AHU – Replace or Refurbish?

Good Question.  Here in New England, we have lots of buildings with old and deteriorating air handling units.  In many cases, the clear choice may be to replace the old AHU’s; however, there are many reasons, not just financial, as to why repair or refurbishment alternatives should also be explored.

Why Buy New?

This is America, we like new stuff.  With a new AHU, you get a brand new product with all the latest bells and whistles, including most energy efficient designs.  New units are available for a wide range of applications.  New units can also come with the latest casing materials, like composite and aluminum, which can provide lifetime warranties.

New AHU Pros

• Suitable for a wide range of applications
• Can increase unit capacity
• High efficiency heat recovery options available
• Lifetime casing options available
• Low energy / high efficiency fans
• Custom designed units to fit existing spaces

New AHU Cons

To retrofit a new AHU to an existing system is an option; however, the ability to do that may be extremely difficult.  Existing space and duct runs may make change out nearly impossible.  There will also be associated costs with modifying all services and steel work to suit the new unit, and possibly a crane to remove the old unit and site the new one.

Why Refurbish an Existing Unit?

Refurbishing of existing air handling equipment can be a practical alternative to replacing with new.  Keeping the old equipment has several advantages.

AHU Refurbishment Pros

• Cost Effective – As an example, the refurbishment cost of existing equipment can be around 35-50% of the cost of new equipment (excluding removal and re-installation costs). New components can often be designed to further save crane and rigging costs.  If budgets are tight, replacement can be limited to essential items only.
• Less Disruption – Work can be scheduled so as not to disrupt the owner’s operation.  Work can also be conducted overnight or on weekends.  Building occupants want as little disruption and downtime as possible when dealing with air handling units. Downtime is inconvenient and potentially disruptive and costs money, so a solution that will minimize any inconvenience and save money in both the short and long term is essential.
• Less Time – Refurbishment is often faster than replacement. The customer can choose to separate the necessary work and complete it at different times for greater flexibility. For example, a gas burner can be replaced one weekend, a cooling coil and other components on another.
• Upgrading Equipment – This could include adding a cooling coil, heat recovery, higher grade filtration or upgrading with the latest energy saving fans. Increased efficiency means running costs can be improved by a considerable margin.

AHU Refurbishment Cons

• Increased Capacity – Realistically, the only limitation with a refurbishment will come down to the limitations of the old AHU; it cannot be configured to deliver more capacity than what it was originally designed for.
• Qualified Contractors – AHU refurbishment is a way of life in the UK and Europe.  There are complete companies that specialize in this type of work.  Here in the US, this is not an option.  Typically we need to refer mechanical contractors that will do this work as a portion of their business.

What can be Refurbished on the AHU?

With equipment in poor condition, there can be substantial improvements. Once the refurbishment has been completed, and assuming that it’s been properly maintained, a good refurbishment can add around 15-20 years working life to existing equipment.

• Heating and Cooling Coils – For units with limited access, new replacement coils can be provided in sections which are then joined together on site, also replacing valves and actuators as required.
• Gas Heaters –  Gas heaters can be repaired or replaced, if you choose to go with a gas heater repair, just make sure to find a professional who can do the job right.
• Dampers – Jammed dampers are one of the most common causes of AHU’s not working properly and are easily repaired or replaced.
• Filters and/or Filter Racks – Often older units have air filters that fit poorly thereby allowing the bypass of unfiltered air.  Filter frames can be replaced and fit with higher grade energy-efficient filters as required.
• Fans –  All centrifugal or axial fan types can be repaired or replaced by most air conditioning services.  We recommend that fans should be replaced with the latest energy efficient direct drive ECM fans (Q-PAC).  Replacing old forward curved fans with new plug fans can use 15-20% less energy.

CONCLUSION

The physical condition and changes to building use (i.e. number of occupants) will determine what can or cannot be done with the existing equipment and of course, financial implications will have to be taken into account too.

Refurbishment can often be quicker solution and programmed to be completed sympathetically with little down time and effects on the buildings ventilation system.

Be it a new AHU or existing, remember that regular service of the units will prolong the unit’s life and deliver the required capacities for the duration of its life.  For help determining whether you should replace or refurbish, contact us today.

Q-Pac
Aquis
Cox Engineering
Capital Coil