Choosing the right extractor fan can be a minefield, with so many different options available, picking the perfect fan that ticks all the boxes can take longer than you would expect. But there is nothing more irritating than choosing the perfect unit only to find out that it is not compatible with your existing wiring! In this article we are going to look at the different styles and functions available and how these options depend on three possible wiring options.
All extractor fans need electricity to run, however, depending on the functionality the wiring can differ.
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The most basic wiring option consists of a Constant Live wire and a Neutral wire to complete the circuit. This requires the fan unit to accommodate some form of built in on/off switching. Options which will work with this type of wiring include fans with built in pull cords, passive infra-red (PIR) movement sensors or humidity triggered sensors (Humidistat).
The next wiring configuration is possibly the most common found in older buildings and can cause issues when looking to upgrade an existing unit. This configuration consists of a Switched Live wire and a Neutral wire. The Switched Live generally will come from the light switch but occasionally it may be attached to a stand-alone switch purely for operating the fan. This means that power will only reach the fan unit when either the lights are turned on or the stand alone switch is operated and the fan will turn off as soon as the lights are turned off or the stand alone switch is deactivated. There are two fan options to use with this wiring configuration which is either a standard/basic on/off fan or you can use a fan with a built in pull cord. This latter option can allow you to control the fan as normal from the light switch when the built in fan pull cord is in the on position, but allows you to also turn the fan off via the built in pull cord which will allow the light to be used without triggering the fan. This can be useful in en suite bathrooms where you want to be able to use the bathroom at night without the noise of the fan disturbing light sleepers.
Finally, the last possible configuration is a three wire option; Switched Live, Constant Live and Neutral. This allows control for the user to trigger the fan but also allows for automatic triggering from outside factors and the ability for the fan to run even when the manual trigger from the switched live is off. Fan options here include Timer function fans that allow fans to continue to run for a set amount of time once the fan is switched “off” and the aforementioned Humidistat fan which allows the fan to be triggered with the light switch but still automatically triggered by humidity as stated before. This allows for the fan to be triggered either as an alternative if the humidity rises from a shower or bath when the light has not been activated, or allowing the fan to stay on longer than the built-in timer has been set for if the humidity level in the room still persists to be higher than the trigger setting.
It is worth having your electrician double check what wiring you have installed already if you are looking at replacing an existing fan, and whether the wiring can be changed to accommodate a different functioning unit if desired. If you are looking at a new install, it is again worth keeping your electrician in the loop in regards to what functionality you desire so your electrician runs in the correct wiring needed. As always, we strongly recommend that you leave any physical wiring to a qualified electrician - this wiring guide is intended purely as a tool to help with the process of choosing the correct unit for your needs.
