What seems like a basic hot water system in many countries around the world is finally catching up in the UK. Unvented hot water cylinders and central heating systems provide hot water at mains pressure level. Unvented systems eliminate cases where two users cannot draw hot water simultaneously, for example when one member of the household having a shower while another tries to do the washing up. Unvented systems use the pressure of the mains infrastructure to retain sufficient pressure of hot water around the entire house. This is in stark contrast to the traditional gravity fed systems with a feeder tank normally positioned in the loft, offering low pressure in the top floors, due to lack of head for the hot water to build up pressure.
In recent decades, typical dwelling designs have evolved remarkably. Many households now have two bathrooms, and many others have a whirlpool bath, multi jet shower or other appliances that use hot water. More so, our hectic lifestyle means we want hot water on demand, without having to wait for it, or having to accept a trickle in the shower. A correctly sized and designed system around an unvented cylinder can provide the perfect solution for all those demands, offering a reliable availability of hot water any time of the day in a sufficient pressure for domestic needs, be it the hot water shower, or the kitchen tap.
Most unvented cylinders are manufactured from metals that fall into one of three categories: copper, stainless steel and glazed sheet metal. Each one of these technologies is highly effective and used throughout the world.
* Copper shell – the price of copper cylinders has risen recently along with the cost of copper in the world commodity markets. Copper shells are very popular in the UK, offering lightweight and relatively reasonable prices. They offer the lowest level of heat retention among the three metals.
* Stainless Steel shell – offers middle ground in terms of heat retention and weight compared to the other technologies. Their longer lifetime (over 20 years) is reflected in their substantially higher prices.
* Sheet metals tanks – very popular on the continent, they are much cheaper than stainless steel, and offer the best heat retention among the three types of tanks. They normally come with inner enamel glazing which reduces the build up of scale inside the tank. They are also the heaviest.
There are several important parameters to remember when choosing your unvented hot water cylinder:
* Volume and external dimensions – a typical household (4-5 people) in the UK will require a 200 liter cylinder. However, the cylinders come in different shapes and dimensions. Make sure to check the width and height of the cylinder, so that it fits in the airing cupboard (or any other space you plan to position the tank in).
* Heat retention – since the hot water cylinder is primarily there to store the hot water, it is important to check what insulation it has. The thicker the insulation the better heat retention it will have and less heat would be lost during the day. For reference, good cylinders lose less than 3 kW per 24 hours.
* Manufacturers service and warranty – although unvented tanks have good record of reliability (they have virtually no moving parts), it is important to note what warranty and service level is provided by the manufacturer.
Author: Tal PotishmanThis author has published 4 articles so far.