Questions? Feedback? powered by Olark live chat software

How Belden Fire Alarm Cable Equivalents Manage Adverse Conditions

3rd Aug 2021

Belden, an American company that has produced a variety of network and instrumentation cable for well over a hundred years, enjoys widespread acclaim and repute. For most of its history, it’s been seen as the undisputed standard of network, monitoring, instrumentation and alarm cable. It enjoys high regard across the country (and probably across the globe) reaching the point that the name Belden itself has been in some ways adopted as a “brand” to refer to general purpose instrumentation cable, as in the term, “Belden cable.”

Belden has been a contender in the industry for network and instrumentation cables since its inception in 1902, since which point it proliferated into complete signal transmissions solutions provider, selling the highest quality in networking and cable connectivity products. Innovations like its “Beldenamel” flexible-enamel insulation and the strict quality control of its products only improved its overall image as a company.

This quality is evinced as elsewhere in the durability and reliability of Belden fire alarm cable and equivalents. It’s not the brand itself that engenders quality, though. It is the commitment to understanding the conditions faced by electrical cables that requires it.

For example, marine battery cables come up against harsh conditions such as chemical corrosives and sea water. Welding cable must remain reliable in a wide range of adverse conditions including extreme weather and temperatures and even chemical agents as well. It must, nonetheless, remain very flexible and amenable, which, as you might imagine, requires a delicate balance.

Fire alarm cables, which are much more physically slight than most marine battery and welding cables, do not experience the same harsh conditions as these former examples - but they do experience a wide range of factors that can impact their performance nonetheless.

Remaining operable and reliable, even in the face of potentially dangerous environmental conditions, is a matter of the utmost importance to public safety. Fire alarm cables that do not do as much pose a direct risk to life and limb, and moreover, are unsuitable for even basic installation.

Belden fire alarm cables, and equivalents, help to stave off these concerns through their high-quality insulation and components. Here are a few of them - taking a high level view, that is - and how these fire alarm cables keep going strong.

The Difference between Riser and Plenum Space

One of the first things that electrical professionals will need to account for when they’re planning out a network system and the cables that they will use is what portion of the cables will run through plenum space and what portion will run through riser space. Cables are rated according to suitability in either circumstance and should not be used in areas for which they are not rated as appropriate.

Luckily, the differences are remarkably easy to understand. Riser space is the space that exists in the vertical shafts that run between the floors of a building, and is used for the passage of electrical conduits that supply power and allow for the exchange of information, as well as water pipes and HVAC ductwork.

Because riser space lies behind or in between the walls, conditions therein can be harsh, unregulated and unmitigated. This is a trait that it shares in common with plenum space which we are about to explore shortly. Riser space can get remarkably hot in the summer, very cold in the winter, and may potentially experience extremes of humidity throughout the seasons. For these reasons and others, there are special cables that are rated for use in riser space.

Plenum space, on the other hand and generally speaking, is the space that exists above the tiles in a drop ceiling. This is the space that is expressly reserved for conduits, ductwork and other infrastructure associated with HVAC systems, although it is not entirely reserved for them.

Plenum space may also be built into a setting to help manage HVAC costs in addition to allowing for room for the infrastructure itself. For example, in the winter, the drop ceiling can help to trap heat in the room below, rather than allowing all the warm air to rise to the ceiling, leaving the room cold.

In the summer, the opposite occurs; there is less volume of air for the HVAC system to keep cool, and hot air accumulates in the plenum space. Since the HVAC system does not serve the plenum space, this is one of the issues associated with running electrical cables and wires through the space above a drop ceiling.

Interestingly enough, and strictly speaking, plenum space does not only exist above a drop ceiling. It can also theoretically exist in the space that lies beneath a raised floor, which is also typically reserved for running ductwork and other infrastructure. Like the space above a drop ceiling, plenum space under a floor is not climate controlled, which can lead to issues when running electrical wiring under it.

It is, however, in the space above a drop ceiling that the need for special plenum rated cable becomes the most pronounced. Because these areas can get exceptionally hot in the summer, the cables installed there need to be highly heat resistant in order to function as intended.

Interestingly, the need for heat resistance in fire alarm cables extends beyond seasonal variations in temperature for reasons that should be more than abundantly clear. Namely, because fire alarm cables - including Belden fire alarm cables and equivalents - must remain operational in the event of a fire. It’s one thing if a set of marine electrical cables overheats and loses efficiency when flames are applied to it, and quite another if a fire alarm cable fails in the presence of heat.

On That Note, the Importance of Heat Resistance

Riser space can get remarkably hot, and plenum space may potentially get even hotter, making it necessary to use only riser rated or plenum rated cables for their respective situations. This is a feature you will see prominently listed among the attributes of instrumentation and alarm cables, often given as CMR (for riser rated cables) and CMP (for plenum rated cables). It is imperative that you only use cables appropriately rated for the space in which they are intended to be installed.

