HFC Series Installation & Operation Manual

About the HFC Series

The HFC series are horizontal concealed fan coil units designed for installation in ceiling voids and loft spaces. They connect to a chilled or heated water circuit from an air source heat pump and deliver conditioned air to the room below via ductwork.

What's Included

Each unit is supplied complete with:

• HFC fan coil unit with 3-row copper heat exchanger
• 200mm plenum box for duct connection
• Washable air filter
• Fan Coil load-compensated controller (mounted on the unit)

The unit is controlled entirely by the Fan Coil load-compensated controller board mounted on the unit. No separate thermostat or remote control is required.

How It Works

1. Chilled (or heated) water from your heat pump flows through the 3-row copper coil inside the unit.
2. The fan draws room air in through the return air box and filter.
3. Air passes over the coil, where heat is exchanged — cooling the air in summer, or warming it in winter.
4. Conditioned air exits through the 200mm plenum and is distributed via ductwork to ceiling vents in the room below.
5. Condensate produced during cooling is collected in the built-in drain tray and exits via the condensate drain connection.

Product Range

Pipe Connection Side

All HFC units can have their pipe connection side switched between left and right on site. See the Installation chapter for instructions. When switched, the cooling and heating capacity correction coefficient is 0.9.

Overview

Every HFC unit ships with a Fan Coil load-compensated controller pre-mounted on the unit.

The controller is located on the fan coil unit itself, in the ceiling void / loft space. It has a small display screen and buttons for configuration.

What the Controller Does

The controller continuously monitors five temperature sensors and uses them to make intelligent decisions about fan operation:

Return Air Temperature and Ceiling Height

The return air temperature sensor measures the air being drawn back into the unit from the room. Because warm air rises, the air at ceiling height will be warmer than the air at head height or floor level where people actually are.

In a typical room with a 2.4m ceiling, the difference is usually 1–2°C. In rooms with higher ceilings, the difference can be greater.

Recommendation: When setting your target temperature, account for this difference. If you want the room to feel like 21°C at head height, you may need to set the controller target to 22–23°C, because the return air at ceiling level will read warmer than the occupied zone below.

The exact offset depends on room height, insulation, and how much the system has been running. Adjust the target based on how the room feels and fine-tune over a few days.

Automatic Operation

The controller detects the operating mode automatically by comparing the water temperature to the loft ambient temperature:

• Cooling mode: When the water flow temperature is significantly below the loft ambient temperature, the controller knows the heat pump is actively producing chilled water and activates cooling.
• Heating mode: When the water flow temperature is significantly above the loft ambient temperature, the controller activates heating. Heating mode can be disabled in the controller settings if you only want to use the unit for cooling.
• Standby: When the water temperature is close to the loft ambient (heat pump off or in transition), the controller keeps the fan off. This is important in summer — loft temperatures can exceed 40°C, so water sitting idle in pipes will be warm. The controller uses the ambient sensor to recognise this as "no active heating" rather than mistaking it for hot water from the heat pump.

There is no manual seasonal switching. The controller adapts automatically.

Fan Speed Control

The controller drives the fan with variable speed modulation — continuously adjustable between a minimum and maximum speed, not fixed steps. The fan speed is adjusted based on:

• The difference between the target temperature and the current return air temperature
• The water temperature delta (flow vs return)
• The rate of temperature change

This means the fan runs faster when the room is far from target and slows down as it approaches. In cooling mode, as the room nears the target temperature, the fan will reduce to its minimum speed rather than switching off abruptly — this maintains gentle air circulation and prevents the temperature from bouncing above and below the target. The fan only stops fully when the room is at or below the target temperature.

Customer Settings

The controller is configured via the display and buttons on the unit. The primary settings are:

Example: With a target of 21°C and a threshold of 1°C in cooling mode, the fan will activate when the return air temperature exceeds 22°C and will modulate down as the return air approaches 21°C.

Accessing the Controller

The controller is mounted on the fan coil unit in the loft / ceiling void. To adjust settings:

1. Access the ceiling void via the loft hatch or access panel.
2. Locate the controller on the fan coil unit — it has a small illuminated display.
3. Use the buttons to navigate the menu and adjust settings.
4. Settings are saved immediately and persist through power cycles.

