Dualstream Choosing the Right System

Dualstream and Coldstream are registered trade names of GAH.

Choosing the right system for your property is important and there are many factors to take into consideration. The most important is carrying out adequate pressure and flow readings to establish the strength of the main supply, and that it would support such systems.

  • Flow rate: is the amount of water carried in the pipe work, measured in gallons or litres
  • Pressure: is the force of water delivered, measured in bar or PSI
    (pounds per sq inch)

These simple tests can normally be carried out by your nominated heating engineer or competent person, and can be obtained from your local water authority. Read more

Taking into consideration the pressure and flow readings, the number of bathroom, ensuites hot/cold outlets, number of people in the property, and the shower/bath specification and flow rates are all equally important. Looking at the different options to heat the cylinder is more important than ever before, with gas and oil prices rising and the use of electric and renewable energies are becoming more popular. All these factors must be discussed before ordering the model of your choice. Your heating engineer or installation company will be happy to discuss this with you and we are only a phone call away to discuss our products their application and your requirements. There are generally three popular ways of heating unvented cylinders.

Indirectly heated

Indirectly heated cylinders are designed to be run in conjunction with a primary heat source, normally a gas, oil central heating boiler. The cylinders are supplied with a primary coil to connect to the boiler along with an immersion back up. This is the most commonly used type of mains pressure hot water cylinder.

Directly heated

These cylinders can be heated units fueled by gas or oil, but generally the term is given to cylinders heated by electric immersion. Our direct cylinders are supplied with two 3kW immersions and can take full advantage of the many economy tariffs now available. Given that they need only mains water and an adequate electrical supply these stand alone units are very versatile and can be installed almost anywhere in the property.

Renewable energy - Twin coil solar systems

There are many different types of renewable energies now available to customers making our fuel choice varied and in some respects more difficult. What we can say is that fossil fuels are slowly diminishing and when considering a new heating and hot water system taking into account the use of renewable energy must be given serious consideration and the benefits to our planet and ourselves both financially and morally. Read more

Over the last few years the renewable market sector has seen unparalleled growth in products like wind turbines, ground heat source pumps air- heat source pumps, and zero rated carbon emission products like pellet boilers. One of the most popular renewable products to consider is Solar. Enhancing solar energy is free and offers good savings on heating hot water and in time offers quicker payback periods than other energies taking into account installation costs.

Standard Solar systems incorporate a form of collector, the solar panels and a sealed control kit with safety valves. The collectors absorb the suns energy and channel the energy through the system to the coil in the cylinder providing an energy source to heat the hot water, and during long spells of sunlight or good daylight savings of up to 60% can be made on your hot water costs.

GAH offer Dualstream systems with two twin-coiled cylinders, which can be used in conjunction with Solar panels or other energy sources. The design of the cylinders differs slightly from the standard range, with the inclusion of a second heating coil, twin immersions and thermostats. These cylinders are extremely versatile and offer customers many options in the way the cylinder can be heated. Technical details can be found in our technical specification and manual.

Installation Criteria

Most if not all unvented cylinders require adequate pressure and flow rates with the minimum level around 1.5 bars and 20-litres/m-flow rate. It is always recommended that a 22/25mm main supply pipe should be used. But many houses have 15mm supplies or flow rates lower than 20 litres, and if installed and unvented cylinder will suffer from pressure and flow fluctuations if more than one outlet is used at the same time. Read more

Dualstream systems still require adequate pressure of 1.5 bar and above but given the right size accumulator and space we can install our systems on flow rates as low as 9 litres a minute, and on 15mm supplies.

Consult your heating engineer on your application and model size requirements and always remember that choosing the right position for both the accumulator and the unvented cylinder is important taking into account access and future service requirements.

The sizing chart has been compiled to give an indication of the type
of system installed for most house types. It is only a guide and we strongly recommend all the above factors be given careful consideration.

More than one accumulator can be linked together to create the required cold-water demand and hot water cylinders can be linked in series to provide greater volume. GAH offer free sales and technical advice along with a design service, to architects, heating engineers, developers and end users.