Once you’ve decided to refurbish rather than replace an air handling unit, the next question is usually what actually happens. Refurbishment covers a wide range of work, from a straightforward fan and coil upgrade through to stripping a unit back to its frame, so it helps to know how a project is put together.
Here’s how we run one.
1. Survey
Everything starts on site with the unit open. We’re looking at:
- Casing, frame and panel condition, and whether the structure is sound enough to build on
- Coil condition and performance
- Fan type, age and efficiency
- Filter housings and seals
- Dampers, actuators, and the state of the controls
- Access, including how we’d get components in and out of the plant room
We’ll also want to know what the unit is supposed to be doing, because units are often running loads they were never designed for after a building has been altered.
2. Scope and proposal
The survey turns into a scope. This is where the decisions get made about what’s worth doing. Replacing a fan assembly with EC fans may pay for itself; replacing a coil that has years left in it may not. Our guide to AHU lifecycle costs covers how we weigh this up.
If the casing is beyond economic repair, we’ll say so. AHU refurbishment vs replacement explains the tipping points.
3. Planning the works
Refurbishment almost always happens in an occupied building, so the plan matters as much as the work. We agree:
- When the unit can be taken offline, and for how long
- Whether temporary ventilation is needed
- Access routes, lifting, and out of hours working
- Permits, isolations and coordination with the site team
On the fan assembly upgrades at Colmore Row in Birmingham, the building carried on working around us throughout.
4. Works on site
Typical refurbishment work includes:
- Fan replacement, usually moving to EC plug fans. Our guide to EC vs AC fan motors explains the difference
- Coil replacement or recovery, covered in our AHU coil replacement guide
- Casing and panel repairs, insulation replacement and sealing
- Filter housing upgrades to improve sealing and grade
- Damper and actuator replacement
- Heat recovery, either refurbishing what’s there or adding it, as covered in retrofit heat recovery systems
- Controls upgrades, so the unit can be run properly once it’s back in service
5. Commissioning
A refurbished unit needs commissioning like a new one. Airflows are set and measured, controls are proved, and performance is checked against the design. Our article on AHU commissioning explains why this stage is worth the time it takes.
Skipping commissioning is the most common way a good refurbishment ends up underperforming.
6. Handover and ongoing care
You should finish with updated documentation, commissioning records and a maintenance schedule that reflects the new components. Filter grades, belt sizes and spares lists all change after a refurbishment, and if the records don’t change with them, the next engineer is working blind.
From there, planned maintenance protects the investment. See AHU maintenance contracts: what’s included.
How long does it take?
It depends entirely on scope. A fan upgrade may be a matter of days. A full strip and rebuild with coils, casing work and controls will run to weeks, and lead times on components are often the longest part. Our guide to AHU spare parts sourcing and lead times is worth reading before you plan around a date.
How we could help
Refurbishment is one of the main things we do, and it’s often the quickest route to better performance without the cost and disruption of replacement. See our AHU refurbishment services page for what we cover.
Get in touch for a survey.
Frequently asked questions
Usually, particularly where the casing is sound and access is difficult. Where corrosion has taken hold or the unit is badly undersized, replacement is often the better investment.
Rarely. Most refurbishments are planned around the building’s operation, with works timed to suit and temporary ventilation where it’s needed.
It depends on what’s being replaced. Moving from old AC fans to EC fans and getting the controls working properly often makes a significant difference to fan energy.