Future connectivity: Modbus support is planned for a future firmware update, allowing integration with building management systems and smart home platforms.

Load Compensation

Traditional fan coil controllers run the fan at a fixed speed regardless of conditions. The Fan Coil load-compensated controller is different — it continuously measures the actual cooling (or heating) load and adjusts the fan output to match.

What this means in practice:

• The controller monitors the water flow and return temperatures to calculate the available cooling/heating energy from the heat pump.
• It monitors the air supply and return temperatures to calculate the actual room demand.
• It combines these to determine how hard the fan needs to work right now.

Example — cooling mode:

The result is that the unit only uses the energy it needs. Less noise, less electricity, and the room stays at a stable temperature without the on/off cycling of a traditional thermostat.

The customer sets their target temperature and threshold once. The controller handles everything else automatically.

Float Switch Input (Optional)

The controller has an optional float switch input for condensate overflow protection. A float switch can be installed in the condensate drain tray or drain line.

How it works:

• When the float switch circuit is open (normal operation), the unit operates normally.
• When the float switch circuit is closed (condensate level too high — drain is blocked or overwhelmed), the controller will:
  1. Stop the fan immediately
  2. Sound an audible buzzer alarm

Important: The float switch will not prevent all condensation. When the fan stops, the chilled water coil will still be cold and condensation will continue to form on the coil surface until the water circuit is isolated or the water warms up. The float switch limits the amount of condensate produced by stopping the fan, but it is not a substitute for a properly installed and maintained condensate drain.

If the float switch alarm activates:

1. Check the condensate drain for blockages and clear if necessary.
2. Empty any accumulated water from the drain tray.
3. Once the drain is clear and the float switch resets (circuit opens), the controller will resume normal operation automatically.

Before You Start

• Read the safety warnings chapter in full
• Verify the unit model matches the design specification
• Check the unit for transport damage — inspect the coil fins, fan, drain tray, and controller
• Confirm the ceiling void / loft has adequate space for the unit plus service access
• Confirm the structure can support the unit weight (14–19 kg plus water in coil)
• Confirm chilled/heated water pipework is available at the installation location
• Confirm a suitable electrical supply (230V / 50Hz / fused spur) is available
• Confirm a condensate drain route is available (gravity or separate pump)
• Confirm 200mm ductwork route from plenum to ceiling vent is planned

Tools Required

• Drill and fixings for ceiling void suspension
• Spirit level
• Pipe wrenches / adjustable spanners
• PTFE tape (for BSP threaded connections)
• Screwdrivers (Phillips and flat)
• Wire strippers
• Multimeter
• Tape measure

Materials Required (Not Included)

• Threaded rod, channel, and fixings for suspension (rated for unit weight + water)
• ¾″ BSP isolation valves × 2 (flow and return)
• Strainer filter (if not already fitted to the system)
• Magnetic filter (if not already fitted to the system)
• ¾″ BSP flexible hoses or copper pipe with fittings
• Closed-cell pipe insulation (Armaflex, Kaiflex, or equivalent) — minimum 13mm wall, 19mm recommended for loft spaces. Do not use mineral wool or fibreglass. Include insulation for all valves and fittings.
• Insulation adhesive and compatible tape for sealing all joints
• 200mm insulated flexible duct
• 200mm ceiling vent grille(s)
• 200mm duct clamps (2 per duct run)
• Condensate drain pipe (or separate condensate pump if gravity drain not possible)
• Anti-vibration mounts / rubber isolator hangers
• Float switch for condensate overflow protection (optional but recommended)
• Electrical cable (fused spur to unit)

1. Mount the Unit

The unit must be hung from the ceiling rafters or joists. Do not mount from plasterboard or lightweight battens.

Before mounting, check the joist loading:

Check that the joists or rafters at the mounting location can support the total suspended weight. If the mounting point spans between joists, use a noggin or cross-brace to distribute the load.

Installation steps:

1. Choose the mounting position in the ceiling void. The unit should be level and accessible for future service (controller access, filter changes).
2. Install threaded rod or channel hangers from the ceiling rafters/joists.
3. Use anti-vibration mounts (rubber isolators or anti-vibration hangers) between the fixings and the unit. This prevents fan vibration from transmitting through the ceiling structure into the room below. Without anti-vibration mounts, low-frequency hum may be audible in the room.
4. The unit must be installed level. Use a spirit level on the drain tray. A slight tilt toward the condensate drain (1–2°) is acceptable to assist drainage.
5. After mounting, check all fixings are secure and the unit does not rock or sway.

