Water distribution systemsin buildings are required to deliver energy from where it is produced to where that energy is required within that building. The pipes, valves and terminal units are sized and selected from known design guide lines produced by professional bodies and manufacturers. Energy certification schemes encourage the use of controls, system diversity, innovative products, Commissioning and other ideas such as maintaining high delta T’s across Terminal devices. However, there is Energy certificate that is applied to the effectiveness of the design that could include pipe layout, the actual level of diversity applied and actual Delta T achieved.
Pipe layout and pipe sizing is key to ensuring maximum Delta T, but the fixed method of using flow to the terminal unit and return pipework to return the water back to the energy supply is universally accepted as the most energy efficient method of distributing energy within a building. Return pipe work is the necessary part to make two pipe system function. This waste in energy in a two pipe system is accepted and included in the energy assessment. Its use, won’t lose any points and yet it is an inefficient method of energy delivery. That to make the system work. Requires the addition of by-passes that destroy the return Delta T and the addition of valves that also destroy locally the differential Pressure generated by the pump. Not to mention the waste in installed return pipework that serves no other purpose but to bring back water that still retains usefully energy back to affect the performance of energy source.
Over the years there has been a number of different pipe layouts. Some have been designed for particular purposes such as A ‘Ring Main’ designed to ensure that water could always be supplied to a cooling unit in a Data centre. Other pipe layouts have been adopted to supply and control multi Terminals from a local placed flow and return Manifold. Other designs have been an attempt to reduce the amount of installed pipe work or alternatively the number of Balancing valves such as Reverse Return.
One Pipe System (Gravity Fed)
Relies on the Hot water Rising
Creates thermal Currents
Three days to warm a Building
First Radiator Small
Last Radiator Large
One Pipe system with Pump
Water forced around
Reduce size boiler
Quicker warm up
Very little Control
Two Pipe System Constant Volume
Three Port Control valve
Manual Balanced system
Inefficient Pump running maximum duty
Flow water mixed with Return
Loss of Delta T
Constant speed pump
Two Pipe system with By-pass
Pressure Increases Water is By-passed
By-pass valve to protect pump
Pipe lengths to all the units the same Length.
Ideal for equal Flow rates
Reduced number of Balancing valves
Increased pump head, more pipework
Central Distribution to many units
Ridged pipe up to the Manifold
Plastic or Multi Layered from the Manifold to the Terminal unit
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