On the note of heat resistance, especially with respect to plenum space, there is an even more pronounced reason that fire alarm cables should be resistant. A fire alarm cable’s central role in a fire alarm network or system is to convey vital information along the nodes of said network. If it fails to do so, the system jeopardizes public health and safety.

Fire alarm cables, like other instrumentation and monitoring cables, are typically fairly light and then, and have a small gauge. This is because they typically only deal with low voltage ratings and are used predominantly for the exchange of information and not for providing power to appliances, in the same way that other building wire is. This, along with the fact that they are expressly used to power and monitor fire alarm systems, makes them potentially susceptible to heat related damage. At the very least, by the basic nature of their operation, fire alarm cables should be able to withstand the high heat associated with fire.

As a result, fire alarm cables are almost always outfitted with high-heat resistant insulation that makes them better able to withstand the rigors of fire and remain operable when they are needed most. Many of the best options in heat resistant cable may be plenum rated, but it is an important feature to look for in fire alarm cables nonetheless.

Taking It a Step Beyond Heat Resistance

In addition to the fact that fire alarm cables must have a high resistance to heat on the grounds that they should remain operable in the event of a fire, there is another, equally important reason that they should be so resistant. Actually, it has to do with the chemical composition of the insulation with which the cables are outfitted.

When you subject a polymer to heat, at a certain point, it is liable to burn. Many synthetic polymers, when they burn, produce undesirable, even overtly toxic or environmentally harmful compounds. This is the case for some electrical insulators as well, and in some instances it is unavoidable. However, in certain situations it is a reasonable risk, since most wires and cables should never be exposed to fire in the first place.

Then there are fire alarm cables, which are overtly exposed to the risk of fire as a matter of course and designation. The thing is, an open flame isn’t always required to break down synthetic insulation and result in the release of harmful byproducts. In some instances, only heating them up past a certain point will result in the release of toxic fumes and smoke.

Therefore, many fire alarm cables are rated not only according to heat resistance, but also to the type of smoke and fumes they release when they are subjected to excessive heat. For this reason it is critical that fire alarm cables are rated accordingly to ensure that they produce either no toxic fumes when they burn or a minimum.

Because the risk of fire is a realistic threat for fire alarm systems due to the very nature of their purpose, many fire alarm cables are produced with an insulation that both protects them from heat and produces very little toxic smoke and fumes when it is burned. The basic purpose is to protect building occupants and responders from exposure to damaging toxic gases and compounds; you can consult the product specifics for more information.

Dealing with Electromagnetic Interference

In addition to remaining operabel through high temperatures and being insulated with a suitable material that will produce a minimum of harmful emissions when burned, fire alarm cables, like other instrumentation cable, must deal with conditions known as electromagnetic interference, or EMI, which is also known as Radio Frequency Interference, or RFI.

Electromagnetic interference abounds in the earth’s atmosphere and arises from a wide range of causes, both natural and artificial. Electromagnetic interference, or EMI, can be disastrous for cables that carry sensitive information or control electronic devices remotely, scrambling or jamming the signal, even resulting in total data loss or complete incapacitation of the system.

As stated, EMI can arise from many natural causes, such as electrical storms, solar radiation and even cosmic noise. Many powerful sources of EMI, however, are artificial, such as cellular networks, ignition systems and radio transmitters, although all electronic devices are capable of emitting EMI in some capacity or other.

Since the nature of the data carried by alarm systems is sensitive and accuracy is vital, these systems are more susceptible to interference than other electronic systems. The greater and more complex the system is, and the greater its proximity to other electrical infrastructure, the higher the risk of electromagnetic interference adversely impacting the system.

Therefore, while it is not always absolutely necessary to protect a fire alarm system against electromagnetic interference, no harm can come of doing so. It’s also not difficult to do; many cables are what are known as “shielded” cables, which contain a metallic wrapping underneath the insulation.

This metallic insulating material creates a little Faraday Cage around the conductors of the cable, preventing EMI from scrambling or disrupting the flow of information. As a general rule, it’s advisable to protect alarm systems with as many redundancies as possible, and shielding is only one of them, but an important one nonetheless.

Resistance to high heat, insulation that does not produce toxic fumes or smoke when burned, protection against EMI, and special ratings based on intended application are just a few of the more important ways in which fire alarm cables can be manufactured to manage adverse conditions. If you’d like to learn more about the different types of fire alarm cables we sell in our online store, please get in touch with us directly. We’d be more than happy to field your questions by phone at 800-262-1598 or email at sales@ewcswire.com