Minimum clearances:

• Above: 50 mm for air circulation
• Below: sufficient for filter access and controller access
• Return air side: do not obstruct — this is where room air enters
• Plenum side: clear path for 200mm duct connection

2. Connect Water Pipework

1. Verify water filtration is installed. A strainer filter and magnetic filter must be fitted on the system (typically on the return, upstream of the heat pump). These protect the coil from debris and magnetite. This is a warranty requirement.
2. Identify the flow and return connections on the unit — ¾″ BSP internal thread.
3. Install isolation valves on both flow and return pipes.
4. Connect pipework using PTFE tape on all threaded joints.
5. Insulate ALL chilled water pipework with closed-cell insulation (Armaflex, Kaiflex, or equivalent). This includes every pipe run, valve, fitting, tee, elbow, and hose connection. Seal all insulation joints with adhesive or compatible tape. Any exposed cold surface will condensate and drip. Do not use mineral wool or fibreglass insulation — only closed-cell. Refer to the "CRITICAL: Pipework Insulation" section in the Safety Warnings chapter for full requirements.
6. Pressure test the system to 1.5× working pressure before commissioning. Check for leaks at all joints.

3. Connect Condensate Drain

1. The condensate drain is a ¾″ BSP external thread connection on the built-in drain tray.
2. Route the condensate pipe to a suitable drain point — internal waste pipe, external drain, or a separate condensate pump.
3. If using gravity drainage, the pipe must fall continuously at minimum 1:50 gradient.
4. Do not reduce the pipe diameter below the drain connection size.

Warning: The unit will produce condensate whenever operating in cooling mode. Failure to connect the condensate drain will result in water damage.

4. Connect Ductwork

1. Attach 200mm insulated flexible duct to the plenum box.
2. Secure with a 200mm duct clamp at each end (plenum and ceiling vent).
3. Keep duct runs as short and straight as possible — every bend reduces airflow.
4. Insulate the duct to prevent condensation when carrying cold air.
5. Install the 200mm ceiling vent grille in the room below.

5. Electrical Connection

1. Disconnect the electrical supply before making any connections.
2. The unit requires 230V / 50Hz via a fused spur or isolator switch (3A fuse is sufficient for all models).
3. Open the electrical connection box on the unit.
4. Connect Live (brown), Neutral (blue), and Earth (green/yellow) to the terminal block.
5. Close the connection box and secure all cable glands.
6. The Fan Coil controller is pre-wired to the fan motor — no additional wiring is needed for the controller.

All electrical work must comply with BS 7671 (IET Wiring Regulations).

6. Changing Pipe Connection Side

The unit ships with pipe connections on one side. To change to the other side:

1. Remove the centrifugal fan, cover plate, and electrical box screws.
2. Move the side plate at the air outlet to the other side.
3. Rotate the fan assembly and cover plate 180° and refix.
4. Move the electrical box to the other side and refix.

When the pipe side is switched, the correction coefficient for both cooling and heating capacity is 0.9.

Pre-Commissioning Checks

Before switching on for the first time:

1. Water system: System is filled, pressurised, and leak-free. All isolation valves are open.
2. Condensate drain: Drain is connected and tested (see drain flow test below).
3. Ductwork: All ducts connected and clamped. Ceiling vent(s) installed.
4. Electrical: All connections secure. Earth connected. Fused spur is OFF.
5. Filter: Filter is installed in the return air box.
6. Clearances: Nothing is resting on or obstructing the unit, ducts, or return air path.
7. Controller: The Fan Coil controller display is visible and undamaged.

First Start

1. Switch on the electrical supply at the fused spur.
2. The controller display will illuminate and show the current sensor readings.
3. Set the target temperature and threshold on the controller (default: 21°C target, 1°C threshold).
4. If the heat pump is producing chilled or heated water, the controller will detect this and activate the fan automatically.
5. Verify air is flowing from the ceiling vent(s).
6. Check for unusual noise or vibration.

Condensate Drain Flow Test

This test is mandatory before commissioning and is required for warranty registration.

