Are Unvented Direct Cylinders Any Good? Yes, direct unvented cylinders can be excellent but are best suited to the right type of property and demand for hot water. Direct unvented cylinder: A direct unvented cylinder uses electric immersion heaters fitted directly into the cylinder to heat the water and store domestic hot water under mains pressure. Unlike an indirect cylinder, it doesn’t need a gas boiler, oil boiler, heat pump or external heat source to heat the stored water.

Advantages of unvented direct cylinders

One of the advantages of a direct unvented cylinder is that it can provide excellent hot water pressure without the need for a cold water storage tank in the loft. A direct unvented cylinder can provide showers, baths, basins and sinks with excellent pressure, as long as the incoming mains water pressure and flow rate are suitable. This makes it a popular choice for flats, apartments, small homes, offices, commercial washrooms and properties where there is no gas available.

Direct unvented cylinders are also relatively straightforward in heating terms. They use one or more immersion heaters to heat the water, meaning there is no boiler circuit, heating coil, flue, gas pipe, oil tank or combustion process involved. These features can make them useful in buildings where it is difficult, expensive or unnecessary to install a traditional boiler system.

Please refer to the following webpages for more information

Our range of 80 to 500 Litre direct unvented cylinders in stainless steel

or our commercial range of direct water heaters, which goes up to 6,000 Litres in volume 

Commercial electric water heaters up to 6,000 Litres 

Flexibility of operation

Another advantage is flexibility. Many direct unvented cylinders have twin immersion heaters. This enables the cylinder to heat different sections of stored water. For example, one immersion heater may heat the whole cylinder; another may heat only the upper section for smaller hot water loads. They also work well with off-peak electricity tariffs where the cylinder is heated overnight and stores hot water for use during the day.

But direct unvented cylinders aren’t the best choice for every application. The main disadvantage is the running cost. Depending on energy tariff and usage pattern, they can be more expensive to run than a cylinder heated by a gas boiler. They use electricity to heat the water directly. They are best where hot water demand is moderate, gas is unavailable, or an all-electric system is preferred.

The electrical supply also has to be appropriate. Immersion heaters are generally high-load appliances, and therefore the installation needs to be correctly designed with the correct cable size, protective devices, controls and isolation. Larger systems or multiple immersion heaters may require careful assessment by a qualified electrician.

Unvented components 

As with all unvented cylinders, direct models require the correct safety controls. These systems usually include a pressure-reducing valve, an expansion vessel or internal expansion air gap, an expansion relief valve, a temperature and pressure relief valve, a thermostat, a thermal cutout, a tundish, and discharge pipework. A competent person who is familiar with unvented hot water systems should carry out the installation and servicing.

Conclusion

Overall, direct unvented cylinders are a good option for many properties, especially where mains pressure hot water is required and there is not a suitable boiler or gas supply. They perform impressively, are easy to operate and are simple to install, but you should always check out running costs and electrical requirements before choosing one.