Air handling & fan coil units
Air handling and fan coil units, set, connected and commissioned
A unit that has been dropped in a plant room is not an installation. What makes one is the plinth it stands on, the vibration it does not pass into the building, the connections that do not leak, and the access panels the person servicing it in five years can actually reach.
The unit is specified. The installation is what you get.
By the time an air handling unit reaches site, somebody has already chosen it: the duty, the coils, the filters, the controls. What is left is everything that decides whether it does that job for twenty years or becomes the plant room nobody wants to go into.
That is the work we do. Getting a heavy unit into a space that was not built around it, standing it on something that does not pass its vibration into the slab, connecting it with joints that stay sealed, and leaving the filter doors, the drain and the fan section somewhere a person with a toolbag can actually reach.
We install to a consultant’s design and coordinate it with the other trades on site, and on smaller commercial jobs we set the system out ourselves. Either way the unit is commissioned and the figures are written down.
Getting it in, and keeping it still
Plinths, mounts and flexible connections
A fan section is a rotating mass bolted to a building. Set it straight onto a slab or a steel frame and every hum it makes travels through the structure into the office or the classroom above — and no amount of work on the ductwork afterwards will take it back out.
- A level plinth or support frame, so the drain falls the way it should and the doors close square.
- Anti-vibration mounts matched to the unit, so the plant sits on them rather than through them.
- Flexible connections between the unit and the ductwork, so the duct is not a second path for the vibration.
- Attenuators either side of the fan where the run serves somewhere that needs to be quiet.
- A condensate drain with a trap, run to a fall and tested with water before anybody signs it off.
The part that decides the running cost
Access that is still there after the ceiling goes in
Filters have to be changed, coils cleaned, drains cleared, belts and bearings looked at. A unit where any of that means taking down a ceiling tile grid, moving a cable tray or standing on a pipe is a unit that stops being maintained, and a unit that stops being maintained quietly stops delivering its duty.
So access is set out with the unit rather than discovered at handover: clearance in front of every door, access panels in the duct at the dampers and the attenuators, and isolation where the next engineer needs it. It is the least glamorous thing on the job and the one the facilities manager thanks you for.
Fan coil units are the same argument at a smaller size and a larger number — a floor of them above a ceiling grid, each one needing its filter changed and its drain clear, in a space that is easy to lose once the grid is in.
How the job runs
Sized to the programme, and planned around the one day that matters most — the day the unit arrives.
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Survey and lift plan
How the unit gets from the lorry to its position: door widths, floor loading, whether it comes in whole or in sections, and what has to be in place before it arrives.
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Supports and first fix
Plinths or frames set level, primary ductwork and connections run to the unit position, and the zone agreed with the other trades.
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Set and connect
The unit placed on its mounts, flexible connections made, attenuators and dampers fitted, drain trapped and run to a fall.
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Commission
Flows measured and set against the design duty, dampers regulated, and the readings recorded for the O&M manual.
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Handover
Commissioning figures, filter schedule, access points identified, and the option of a planned maintenance visit so it keeps meeting them.
What we install
- Air handling units, whole or delivered in sections
- Fan coil units above ceilings and in bulkheads
- In-line and mixed-flow fans
- Plinths, support frames and anti-vibration mounts
- Flexible connections, attenuators and dampers
- Condensate traps and drainage to a fall
- Access panels and isolation for maintenance
- Commissioning figures for the O&M manual
On a roof
Plant outside has to be weathered and held down
A roof is the hardest place to put plant and the easiest place to cut a corner, because nobody goes up there. Ductwork on a roof has to be supported so it does not sit in standing water, weathered where it goes through the covering so the roof does not start leaking into the room it was meant to cool, and fixed down against the wind.
That is most of the work nobody sees, and it is the difference between an installation that is still dry in its fifth winter and one that is the reason for a roofer’s callout.
Where this sits next to the other services
Questions we get asked about air handling units
Either. On most commercial jobs the unit is scheduled by the consultant and bought through the main contractor, and we set, connect and commission it along with the ductwork. On smaller jobs we can specify and supply it ourselves. What we will always want before the delivery date is the unit’s dimensions, weight and section breaks, because getting it into position is decided long before it arrives.
Yes, and most of our commercial work is exactly that. The sequencing that matters is getting the primary ductwork and the supports in before the ceiling grid and the other services close the zone, and being ready on the day the unit is delivered. We coordinate on site with the other trades rather than working round them afterwards, because a duct zone on a drawing and the space left once the sprinklers and the structure are in are not always the same space.
No. Refrigerant circuit work — recovery, charging and leak testing — is carried out under F-Gas certification by our refrigerant partner, because it is illegal to do otherwise. We do the mechanical installation, the ductwork, the condensate and the air side of the commissioning, and we coordinate the two so the job is handed over as one.
Often, yes. Noise from an air handling unit is usually one of three things: vibration getting into the structure because the unit is on failed or missing mounts, a rigid connection to the ductwork carrying the vibration along the run, or air noise from a duct or damper that is too restrictive for the flow. The first two are relatively cheap to put right. The third needs measuring before anybody guesses at it. We would look at all three before anybody talks about a new unit.
Yes — filters, coils, drains, belts and bearings, and the airflow measured against the design duty, on an interval that suits the plant and the building. Commercial maintenance is quoted on the site rather than priced from a table, because the number of units, the access and the filter types vary too much for a published figure to be honest.
Not sure where to start?
Send us a message with what you have noticed at home. We will tell you honestly whether you need a survey, a system, or neither.
Or see what it costs — unlike most in this trade, we publish our prices.
Trained on the systems we install
Certificated — and here they are
Most trade sites show you a row of logos. These are the actual certificates, both sat in August 2026. Tap either one to read it, or download the PDF.
- 12-month workmanship guarantee On top of the manufacturer’s warranty, which we register in your name. If anything we installed fails because of the way we installed it, we come back and put it right. What it covers.
- Company no. 12092552 Registered in England & Wales. Trading as Cavalli Ventilation since July 2019, and in ventilation since 2003.
- Airflow measured on every install A calibrated anemometer at the grille, recorded and handed over. The only figure that counts is the one measured in your room.