Why This Matters

In cooling mode, the unit removes moisture from the air. On a hot, humid day this can produce a significant amount of water. If the drain cannot keep up, the tray overflows and water damages the ceiling below.

Worst-Case Condensate Production

The following rates are calculated for extreme UK conditions (27°C, 80% relative humidity — a very muggy day with windows open):

The Test

Pour the following amount of water into the drain tray in one go and verify it drains completely within 60 seconds:

If multiple fan coil units share a common condensate drain line, the drain must be able to handle the combined output of all units running simultaneously at full capacity. Test with the combined volume.

Pass / Fail

• Pass: Water drains completely within 60 seconds. No leaks at any joint.
• Fail: Water pools, drains slowly, or leaks. Do not commission the unit. Re-route or increase the drain pipe diameter, increase the gradient, or clear any blockage. Re-test.

Record the test result when submitting installation photographs for warranty registration.

Post-Start Checks (after 10 minutes)

• Air temperature at the supply vent should be noticeably cooler (or warmer) than the room
• Water flow pipe should feel cold (cooling) or hot (heating)
• Water return pipe should be slightly warmer than flow (cooling) or cooler (heating)
• Condensate is draining (in cooling mode — may take a few minutes to begin)
• No water leaks at any pipe joints
• Controller display shows sensible temperature readings on all 5 sensors

Record Keeping

Record the commissioning date, installer details, and sensor readings for the property records.

Day-to-Day Use

The HFC unit is designed for fully automatic operation. Once commissioned:

1. Set your target temperature on the controller (accessed in the loft). For example, 21°C.
2. Set your threshold — the temperature difference before the fan activates. For example, 1°C means the fan starts when the room is 1°C above target in cooling mode.
3. That's it. The controller handles everything else automatically.

The controller detects whether the heat pump is producing chilled water (cooling) or heated water (heating) and adjusts accordingly. No manual seasonal switching is required.

What the Controller Does Automatically

Adjusting Settings

To change the target temperature or threshold:

1. Access the unit in the loft / ceiling void.
2. Use the buttons on the controller to navigate the settings menu.
3. Adjust the target temperature or threshold as needed.
4. Settings save immediately.

When the Unit is Not in Use

If the unit won't be used for an extended period:

1. Switch off at the fused spur.
2. Close the isolation valves on the water connections.
3. Leave the filter in place to prevent dust entering the unit.
4. When restarting, open isolation valves and verify system pressure before switching on.

Maintenance Schedule

Cleaning the Filter

The filter is washable and reusable. How often you need to clean it depends on the room the unit serves:

How to Clean

1. Switch off the unit at the fused spur.
2. Access the unit in the loft / ceiling void.
3. Slide out the filter.
4. Wash under running water. Use a mild detergent if needed. Do not use hot water — it can damage the filter media.
5. Allow to dry completely before refitting. Do not refit a wet filter.
6. Slide the filter back in and check it sits flush.

A blocked filter is the most common cause of poor performance. It reduces airflow, increases energy consumption, can cause the coil to ice up in cooling mode, and makes the fan work harder (increasing noise). If performance drops, check the filter first.

Cleaning the Condensate Drain

1. Switch off the unit.
2. Locate the condensate drain connection.
3. Disconnect the drain pipe if accessible.
4. Flush with clean water to clear any algae or debris.
5. Reconnect and verify the drain flows freely.

Coil Cleaning

The coil can be cleaned with a soft brush or compressed air at low pressure. Do not use sharp objects or high-pressure water — the aluminium fins are fragile and bending them reduces performance.

Do Not

• Operate the unit without a filter installed
• Spray water directly into the unit or onto electrical components / controller
• Block the return air inlet or supply air outlet
• Hang anything from the unit
• Attempt to repair electrical components or the controller yourself

Common Issues

Controller Sensor Readings

If the controller display shows temperature readings that seem wrong:

• Water flow/return both at ambient: Heat pump is off or not circulating. This is normal when the system is idle.
• Air supply and return identical: Fan may not be running, or duct is disconnected.
• Loft temp very high: Normal in summer. The controller accounts for this.

For any persistent issue, contact Fan Coil at hello@fancoil.co.uk with:

• Your unit model and order reference
• The sensor readings shown on the controller display
• A description of the issue