FAN COIL UNIT | Installation Guideline

Installing a fan coil unit, just looks like putting a galvanized box up in the ceiling and having it rattled out in a couple of hours. Be great if this was the truth…

In our below article we will cover the stages and integrations to deliver, inspect, accept, install, connect and commission a horizontal and vertical type unit.

So… How do fan coils work?

Firstly if you want to understand how fan coil units work, we have written an article you may be interested in ‘Fan Coil Units | What, Where & How’.

Accepting delivery and taking responsibility

The first stage of the installation will be taking for the company that is purchasing the units to take responsibility.

This will consist of taking delivery of the equipment, completing the relevant inspections to accept that it is in good condition, not damaged, correct and complete.

Once the equipment has been inspected, it will be moved to storage, in a specific area or close to where the installation will take place.

Delivery inspection checklist

In order to complete a successful delivery check, the following documents will be needed:

• Delivery Checklist [as per below]
• Copy of order and equipment list that was sent to the supplier to order the equipment
• Copy of the delivery ticket from the logistics company, that clearly details all equipment, ancillaries and spares that were ordered.

Any damage or issues should be photographed, documented, and sent to the supplier/logistics company.

Ref	Inspection/Task	Status [yes/no/n/a]	Notes
1	A supplier’s consolidated delivery ticket is available, showing all equipment and ancillaries for inspection and being used to check against.
2	A copy of the original order that was sent to the supplier is available for reference and is used to check against.
3	Fan Coil Units are packaged and crated in separate boxes, for maximum protection.
4	Protection is dry
5	Unit is dry
6	The external casing of the unit is undamaged
7	Unit nameplate and details match the order
8	Any frames are included
9	Connections for ducting are correct
10	The drain pan for condensate is not bent or damaged.
11	The unit does not have anything loose [rattle]
12	Pipework connections are the undamaged and correct size
13	Inspect all handings of pipework to ensure correct side [right or left]
14	Electrical connections are undamaged.
15	Ensure all access doors have latches or the correct amount of fastenings.
16	Remove the access panel of the unit and inspect the interior
17	Spin the fan of each FCU to ensure not out of line, which would suggest damage in transit.
18	Check each cooling coil for damage
19	Check each heating coil for damage
20	Sensors, valves, control valves, control valve actuators, and ancillaries, where required, are packaged within each individual fan coil unit, or separately.
21	Filters are available and clean
22	Spare filters supplied as per order
23	All general spares have been supplied [these will be handed over to the facilities department on completion of the project

Storage

Once the equipment has been accepted it, would usually be put into onsite storage awaiting installation.

The storage would usually be a separate, dedicated area within the project/close to where the installation will take place.

Usually, the units will be manufactured and rated only for internal use. The storage should be as a minimum:

• Internal
• Well covered and protected [be wary of using plastic as can cause condensation]
• Raised off of the ground to allow air flow
• Flat
• Dry
• Well ventilated
• Clean
• Dust free
• Out any potential weather

Once place the units should be protected to reduce the risk and stop any potential damage happening on site.

Also, units should, to reduce the risk of damage:

• Not be stacked
• Have materials stacked on them

Ensure that any filters and ancillaries are well protected, and stored so as will not be easily lost or damaged.

Preparing for the installation

Prior to the installation, there will be some site preparation works that will be needed, these have been listed below:

Ref	Task
1	Check and ensure that the structure can support the weight of the FCU, any ducting, and ancillaries. The weights for the units can usually be found in the manufacturer’s literature. Ancillaries and ducting from the contractors installing them.
2	Review the local fire codes to ensure that, if using ceiling-mounted/concealed, all precautions are taken with regards to using voids as return air paths.
3	Ensure that there will be enough space to install the unit, ducting, pipework, valves, electrics, dampers, and ancillaries necessary to operate.
4	Ensure that the pipework handing [left side or right side] is correct
5	Check that the space required for any future maintenance will be available [replacement of filters, coils, fans, strainers, etc…]. The requirements can usually be found within the manufacturer’s literature.
6	Review the space available for the condensate to ‘fall’ is adequate and it will not interfere with the ceiling.
7	Confirm that all services will be supported independently by the FCU.
8	Ensure that the fixings being used to hang the services are adequate for the structure.
9	If using a floor-mounted unit, ensure that the base is adequate and flat

Maintenance and access spacing requirements

The below dimensions are provided as a guide to understand when installing the unit what the maintenance requirements could be, refer to the specific manufacturer’s information for your specific project.

