A weatherproof FCU is a fan coil unit designed to operate safely in exposed or harsh environments where it may be affected by rain, dust, humidity, wind, or temperature changes. An FCU is an HVAC appliance that uses a fan to blow air across a heating or cooling coil, then delivers the conditioned air into a room or space. The “weatherproof” part means the unit’s casing, electrical components, seals, and sometimes controls are specially protected so moisture and debris cannot easily damage them.

It works by drawing air from the surrounding area, passing it over a coil that contains chilled or hot water from a central plant, and then pushing the conditioned air back out. A thermostat or control system tells the FCU when to turn on, how fast the fan should run, and whether it should cool, heat, or maintain temperature. In weatherproof models, the housing is usually stronger and better sealed, with corrosion-resistant materials and protected wiring to handle outdoor or semi-outdoor installation.

These units are commonly used in areas like balconies, rooftops, plant rooms, loading bays, hotels, or industrial spaces where a standard indoor FCU would not survive. They provide the same basic comfort function as a regular FCU, but with added durability and protection against the elements.

Weatherproof fused connection units can be installed outdoors wherever they are protected by a suitably high IP-rated enclosure and installed in accordance with the manufacturer’s instructions and local electrical regulations. Typical locations include external walls, patios, garages, sheds, workshops, garden buildings, and other exterior areas where they may be exposed to rain, humidity, or splashing.

They are commonly fitted: On the outside wall of a house or outbuilding In sheltered but still outdoor areas, such as under eaves or canopies Near fixed outdoor equipment, like lighting, pumps, heaters, or power for garden appliances In partially exposed utility spaces, provided the unit is rated for the environment

They should not be installed: Where they may be submerged or exposed to flooding In places subject to heavy direct water jets unless specifically rated for that Where physical damage is likely, unless additional protection is provided In enclosed spaces without ventilation if moisture buildup is a concern

For outdoor use, the unit should generally be at least weatherproof and suitable for the specific exposure level, often with an IP rating such as IP55 or higher depending on conditions. It must also be mounted securely, with cable entries sealed properly to prevent water ingress.

If in doubt, installation should be done by a qualified electrician.

A weatherproof FCU should typically have a minimum IP rating of IP65, with IP66 preferred if it will be exposed to heavy rain, hose spray, or harsh outdoor conditions.

In practical terms: IP54/IP55: suitable only for light weather exposure or under a sheltered location. IP65: dust-tight and protected against water jets; this is the most common minimum for outdoor “weatherproof” use. IP66: better protection for stronger water jets and more severe weather. IP67: only needed if there is a risk of temporary immersion.

If the FCU is installed fully outdoors, not under cover, IP65 is usually the safest baseline. If it is in a coastal, industrial, or washdown environment, go for IP66 or higher. Also, make sure the enclosure seals, glands, cable entries, and accessories match the same IP rating; the overall protection is only as good as the weakest part.

So, the short answer is: a weatherproof FCU should generally be at least IP65, and IP66 if more robust protection is needed.

Turn off the circuit at the consumer unit, lock it off if possible, and prove dead with a proper two-pole voltage tester before touching anything. If you are not fully competent with fixed wiring, stop and use a qualified electrician.

For a weatherproof FCU:

1. Isolate power and verify dead at the FCU and the supply.
2. Remove the front carefully and note/photograph the existing wiring.
3. Check the replacement is the correct IP/weatherproof rating and suitable current rating for the cable and load.
4. Connect conductors only to the correct terminals: permanent live in, switched live out (if used), neutral to neutral, and earth to earth. Keep the earth continuous even if the device itself is plastic.
5. Tighten terminals to the manufacturer’s torque; loose connections can overheat.
6. Fit the correct fuse for the appliance/circuit.
7. Ensure cable entries use proper glands or seals so water cannot enter, and maintain the gasket.
8. Reassemble fully, checking no insulation is trapped and the enclosure closes evenly.
9. Restore power and test operation, polarity, and RCD protection.

Important: if there is any sign of heat damage, corrosion, melted insulation, burnt terminals, water ingress, or unknown cable identification, do not reuse the wiring until it is inspected and repaired. Outdoor wiring faults can be dangerous and fire-prone.

A weatherproof FCU (fused connection unit) should be used for appliances or equipment installed outdoors, in damp locations, or anywhere exposed to rain, splashing, or washing down. Typical examples include:

Outdoor lighting circuits Garden lights and security lights Pond pumps and water features External socket-fed appliances Electric gate motors Garage and shed power supplies Outdoor heaters Air-conditioning condenser units Extractor fans in exposed locations Signage and decorative lighting Irrigation and sprinkler controls External CCTV or alarm equipment Roof or loft-mounted plant with outdoor exposure Caravan, workshop, or outbuilding supplies

It is especially suitable where a fixed appliance needs a local isolation point and protection by a fuse, and where the wiring connection must be protected from weather.

A weatherproof FCU should be selected whenever the equipment is: outdoors in a humid or wet environment subject to rain, condensation, or splashing mounted on an external wall used in a garden, yard, or commercial external area

The key reason is safety: the enclosure protects the connection from moisture and dust, while the fuse helps protect the appliance and cable from overload or fault conditions.

If the equipment is portable or plug-in, a normal outdoor-rated socket or weatherproof socket outlet may be more appropriate. For fixed installations, a weatherproof FCU is usually the preferred option.