Sustaining HVAC Performance

Sustaining HVAC Performance

Refurbishing items of HVAC plant, rather than buying new equipment, can not only save on capital and running costs, it also contributes to sustainability policies by reducing the use of raw materials.

Looking at some of the key considerations:

Many operators of processing, manufacturing and logistics operations are faced with improving their sustainability performance while also reducing overheads. To some extent these imperatives are driven by initiatives such as the Carbon Reduction Commitment Energy Efficiency Scheme, and there are often parallel aspirations that come from the company’s Corporate Social Responsibility strategy.

In this respect, it’s important to consider the wider sustainability picture, which goes beyond the high profile issues of energy consumption to encompass environmental impact through the life cycle of equipment and buildings. These include issues such as embodied carbon and maintenance requirements.

However, it’s certainly true that, in many cases, one of the first areas that comes under scrutiny is energy efficiency - and the HVAC plant in many such facilities certainly makes a contribution to overall energy consumption. Consequently, investing in measures that will improve HVAC efficiency are certainly worth considering, but that doesn’t necessarily mean making a major capital investment in new plant.

There are many situations where refurbishment of air handling units, space heaters, fan coils, chillers, boilers and all manner of other plant items can significantly improve performance and efficiency at a fraction of the cost of buying new.

Furthermore, not only does refurbishment consume fewer materials and their associated embedded carbon, it also reduces ongoing life cycle costs - and the cost savings can be substantial. For instance, in the case of air handling units (AHUs), depending on the extent of works required, we have found that refurbishment can cost between 20% and 50% less than the replacement option.

Looking at a specific example of an AHU refurbishment, we can compare the costs related to a 2m x 2m x 6m AHU with an airflow of 7m³/s. It incorporates a volume control damper, bare tube frost coil (LPHW), panel filters to F4 efficiency, bag filters to G6, CHW cooling coil, LPHW reheat coil, fan and motors. Supply and installation of such a unit, based on good access, would cost in the order of £12,500. To refurbish a similar unit, replacing all internal components, treating any corrosion, replacing damaged external panels, re-commissioning and providing a 12 month warranty would cost £9,125 – a saving of 27%.

As mentioned earlier, the overall life cycles costs – including energy consumption and maintenance - are also an important consideration and in this respect there are additional benefits. For instance, the newer components within a recommissioned system will reduce maintenance costs while also increasing energy efficiency, so the cost of ownership is lowered and the payback is faster. The Operation & Maintenance manuals will also be updated or, as with many older buildings, supplied for the first time in the life of the plant.

In the case of AHUs, fan coils and other items of equipment, general wear and tear through the life of the plant will lead to deterioration of components and casework. Very often, though, the equipment continues to perform rather than breaking down completely, so the gradual fall-off in performance can go unnoticed for many years. This is where expert input can be of great value.

In such cases, the inherent flexibility of the refurbishment approach is a real advantage because it focuses just on the aspects of performance that need to improve, making it a more elegant and precise solution. For example, age deterioration will affect some components more than others and moving parts in fans and motors will clearly experience more wear and tear than static components. In AHUs, cooling coils may also have suffered from the effects of corrosive oxidation, caused by condensate mixing with airborne pollutants. So there may also be geographic variation in line with air pollution levels.

As a result, the extent of the refurbishment can be tailored very precisely to the condition of individual items, so an initial inspection of the plant to identify opportunities for refurbishment is the first stage in any such project. Here, it often makes sense to bring in specialists in this field to carry out the inspection, produce a method statement, risk assessment and detailed costings.

This is also an ideal opportunity to identify ways of improving both energy and comfort performance, as it’s almost certain that the building’s usage will have changed since the plant was specified. We often encounter situations where heat gains have increased through higher occupancy densities and/or increased use of electrical equipment, so the plant may already have been struggling to cope with the higher cooling demands. Improvements to building fabric may also change the dynamic of the internal environment.

Using newer designs of components that comply with modern standards and specifications can help to boost performance – and do so more efficiently. For example, the original fans and AC motors in an AHU may be replaced with backward-curved fans and DC motors to achieve higher efficiencies through reduced fan power consumption, while newer direct expansion refrigeration equipment will offer higher efficiency than older designs. Similarly, heating and cooling coils now deliver more efficient heat transfer than used to be the case, filters are more efficient and AHU panels with much improved thermal and acoustic insulation can be supplied.

In some instances, replacing the components may not be sufficient to achieve the required performance but an AHU refurbishment can also include the replacement of whole sections, or addition of new sections to supplement what’s already there.

The refurbishment approach can also avoid the access problems that are frequently encountered in existing, occupied buildings and often make plant replacement a major challenge. Even when new sections are required these can be assembled on site, so that access is not an issue.

Working in occupied buildings also necessitates minimising disruption to the occupants and flow of work and a well-planned AHU refurbishment can easily overcome this problem as the work can be carried out in phases outside normal working hours. And where the AHUs are serving critical areas these can be isolated so that business-critical services are unaffected and downtime is avoided or minimised.

This isn’t to say that refurbishment is always the best option but it is certainly one that ought to be considered more often, and probably will be as sustainability becomes a more important element of the project planning process. Given the potential financial and environmental benefits it also makes sense to team up with companies that have experience of plant and equipment refurbishment and can provide a comprehensive service from feasibility studies and design through to commissioning.

For enquiries or more information contact Envirotec Ltd