Type of Unit	Front	Back	Sides	Top	Bottom
Vertical Cabinet	3 in. / 75 mm	n/a	12 in. / 305 mm	24 in. / 610 mm	n/a
Vertical Concealed	36 in. / 915 mm	n/a	8.5 in. / 216 mm	24 in. / 610 mm	n/a
Horizontal Cabinet	24 in. / 610 mm	n/a	12 in. / 305 mm	n/a	28 in. / 711 mm
Horizontal Concealed	24 in. / 610 mm	n/a	8.5 in. / 216 mm	n/a	28 in. / 711 mm

How long does it take to install a fan coil unit?

This will depend on how good and experienced the engineer is…

Generally, for a full installation, FCU, ducts, grilles, pipework, etc. would expect from 1-2 days.

Installation of fan coil unit

The below fan coil unit installation guide will detail how to install a single hydronic fan coil system within a commercial building [office]; they can also easily be installed or within residential, hotels, and industrial buildings.

Prior to the installation taking place, there would be an onsite check completed to make sure that the unit is undamaged, correct and the area is ready to install.

It is usually a good idea to do this prior to removing it from the site storage area.

Installation checklist for FCU

If any issues are found then an evaluation should be conducted to understand if they will impact the installation of the unit. All should be photographed and documented prior to moving the unit.

Ref	Inspection/Task	Status [Yes/No/n/a]
1	Check the information on the nameplate of the unit to ensure it is the correct equipment for the location to be installed
2	Check to make sure all ancillaries are with the unit [Sensors, valves, control valves, control valve actuator, filters]
3	Pipework connections 2 pipe / 4 pipe are ok and not damaged
4	Pipework handings [left/right] are correct and in line with the site piping installation
5	Unit is not dented or damaged
6	Unit is dry externally and internally
7	Unit is clean internally and externally
8	There is no mold inside the unit
9	Spin the fan to ensure not out of line
10	Check the condition of the cooling coil to ensure not damaged
11	Check the condition of the heating coil to ensure not damaged
12	FCU plenums are available and undamaged
13	All required grilles are available and undamaged [supply and extract/recirculation]
14	Any silencers/attenuators are available, dry and undamaged
15	All ducting and flexible ducting is ready and undamaged
16	All hangers and supports available

General Site installation checklist

If any issues are found then an evaluation should be conducted to understand if they will impact the installation of the unit. All should be photographed and documented prior to moving the unit.

Ref	Inspection/Test	Status [Yes/No/n/a]
1	The ceiling grid has been removed and access is sufficient to install the unit. This includes all required pipework and ductwork
2	There is no damage around the ceiling in the area where the unit will be installed
3	The floor, where will be working, is flat and clear, and unobstructed for access equipment.
4	There is sufficient space in the ceiling void [depth] to allow installation of the FCU
5	There is sufficient space in the ceiling void [depth] to allow the installation of the grilles and grille boxes.

Site services installation checklist

If any issues are found then an evaluation should be conducted to understand if they will impact the installation of the unit. All should be photographed and documented prior to moving the unit.

Ref	Inspection/Test	Status [Yes/No/n/a]
1	Chilled water flow and return pipework is installed to allow connecting of the unit, including all valves, strainers, temperature pockets, gauges, draincocks, commissioning stations, and control valves/actuator where required.
2	Heating/hot water flow and return pipework is installed to allow connecting of the unit, including all valves, strainers, temperature pockets, gauges, draincocks, commissioning stations, and control valves/actuator where required.
3	Condenser water pipework is installed to allow connecting of the unit.
4	The fresh air supply is available and ready for connecting
5	Electrical cabling is installed complete with an emergency stop / electrical disconnect ready for final connection of FCU general power and electric heater if being used
6	BMS and controls cabling installed and ready for connecting.

Once all the checks have been completed, and no major issues noted that would impact the installation, the unit should be moved into a position ready for installation.

Installing and hanging a vertical FCU

Vertical units should obviously be installed.. vertically.

Below are some common steps that will need to be taken to install the unit.

