Unvented hot water systems

If you’re building a new property or looking to upgrade your old one then look into installing an energy efficient unvented hot water and heating system.

If you live in an older property with ancient, unreliable central heating and have fluctuating hot water and poor pressure showers, then it’s a good idea to install a new unvented central heating system. Similarly, if you’re building a new property then an unvented heating system is your best bet.

What is an unvented hot water system?

There are two types of central heating system; an open vented and an unvented system:

Open vented central heating systems

These were commonplace in the UK before unvented systems were made legal in 1986. A hot and cold water tank is usually installed in the loft, as they need to be at least one metre above the radiators for the heating to work. Cold water is stored in one cylinder and fed to the hot water tank; which has an open vent pipe to release steam into the atmosphere. An open vent central heating system does have some drawbacks; it can be noisy and because of its location in the loft, pipes and tanks are liable to freezing. There is also a risk of water contamination as well as unreliable water pressures and temperature fluctuations.

Unvented central heating systems

Since introduced to the UK, these systems have grown in popularity. An unvented system doesn’t have a cold water tank and the sealed (unvented) hot water cylinder is instead fed directly from the cold water mains. Unvented systems can be dangerous so a number of safety features have been incorporated into their design, including: cylinder thermostats, expansion release valves, back flow pipes and air gaps to allow for expansion. Unvented cylinders come in a range of sizes and can be made of copper, stainless steel or low-carbon steel. There are two types of unvented system:

Indirectly heated unvented systems – are connected to a traditional heat source such as a boiler or perhaps solar panels. This is the most common type of unvented system and is fairly easy to install when converting old central heating systems.

Directly heated unvented systems – these are fuelled by electric, gas or oil directly and are used often in brand new properties. Before you consider installing an unvented system you must make sure that you have a mains water supply which is capable of producing a minimum flow rate of 1.5 bar and 20 litres per minute flow rate.

Advantages of an unvented central heating system

  • Good water pressure for more powerful showers – so you won’t need a separate shower pump anymore.
  • Quicker and more energy efficient at heating water; this will save you time as well as money on running costs.
  • Can be fitted to better performing taps and faucets.
  • Easy to install and can be placed anywhere, for example in the garage.
  • Space saving because you don’t need a cold water tank in the loft, which is particularly good if you want to convert your loft.
  • Are reliable and low maintenance.
  • More hygienic – in comparison to water stored in a tank, which is at risk of contamination.
  • Less risk of frozen pipes.

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