A realistic balance

One of the challenges facing many specifiers and their end clients is the need to ensure comfortable conditions for the internal environment while keeping any damage to the external environment to a minimum. In this respect, air conditioning often finds itself cast as the villain of the peace.
While natural ventilation may be the ideal that many designers aspire to, in reality the vast majority of commercial projects will need some mechanical cooling. This may be because of high internal heat gains, high solar heat gains in a highly glazed building or simply that the layout of the building does not lend itself to effective natural ventilation.
Whatever the reason, there will be many occasions where it’s necessary to specify an air conditioning system – so having accepted the inevitable the key is to opt for maximum efficiency. In this respect, I would suggest that more can be done by everyone in the supply chain, from the end client to the supplier of the equipment.
In many cases, of course, the end client may not have the technical knowledge to know what’s required; that’s what specialist engineers are for. They may, however, have a general idea of what they want. Some may be motivated mainly by the capital cost of the project, while others will be more inclined to take a longer term view and consider the whole life costs. And there are always those that want to have their cake and eat it with the cheapest and most efficient option.
Given that the latter option is pretty unrealistic, a compromise is inevitable and the specifier can do a great deal to educate the end client and explain the reality by providing comparisons relating to whole life costs. On the assumption that the client agrees to pay more up-front to save money and reduce carbon footprint in the longer term, there is also an onus on the specifier to stick with the specification that’s been agreed.
This means that the procurement process also needs to be realistic. If the contractor is going to be selected on the basis of lowest price this will be an open invitation to break the specification. Equally, it would be good to see contractors being more receptive to the idea of cost of ownership and offering the best long-term value to the client.
In parallel, there is a great deal that those of us who are involved in supplying the products can do. Manufacturers can ensure that they continue to improve the efficiencies of their products and discontinue those products that no longer offer acceptable efficiencies. Similarly, we have to recognise that someone who is specifying all of the mechanical systems for a project can’t be expected to be an expert on every item of plant available from every manufacturer. Here, manufacturers and distributors can help by making relevant, accurate and trustworthy information easily available. We can also make sure that we use consistent forms of performance measurement so anyone comparing products doesn’t have to go through the rigmarole of converting different figures.
Beyond the way we present information there is a great deal that knowledgeable suppliers with in-house technical expertise can do to help the design process. Experience shows that choosing the main items of plant is only part of the story, it’s also important to understand how those items interact with the rest of the system and how that interaction will affect overall performance and costs.
So, for example, you may tick all the right boxes in selecting a chiller and ensure that it has a high COP at part-loads, continuous capacity control and uses DC motors. But what about the control of the chiller(s) – particularly in a multiple chiller installation? Can they be configured to avoid peak currents and the need for oversized cables? Does the chiller have a high power factor so it’s unnecessary to install a series of capacitors to compensate for the reactive energy consumed by the motors?
These are just a few examples of factors that are sometimes overlooked but which can make a significant difference to the overall cost of ownership. There are some in the industry who would take a ‘caveat emptor’ approach and not feel it was their role to highlight these considerations to a specifier.
Personally, I feel that all of us involved in the industry, whatever our role, have a duty to work together for the good of the industry’s clients because in the long term this is for our own good.

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