Ref	Task
1	The FCU will usually be manufactured with some ‘lugs’ that will be used to fix the unit to the wall bracket or directly to the wall, ensure that these are available
2	Any holes and openings, especially any external intakes, to the wall should be prepared prior to installation, use the manufacturer’s information [material submission] to understand what is expected.
3	Offer up the unit to the wall/space where being installed.
4	Any legs that can be adjusted should be to level the unit correctly.
5	The unit now should be in place [but not fixed]. Mark the locations of the unit hangers on the wall and make sure are in accordance with the unit literature/dimensions. Ensure the markings are level.
6	Remove the unit so that the markings are visible and a hole can be made
7	Make the holes where marked in the wall, size will need to be in line with manufacturers literature, but generally will be as per the bolt/coach screw/lag screw/stud/threaded rods and fixings being used.
8	Insert the fixings into the holes that have been made
9	Time to now install the unit
10	Remove any panels to allow installation [check manufacturers literature]
11	Move the unit into position and line up the lugs with the fixings that were installed into the wall
12	Lower the unit onto the fixings so that they now support the weight
13	Move to the below sections relating to the pipework, valves, insulation, condensate, electrics, BMS, sensors, and commissioning.

Installing and hanging ta horizontal FCU

Horizontal units should obviously be installed.. horizontally.

Below are some common steps that will need to be taken to install the unit.

Ref	Task
1	The FCU will usually be manufactured with some ‘lugs’ that will be used to fix the unit to the wall bracket or directly to the wall, ensure that these are available
2	The unit will generally be installed in an accessible ceiling void and ceiling hung from a slab and or secondary steelwork.
3	Any holes and openings that are required in the ceiling, should be prepared, after inspection above, prior to installation. Use the manufacturer’s information [material submission] to understand what is expected.
4	The most common way to hang the unit, which provides a lot of flexibility, is to hang from a unistruct frame that allows adjustment horizontally and vertically. This allows aligning up to any services and, where required ceiling grids.
5	Remove any panels to allow installation [check manufacturers literature]
6	Move the unit into position and line up the lugs with the fixings that are installed
7	Lift the unit so that the fixings come down through the lugs and fix them so are supporting the weight.
8	Level the unit but ensure that the condensate tray has a fall to allow the condensate to drain away. The rule of thumb is 25mm [1 inch] per 3000mm [10 feet] of pipe from the FCU.

Ductwork connections

Usually, there will be no need for ductwork connections to a vertical-type unit installation. They will be predominantly for the horizontal ceiling type unit.

There will potentially be 3 types of duct connections:

1. Fresh air connection from a central AHU system (small % used in relation to the overall FCU flow rate)
2. Recirculation connection bringing air from the space back to the FCU to recondition
3. Supply air to serve the conditioned air to the space

Exhaust air will usually be managed by a separate exhaust air system that will remove the quantity of air/ airflow rate that is being introduced via the fresh air system and any potential losses via infiltration.

Fresh air ventilation & recirculation air ductwork connection

Fan coil units will usually incorporate the ability to be fed with fresh air from a central plant air handling system or directly via connection to a fresh air intake duct and external louver.

The reason to ensure the correct fresh air volume is supplied is to provide the occupants with clean air diluting any buildup of carbon dioxide and maintaining the indoor air quality that is needed for commercial spaces, industrial spaces, and also some residential buildings under certain building codes/fresh air ventilation codes and regulations.

There are 2 ways of supplying fresh air to the unit:

1. Galvanised ducting connected directly to the FCU, when a return air plenum is used
2. Galvanised ducting not connected to the FCU but directing the fresh air directly into the back of the unit, when a return air plenum is not used.

In each instance the air volume flow rates will be controlled via dampers [VCD], to ensure the correct conditions are met.

Below are some common steps that will need to be taken to install the unit for each scenario. 

Using a plenum connected to the FCU

In many situations the FCU, if being connected to a return air grille, will be supplied with a plenum. This is to allow the fresh air and recirculated air to be connected to the unit.

Below are some tips on how to connect them both:

Ref	Task
1	Before final connection, ensure that the fresh air ventilation ductwork has been inspected and installation approved including all fire dampers, etc by the relevant consultant.
2	Inspect the galvanized plenum to ensure no damage or issues.
3	Install the fresh air plenum onto the FCU
4	The fresh air/return air plenum should have a hole/duct stub/collar of the same size as the fresh air duct that is to be connected.
5	Review the drawings to understand the duct layout, duct size, and if there are any requirements for a volume control damper [VCD] to be installed in the duct to allow control and setting of the airflow rate/volume during the commissioning stage.
6	Manufacturers recommend, and it is good practice, that the ducting is installed in a straight line for a minimum of 3 fan diameters from the unit, volume control dampers and devices should be installed
7	Install the plenum, ducting, and components including the flexible duct for the final connection between the fresh air supply and unit. The ducting would usually be made from galvanized sheet metal.
8	Install the ductwork from the FCU plenum to the recirculation air grille and connect with flexible ducting to mitigate any vibration transfer to the ceiling.
9	The ducts are usually connected/fastened with sheet metal screws/clamps and some form of duct mastic/cement purposefully manufactured for the application.
10	Once the complete move to the pipework, insulation, controls, and commissioning below.

