Traversing the maze of boosting performance
The demand for pressure boosting has grown consistently in recent years as a result of taller buildings, more condensed living, inconsistent site pressure and reduced mains pressure. These factors combined with the need to reduce the plant room size into the smallest possible footprint, has made the selection process much more complex, says Glynn Williams
There is an increasingly wide range of booster solutions available to building services specifiers - but how do you decide which system is best for your particular application?
Where to start
To make sure you are taking the correct factors into consideration when sizing a booster set a number of areas should be included within the calculation.
The actual system configuration needs to be established taking into account the volume and position of water storage - basement, intermediate, roof-top. The next step is to define the actual flow. There are quite a few tools available to assist with this calculation in a single-use building.
However, this is a much more complex calculation in a mixed-use building and this is an area where we suggest seeking guidance from an experienced booster manufacturer, in order to ensure the set will meet all the requirements for that particular solution as well as being as energy efficient as possible.
One common error that is made at this stage is to size the set based on all the appliances running together at maximum demand - this is very rarely the case and will result in over-sizing.
Over-sizing any booster set will result in a larger and therefore more expensive set being purchased than the system actually needs as well as it costing considerably more in energy terms over the course of its working life.
The next step is to define the consumption and load profiles, which is another challenging aspect that needs to be undertaken to establish the appropriate 'stages' in getting the best booster selection and will help to define how many pumps (or sets) are ideal for the particular application.
The final step in the selection process involves determining the pump's duty; this is calculated based on the static height, friction losses and required end-pressure.
Prior to final specification it is important to consider the equipment footprint, especially where it is a key aspect. For example variable speed option boosters offer the combined space and energy savings that are so often a prerequisite of building service projects today.
Maintaining a healthy flow
All of these factors are general pointers. However certain projects need to be viewed differently, depending on the application.
One of these instances is when considering meeting the water pressure demands in a hospital - from both a new-build as well as a refurbishment perspective.
The number of patients that the NHS deals with is staggering - on average one million patients every 36 hours, which is equivalent to 463 people a minute.
Hospitals are a very significant part of today's NHS, and also play a key role all our lives as they are the main providers of acute and maternity care as well as still playing a significant role in providing geriatric support.
Because of their role they are the original 24/7 outlets as they always remain open for business.
This means that the demand from plant equipment also needs to operate 24/7 - week in, week out.
Add to this the need to maintain a high ambient temperature and specific requirements for services such as constant hot water, and this all leads to an extremely high demand for energy.
This fact was graphically highlighted by a report that was issued after a government survey that measured the annual emission of greenhouse gases by the public estate in England and Wales.
With hospitals using an average of 4,089 tonnes of CO2 emissions each year, they took the top place as the worst energy offenders.
Royal London case story
However, this situation is changing and a good example of this is one of the higher profile new hospital developments in the UK in recent years - The Royal London.
With a history that can be traced back to 1740, The Royal London has entered yet another new era. It recently underwent an extensive redevelopment that cost £650m and which has transformed it into a state-of-the-art medical centre delivering world-class facilities.
Occupying an area equivalent to 40 football pitches, the now 6,000 bed hospital is comprised of a cluster of inter-connected glass buildings that include two 17-storey towers - one of which is equipped with a helipad - and a 10-storey tower. The tallest building on site is 284ft, which is the same height as Elizabeth Tower, which houses Big Ben.
This hospital is a totally sealed building which means that the windows do not open - it is fully ventilated with 100% fresh air that is treated before it comes into the building. This means that noise is reduced and this also helps to control infection.
The pump solution needed to be no less impressive and had to deliver energy efficient pumps for all the heating, chilling, hot water service systems and chilled water as well as the pressurisation units and packaged booster sets, that are such a vital part of the hospitals infrastructure.
In this particular instance a total of seven separate booster sets of various configurations form the solution to this particular aspect of the project.
Hospitals are at the heart of any community and The Royal Hospital is already delivering excellence in health and welfare to the local and wider area.
Since it opened it has continued to meet its objectives and is successfully meeting both the clinical as well as the strict energy targets it set itself - a point that is borne out by statistics that show 134,636 A&E attendances; 80,020 hospital admissions; 4,600 births and 129 helipad emergency landings - all in just one year.
Getting the booster requirement right on projects such as this, cannot be left to chance, you need to ensure that you are speaking to a manufacturer that has not only the knowledge to deliver, coupled with the product range and engineering expertise to deliver the best applicable solution.
Additionally, today there are more frequent instances where external approvals such as WRAS certification are sought, either relating to the components or indeed the actual sets themselves.
It is therefore important to ensure that you speak to people who can deliver, regardless of the demands of the specification.
Modern living has dictated that booster systems are here to stay and they will need to deliver a reliable, efficient and adaptable solution to meet the demands placed upon them both for today's needs and tomorrow's expectations.
// The author is director of sales - commercial building services at Grundfos //
13 August 2013