The idea of a fire guard is familiar to most people, but a boiler guard is a different matter entirely. These devices are not usually seen on a boiler at all, but serve to protect elements outside of the boiler, such as the flue. Boiler guards are designed to protect certain areas of the boiler from electrical charge, and damage caused by contact between points. The most common of these types of guards is the terminal guard, which protects the outside edge of the flue.
Terminal boiler guards protect the flue from damage, particularly when it has been fitted at a low level. For example, a boiler can be fitted to be less than 3 feet above a flat roof or balcony, in order to prevent contact between it and the terminals. Most terminal guards are plated with contact resistant metal such as zinc in order to better protect the flue from damage. As well as straight, cage-like terminal guards, users can also purchase small ones which are more like a cone shape, which can be fitted on smaller flues.
The guard acts as a barrier between the appliance and both the ground, or nearest low point, and other terminals which are extending from the boiler. Although terminal guards are usually fitted with zinc to protect them, they are not suitable to be used with a condensing boiler, and plastic guards have been developed for this purpose.