Not using a return air plenum

If there is no requirement for a hard return duct connection to be used between the FCU and the return air grille, there will usually not be a requirement to use a return air plenum [using the ceiling as one instead].

In this instance, the fresh air duct will be positioned close to the FCU intake where it will blow into the back of the unit, and a grille will be installed in the ceiling, allowing the air to transfer between the conditioned space and the unit for recirculation.

Ref	Task
1	Ensure that the return air grille is installed with a damper
2	Ensure that the fresh air supply to the unit is within 50mm of the filter/intake, to ensure that the air is blown where needed.

Fan coil supply air installation

To allow the transfer of conditioned air from the FCU into the space, there will usually be a requirement for supply air ductwork to be installed.

A supply air plenum will be installed onto the front of the FCU, which can have from 1 to 6 spigots to connect out to supply air grilles, depending on the design requirements.

Below are some common steps to install the ducting needed.

Ref	Task
1	Review the drawings to understand the duct layout, duct size, and if there are any requirements for volume control dampers [VCD], fire dampers, or control dampers to be installed within the ducting.
2	Inspect the galvanized supply air plenum to ensure no damage or issues, that are to be connected to the FCU.
3	Install the supply air plenum onto the FCU
4	The plenum should have spigots installed to connect out, via ducting to the grilles.
5	Install the spiral galvanized ducting, or rectangular if needed, connecting to the supply air plenum out to the location of the supply air grilles/linear diffusers. Use brackets and fixings as per requirements.
6	Manufacturers recommend, and it is good practice, that the ducting is installed in a straight line for a minimum of 3 fan diameters from the unit, volume control dampers and devices should be installed.
7	Connect the ducting to the supply diffusers, by flexible ducting, the grilles will usually have a plenum box fitted to allow the spiral connection and to stop the air from jetting if connected directly to the grille.
8	The ducts are usually connected/fastened with sheet metal screws/clamps and some form of duct mastic/cement purposefully manufactured for the application.
9	Once complete, move to the pipework, insulation, controls, and commissioning below.

Ductwork insulation

To ensure that the vapor barrier is maintained, condensation does not form on the cold surfaces of the installation, there is no cold bridging and the energy efficiency/utility bills are managed, the supply air from the FCU should be insulated.

In some instances, the return air should be as well.

The types of duct insulation product commonly used would be one of the following:

• Mineral wool insulation [wrap/blanket]
• Foam
• Fiberglass insulation [wrap/blanket]
• Insulation board [stiff]

The insulation should be installed onto the ductwork using the appropriate fixings and fasteners such as:

• Pins
• Wrap
• Foil tape / duct tape 
• Chicken wire
• Wire

Flex duct that joins the main ducting to the grilles, if the correct product is purchased, would usually be lined and already incorporate insulation.

Field Pipework installation & valve configurations

Once the FCU has been installed and connected to the ducting, the next step is to connect the pipework [chilled water/heating water]. Commonly there are 2 types of FCU pipework configurations:

• Two pipe fan coil unit 
• Four pipe fan coil unit

Two pipe fan coil units will only have one ‘wet coil’ usually the cooling coil, and maybe if the option is selected and design requires an electric heater element. One set of flow and return pipework.

A four-pipe fan coil unit will have both a ‘wet’ chilled/cold water coil and a ‘wet’ hot water coil. Two sets of flow and return pipework.

In both instances the following sequence of works can be conducted for installing:

Ref	Task
1	Review the drawings to understand the pipework layout, pipework size, and valves/ancillaries that will be required to be installed.
2	Before final connection, ensure that the pipework has been inspected and installation approved by the relevant consultant.
3	Ensure have all the correct tools and materials/pipework/ancillaries.
4	The FCU manufacturer may supply valves, fitting and control valves, etc, to ensure they are correct and available
	Remove the condensate drip pan, this is so that solder can’t get into the pan and less risk of damage
5	Using the correct brackets, install the pipework up to the FCU with only final connections being required, be careful that do not to obstruct the condensate pipework and drip pan that is to be installed later…
6	Once complete, using flexible connections, connect to the FCU the flow and return pipework.  Ensure to keep the valves closed as the Fan Coil unit will need to be pressure tested, flushed, and backflushed.
7	Reinstall the drip pan.
8	Move to pipework insulation

Pipework insulation

Similar to the ducting the pipework will need to be insulated to ensure that the vapor barrier is maintained, condensation does not form on the cold surfaces of the installation, there is no cold bridging and the energy efficiency/utility bills are managed.

