units have great recovery rates, the same goes for the energy performance. Thanks to the tank-in-tank principle we can also save on installation materials and plant room space which our client The University of Liverpool also appreciates. Lastly, it’s very important to us to have a self-contained unit for space-saving, ease of servicing and maintenance. We’ve used the HeatMaster in eight of our previous schemes which comprise of more student accommodation but also in a Grade II listed project for a small private rented sector refurbishment. It is a reliable design and we have very little problems, so the model is maintenance and trouble free. ACV has provided good ongoing support and technical assistance throughout the project. We’ve already discussed projects leading into the near future.”

Hardman House was opened in September 2019, is fully booked with no complaints of hot water running out even during peak periods which proves the design is working well.