Types of Directly Connected Flue Fans: Exodraft, FlueBoost.

Directly connected flue fans, sometimes called draft inducers or chimney fans, are used to assist the
movement of combustion gases when natural draft alone is not sufficient e.g. for Fans For Wood Fired Pizza Oven Exhausts They are commonly used on
commercial, industrial and specialist appliances where flue height, route, building layout or appliance
characteristics make draft support necessary.

This guide explains the main types of directly connected flue fans, including well-known systems such as
Exodraft and FlueBoost, and outlines where they are typically used and what factors installers consider
when selecting a suitable fan.

What Is a Directly Connected Flue Fan?

A directly connected flue fan is a mechanical device installed in the flue system to create, stabilise or
regulate draft. Unlike roof-mounted chimney fans that sit at the termination, directly connected fans
are installed within the flue run itself or onto the appliance connection point, depending on the model.

Their purpose is to support correct operation of the appliance by helping control the movement of
combustion products. The system is selected and installed according to manufacturer instructions,
appliance requirements and applicable regulations.

Why Direct Draft Support May Be Needed

There are several reasons why a commercial or industrial flue installation may require mechanical draft:

Restricted flue height or lack of vertical rise.
Long horizontal sections or multiple direction changes.
Buildings with complex internal routes or multiple floors.
Appliances that require controlled or consistent draft conditions.
Situations where maintaining stable pressure is essential for safe operation.

A directly connected flue fan can help overcome these constraints by providing a controlled flow
of flue gases through the system.

Main Types of Directly Connected Flue Fans

The market includes several types of in-line or directly mounted fans. The two best-known families in the UK
commercial sector are Exodraft and FlueBoost, each offering fans designed for different appliance types
and operating conditions.

Exodraft In-Line & Directly Connected Fans

Exodraft manufactures a range of flue fans designed for both negative-pressure and positive-pressure
applications. While the exact performance characteristics vary by model, Exodraft’s directly connected
solutions generally fall into categories such as:

1. In-Line Draft Generators

These are installed directly into the flue pipe and are designed to support flue gas movement
throughout the system. They may be used in:

Commercial boiler systems.
Condensing or non-condensing appliances (subject to model suitability).
Flue routes with limited natural draft potential.

In-line systems help stabilise conditions across the whole flue rather than only at the terminal.

2. Direct Appliance-Mounted Fans

Some Exodraft units are designed to mount directly at the appliance outlet. These provide controlled
extraction at the source, which can be useful in applications where pressure control at the connection
point is essential.

3. Controlled Draft Systems

Certain Exodraft fans can be paired with control panels that modulate fan speed based on signals such as:

Pressure sensors in the flue.
Temperature sensors.
Appliance demand signals.

This allows stable draft conditions and can support multiple appliances when designed as part of an
integrated system.

FlueBoost Directly Connected Flue Fans

FlueBoost provides a range of flue fans commonly used for gas-fired appliances and certain
commercial applications where additional flue draught is required. Their units are designed to be
directly connected to the appliance or flue, depending on the model.

1. Direct Appliance Connection Fans

These fans are typically used where an appliance requires consistent induced draft at the connection
point. They are normally installed directly onto the appliance outlet or immediately downstream.

Designed for specific categories of gas appliances (subject to model suitability).
Often used where flue height is limited.
Suitable for certain commercial kitchens, water heaters or space heaters.

2. In-Line Induced Draft Fans

FlueBoost also offers in-line systems that form part of the flue run rather than being attached directly
to the appliance. These can support draft over longer or more complex flue routes.

3. Models with Integral Controls

Some FlueBoost units incorporate built-in safety interlocks or are compatible with external control systems,
supporting correct appliance shut-down if the fan is not operating.

Applications for Directly Connected Flue Fans

Draft-assisted installations are found across a wide range of building types and industries. Examples include:

Commercial boilers in plant rooms with limited flue height.
Catering appliances such as commercial ovens and water heaters.
Industrial process heaters.
Installations with complex routing through internal shafts or risers.
Situations requiring stabilised or controlled flue pressure.

The suitability of any specific fan depends on appliance type, flue gas characteristics, pressure category,
installation constraints and the relevant manufacturer instructions.

Key Considerations When Selecting a Directly Connected Flue Fan

Choosing the right fan involves reviewing several factors to ensure compatibility and compliance. Typical considerations include:

Appliance type, category and heat input – to ensure the fan is suitable for that appliance.
Flue gas temperature and pressure regime – different fans are optimised for different conditions.
Required draft level – based on manufacturer requirements.
Flue layout – horizontal runs, height restrictions and number of bends.
Control requirements – such as interlocks, variable speed control or demand-based operation.
Regulatory and safety requirements – depending on building type and appliance class.

A specialist installer will typically carry out a site survey and review appliance documentation to confirm the
correct type of draft support system.

Directly Connected Fans vs Roof-Mounted Chimney Fans

Directly connected flue fans are one category of mechanical draft support. Another common category is the
roof-mounted chimney fan. The main difference is where the fan applies the induced draft:

Directly connected fans create draft within the flue system itself or at the appliance outlet.
Roof-mounted fans create draft at the termination point.

Each method has advantages depending on the appliance, building layout and performance requirements.
Specialist advice ensures the right system is chosen.

Installation & Compliance Overview

Directly connected fans must be installed and commissioned in accordance with:

The fan manufacturer’s installation instructions.
The appliance manufacturer’s flueing and interlock requirements.
Applicable UK regulations and standards for the specific appliance type and fuel.
Project-specific safety and control requirements.

Because directly connected fans influence flue pressure and draft conditions, correct design and
commissioning are essential for safe operation.

When to Use a Specialist Installer

A specialist should be consulted whenever:

A new appliance requires mechanical draft to meet manufacturer specifications.
Flue routes are restricted, unusually long, or involve structural constraints.
Existing systems show signs of poor draft or irregular performance.
Multiple appliances need to share a flue system with controlled pressure conditions.
Fans need to be interlocked with appliance safety systems.

Proper design and installation help ensure compliance, reliable performance and long-term system
stability.

Directly connected flue fans such as those from Exodraft and FlueBoost provide effective solutions
for installations where natural draft alone is insufficient. They support safe, reliable operation of
commercial and industrial appliances by helping control flue gas movement and stabilising conditions
within the chimney or flue.

Choosing the correct fan and control system requires an understanding of appliance requirements,
flue layout, operating conditions and relevant regulations. Engaging knowledgeable flue specialists
ensures the solution is appropriate for the specific project.