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Hotter summers – the air conditioning turn off

As we approach what is predicted to be another scorching summer commercial property owners, facility managers and office managers will be under extreme pressure to ensure that their air conditioning plants can cope with higher, prolonged temperatures to maintain a cool comfortable working environment. Carl Webb identifies a solution for hire.

A recent survey to identify the effect of temperature on staff found that less than a quarter of office workers find the temperature in their offices comfortable, with more than a third suggesting they take at least 10 minutes out of work each day due to temperature alone. Results of the survey showed that an office of 100 people will have at least eight hours wasted each day, due to the temperature alone.

The air con system

Air conditioning systems are available in various designs to meet the specific and differing requirements of any building design, be it hotel, hospital, offices or industrial premises. They all operate with the same basic operating principle of using an air-to liquid heat exchanger.

Direct-expansion equipment uses refrigerant as the liquid medium whilst chilled-water can also be used as a liquid medium, in the case of the latter glycols can be added to prevent freezing.

Many factors influence the cooling capacity of air conditioning systems, the big influencing factor being the outdoor temperature. As it rises the air-flow increases, at higher air flow rates the latent capacity of the cooling coil is reduced. Indoor temperature and humidity also affect the total capacity of the AC system. As indoor temperatures increase, the sensible capacity can also increase.

Hot summers- the air-con turn off

With summer 2014 temperature forecasts in excess of 75°C over sustained periods, in-plant air conditioning systems will be under immense pressure, working longer hours and more aggressively to deliver a comfortable working environment. Plant failure must be avoided at all costs.

As we see the UK economy grow, particularly in the service sector, the good news is that previously empty office blocks will start to become occupied. The inplant air-conditioning units will be switched on, probably for the first time after many dormant months, even years. This scenario also applies to those bustling office blocks, as seasons change the boiler is closed down and the aircon turned on. Have premises and facilities managers been thoughtful enough to run the air-con in test mode prior to the summer season, identifying possible problems such as split pipes, seal failure, clogged vents or just an inability to power-up. Such a precautionary measure will ensure the system is ready for use. However with such unprecedented temperature levels, older systems just may not be able to cope. Organisations have to weigh-up the pros and cons of considering a full up-grade just for the summer season. Is it a viable investment? What are the alternatives?

The obvious choice is chiller hire. It is the ideal short-term solution and from the right people can be installed quickly and without disrupting the office workers. Many of these hired chillers add to the cooling efficiency of the installed plant during testing times.

Sustained summer temperature hikes also put modern systems under greater pressure resulting in the need for increased servicing. Here again the commercial reality of a call to a reputable chiller hire company is a must, their chillers enable the installed plant to be taken off-line to facilitate prompt service and repair.

As a temporary replacement or supplement to in-plant systems those responsible for plant efficiency and maintenance should have pre-established links with a competent hire company.

Hiring a chiller – check the facts

Many leading hire organisations will claim to provide 24/7, 365 day access to specialist engineering staff, there are just a few that can actually deliver on this promise and have a large nationwide network of depots that can respond promptly. In an emergency situation the customer faces the possibility of overheated sweltering offices, staff taking increased breaks to cool down and top-up fluid levels. Equipment failure is also a strong possibility.

Engineers from competent hire companies need to carry out a site survey to identify the best position to site a skid-mounted chiller, understand the chilling requirements and specify a chiller capacity that must also take into account ‘heat’ and ‘cooling’ losses from lengthy pipe runs, the greater the distance to the site inlet manifolds the larger the unit and higher costs.

Air-cooled, fluid chillers are available from most hire companies. They are easy to service which means customers are guaranteed fully tested and maintained chillers which can be installed more quickly than water cooled machines, quickly bringing a cooling normality to the working environment.

During operation air pulled from offices and passing over cooling coil heats the cooling water, the heated water enters a chiller barrel (also known as the chiller evaporator) which receives the systems cool low pressure mixture of liquid and vapour refrigerant, this then absorbs the heat from the water. This transfer of heat boils the liquid refrigerant in the chillers evaporator and the super-heated vapour is pulled into a chillers compressor. This compresses the refrigerant to a high temperature and pressure, high enough to allow the chillers condenser (a heat exchanger) to reject heat from the chillers refrigerant to the atmosphere by use of condenser fans.

Since the efficiency of an air cooled chiller relies on expelling heat into the atmosphere correct positioning of the hired unit is paramount.

Choosing the right hire company can certainly pay dividends – quicker response to cooling problems, competent engineers, faster delivery – and above all temporary installation of the right chiller to enable the office temperature to return to near normality.

// The author is a director of Andrews Chiller Hire //

3 July 2014

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