The types of pipework insulation commonly used would be one of the following:

• Mineral wool insulation [moulded]
• Fiberglass insulation [moulded]
• Insulation board [stiff but moulded]

The insulation should be installed onto the pipework using the appropriate fixings and fasteners such as:

• Foil tape / duct tape
• Wire

Connecting to electrical heater battery

If there is an electrical heater battery being installed instead of a ‘wet’ coil, then the power circuits should be wired, fully tested, and set up.

Installation of condensate drainage

The condensate drain pan and pipework should be installed, this will be for horizontal and vertical units.

Vertical units may have a condensate pump that would need electrical wiring and set up.

The main thing to think about here is the fall of the pipework from the drain pan to the main condensate collection/discharge point.

Just make sure, after a few meters the pipework is not hanging out of the ceiling…

Flushing and cleaning of the Fan Coil Unit

During the pipework installation, we noted that the valves on the pipework should not be opened until the FCU had been flushed and cleaned. This is to remove any contaminants from the units that are leftover from the installation and manufacturing process.

We need to be careful as the FCU can sometimes need to be integrated into the existing systems, and although one may not be an issue it would not take many to cause issues with the water quality, so just better to prove did something.

So how do you flush a fan coil unit?, lucky, this is quite a simple exercise, and we would use the ‘backflushing technique’, detailed below:

Ref	Task
1	Ensure the equipment is isolated with the bypass closed.
2	Have a bucket available to collect water and hose.
3	Connect one hose to the supply drain cock and to the bucket
4	Connect one hose to the return drain cock and to the bucket
5	Ensuring the return isolation valve is closed, open the flow isolation valve
6	Open the drain cock on the return, allow the water to flow into a bucket for 30 seconds
7	Close the drain cock, close the flow isolation valve
8	Open the return valve
9	Open the flow drain cock, allow the water to flow into a bucket for 30 seconds
10	Drain till visibly clear, complete, close all drain cocks and valves
11	Inspect strainer cleanliness and clean if required
12	All done…Log and record

Electrical connections and disconnect/emergency stops

Don’t forget that the installation will require an emergency stop for the unit to be installed and operating.

Tend to get a few questions when it comes to this subject…

The first and most important is ‘Does a fan coil need a disconnect/emergency stop?‘ – the short answer is Yes to be in line with code requirements. 

Then the next question will be ‘How high can you mount a disconnect/emergency stop?‘ – the answer for this is that the disconnect/emergency stop should be installed in a position that if an engineer is working/maintaining the equipment, and needs to switch it off under emergency conditions it is easily reachable, we would suggest as close as possible to the unit and within quick hands reach.

A couple of others are noted as ‘Can I use a breaker as a disconnect/emergency stop & does a switch count as a disconnect/emergency stop?’, the answer is No. There are specific code requirements for how an emergency stop is manufactured and colored. Generally should be the push-button type, with yellow housing and red button.

Installation of controller, thermostat and fan speed control

Install all controls, this will generally consist of a wall-mounted / duct-mounted sensor [temperature] connected to the BMS / control valves to control the condition within the space.

BMS Alarms and points

 The approved BMS points list for the project should be reviewed to understand what points should be connected and reported. If there is no points list the below can be used as a guide:

• Room temperature,
• High-temperature alarms,
• Temperature setpoints,
• On/Off status,
• Speed control status, low, medium, high,
• Modulating valve control

Noise Levels

As long as the installation of the unit is correct, there should be no issues with the noise levels generated, if there are then this should be reviewed and rectified.

Commissioning of the installation

To ensure the maximum benefit and efficiency from the system, ensuring occupant comfort it should be fully tested, commissioned, and set up in line with the project/commissioning/manufacturers requirements.

Occupant comfort is paramount to ensure minimal complaints are received by the facilities team/building operator.

To understand more about how to commission a fan coil unit, you can check out our article ‘Fan Coil Unit | Onsite Functional Testing Procedure‘

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