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To Refurbish Your Air-Handling Units Or Not To Refurbish? – These Are The Questions

Many people are unfamiliar with the workings of air-handling equipment. Certainly from what we have witnessed over the years, if you’re lucky, you may get filters and drive belts changed and that’s about it.

But air-handling units are expensive items of capital plant, often costing many thousands of pounds. What they are not, are fire and forget items and they need regular inspection and maintenance by people with the knowledge of how they work and the consequences if a part is left to deteriorate.

With ‘proper’ maintenance by a knowledgeable company, an air-handling unit will last indefinitely. Possibly beyond the useful life of the building it serves.

But this rarely happens and so often units are just left to quietly fall into disrepair, until someone decides that they now need to be expensively replaced, with all the cost and disruption that may incur.

But that need not be the case, as so often refurbishment in situ is the most economic solution to the problem of ageing air-handling and ventilation equipment.

Before deciding to replace equipment, ask yourself some of the following questions.

What is the condition of the casework?

Corrosion of the casework needs to be carefully assessed. Whilst more likely on weatherproof units, internally located equipment may have had leaks from heating or cooling coils, or from incorrectly trapped cooling coils.

Causing water to remain and corrode the case.

However, depending on the level of corrosion, it often can be treated or plated and this can be advised upon.

How long will the unit be required for?

We would consider that refurbishment will extend a unit life by at least 10 years and with good maintenance, indefinitely.

Is there space for a new unit with heat recovery that complies with Part L2 (2018) of the building regulations?

New units now require high-efficiency heat recovery devices, such as thermal-wheels, crossflow plate heat exchangers or runaround coils - This means that they can be up to 25% larger than original units!

Are the supply and extract ducts located at the unit position?

If the supply and extract airflows do not come together. Then the only option for heat recovery will be to fit runaround coils and then pipework needs to be run between supply and extract AHU’s.

What access is there to the unit location? Can the old unit actually be removed? Will the new unit fit? Refurbishment should especially be considered if existing equipment is located within a tight plantrooms or has restricted access routes, or possibly those on the roofs of tall buildings where any craneage would be difficult and expensive.

Do you need a higher degree of filtration or different means of heating/cooling than is provided by the existing AHU?

Poorly fitted or incorrect filters are common on old equipment leading to contaminated air bypassing and clogging up heating and cooling coils, plus atmospheric staining around grilles. However, filter frames can be replaced during refurbishment with new to prevent bypass.

Filters may also be upgraded during the refurbishment of an existing AHU. Other items may also be replaced, for instance an electric heater with gas or DX heat pump coil

What condition are the controls in?

Control technology moves on at a pace and the original unit controls may be outdated. However there are many economical ways that old controls can be interfaced with a new BMS during a refurbishment.

What condition are the heating and cooling coils in and also the valves controlling them?

Bent fins can be combed. But if the fins are rotting, then the coils need to be replaced and so disconnected and drained. Space for coil removal needs to be considered. But old coils can be cut up and removed and new coils replaced in sections and even flat-packed.

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Are there any noise level issues you need to consider?

Any noise breakout from either the equipment or ductbourne noise can be investigated and measured and then retrofit acoustic solutions be designed and installed if required.

Are existing DX coils running on old gases?

Old coils running on gasses such as R22 can easily be replaced, along with their associated condensers during a refurbishment.

The above is not an exclusive list, but the most common considerations to ask when assessing existing AHU for refurbishment. Acted on correctly refurbishment will extend the of existing plant by at least another 10 years.

Compliance with Part L2

New units must comply with Part L2 of the building regulations. This means they will become much larger and more expensive. Refurbishment may circumvent the need for this.

The opportunity to reduce consumed energy

Refurbishment can also be a great opportunity to reduce the amount of energy consumed by retrofitting items such as; new fan technology, better controls and control over existing plant, lower energy forms of heating or cooling.

A chance to review a potentially out-of-date system or technology

It gives designers the opportunity to review the system. For instance: The air volume could be changed if the building usage has changed. Or could this be an opportunity to reduce the risk of transmission during refurbishment by adding UVc or other virus reducing technology? All these questions and more can be considered at this point.

It is so often the greenest solution

It’s certainly the greenest solution. Very much embracing the ‘re-use’ mantra from Reduce, Re-use or Re-cycle. Without even considering the embedded energy in manufacturing, transporting and installing new equipment.