With 2023 going down as the hottest year on record, experts warn that we are getting ‘dangerously close to a global warming limit’. Take this, coupled with an increase in volcanic activity, wildfires and overheating solar panels, and it’s never been more important to understand how to detect fires as early as possible – especially in ambient climates, where false alarms are so prevalent.
In our earlier article, we discussed what linear heat detection is, and what problems it solves… but now we are getting more granular. We want to break it down into ‘fixed temperature’ and ‘programmable’ or ‘dynamic’ linear heat detection types – and the applications they benefit when compared to alternative technology.
And we are starting with programmable temperature sensing – or ‘analogue’ – linear heat detection (LHD).
So, buckle in, we’ll try not to make it too technical!
Doesn’t Analogue mean ‘Old’?
No, dear reader, it doesn’t. But we understand the question!
For those of us who are new to LHD technology, the word ‘analogue’ can sometimes conjure up negative connotations, especially when used in relation to ‘digital’. We are keen to dispel the myth that analogue means old, archaic or slow – because in the fire detection market, it simply refers to the type of ‘information’ that is transmitted through a cable.
As we mentioned in our previous article, the main difference between digital and analogue, is that while both systems are triggered by heat, analogue uses the resistance change of a polymer (plastic) to activate the alarm, and digital uses the physical melting of the polymer to activate the alarm. Typically, the resistance of the polymer decreases as the temperature increases. This is known as having a negative temperature coefficient (NTC) [of resistance].
An analogue signal characterises a real number within a continuous range of values. This contrasts with a digital signal, which is a signal that represents data as a sequence of discrete values; at any given time, it can only take on, at most, one of a finite number of values. (Source: Digital Signal)
So, to make things less confusing, we are referring to the commonly named ‘analogue’ technology as ‘programmable temperature sensing’.
So, What Exactly is Programmable Temperature Sensing LHD?
Recap: Often referred to as line type heat detection, LHD is a cable-based type of early fire detection, designed to generate either an alarm, or automatically activate a fire suppression system.
The cable itself acts as a heat detector, so when a physical or electronic change occurs, this is identified anywhere along the cable’s entire length. Once the temperature around the cable reaches a certain threshold, the cable can trigger an alarm and subsequently a suppression system.
Programmable linear heat detection systems comprise a control or interface unit, a zone of a four core analogue linear heat detection cable and an end of line unit, recommended for use up to 500m.
Commonly referred to as ‘resettable LHD’, due to its ability to self-restore following a fire, the system identifies fires or overheat conditions by continuously measuring changes in electrical resistance along the detection cable. An alarm is triggered once the resistance along the cable falls below a set threshold, which is determined by the desired alarm temperature (chosen by the user).
…Hence, programmable temperature sensing.
In a nutshell, it:
- Has infinite states, the output is a function of the temperature along the whole sensor cable, continuously changing with temperature over time
- Is resettable. It returns to its original state after heating up and can be used over and over
- Is designed to provide a much needed early warning detection of fire and/or overheating
Applications of Programmable Temperature Sensing LHD systems
Coated in different materials to suit specific applications, our LHD cables are suitable for use in the majority of dirty, dusty, damp and hard to maintain environments. This is because they are unaffected by airflow, dangerous chemicals or toxins, removing the risk of reactive failure and false alarms – potentially leading to huge cost savings.
Appropriate for use in sectors such as energy, oil and gas, infrastructure and industrial, analogue works particularly well in the following applications:
With one cable benefitting from many alarm temperature – along with a pre alarm setting – and no need to replace after alarming, programmable LHD is a multi-faceted solution that is suitable for use almost anywhere. In fact, unless you need a higher ambient temperature range, or alarm point locating, we would always recommend using our ProReact Programmable.
ProReact Programmable Temperature Sensing – Thermocable’s Premium LHD Product
Thermocable launched the ProReact Programmable Temperature Sensing product range in January 2021. This innovative product is the first resettable linear heat detector (LHD) approved to EN54-22:2015 on the market. Benefitting from multiple coatings to suit any environment – including dirty, dusty, damp and humid conditions – this is the only type of integrating linear heat detector that has automatic ambient temperature adjustments.
Not only does this drastically reduce the risk of false alarms, it provides cost and time efficiencies during installation.
It is additionally equipped with a rate-of-rise activation alarm trigger that allows for a quicker response to escalations in temperature around the sensor cable. Other features include:
- VdS approved/UL listed heat-automatic fire detector
- Low installation costs/minimal maintenance effort versus alternative technologies
- Up to 500 metres of LHD cable per zone
- Three sensor cable types for multiple environments
- Modbus RS-485 output of real-time temperature data
Thermocable’s approved system has numerous alarm temperatures, all of which can be programmed on the control unit’s LCD display – or through a laptop connection. Installers also have the option to select pre-alarm temperatures to receive an early notification of an unexpected rise in temperature before a chosen alarm threshold is reached.
“The ProReact Programmable Temperature Sensing product is a detector with a simple and clear design...It benefits from good resistance to low temperatures and demanding environmental conditions, which make it very useful in protecting heavily dirty rooms, abattoirs, parking lots and hard-to-reach places, e.g. above suspended ceilings.
We have applications using this detector in numerous freezers at temperatures below -25'C, as well as in recycling plants where these detectors protect areas exposed to heavy dirt, high air humidity and mechanical damage. Therefore, the possibility of using a stainless steel-sheathed cable makes this detector resistant to mechanical damage.
We have a project awaiting implementation where the detector will protect devices that grind material for cement production. Here, too, the armored cable is irreplaceable.”
- Tadeusz Markiewicz, Quality 07
The Innovation Behind Thermocable’s ProReact Programmable LHD
We’ve been excited to get to this part – Thermocable’s Fixed Temperature LHD system is the only technology of its kind that is designed specifically to prevent false alarms in ambient conditions.
This means the system is unaffected by short circuits, weather conditions, and will only alarm when there’s a fire.
We know that sounds like an obvious one, but alternative analogue technology occasionally triggers when the surrounding temperature becomes hotter than ‘normal’, or hotter than the threshold that has been set. This creates a false alarm, which is time consuming, confusing, and in some geographies can be extremely expensive.
Historically, the most common method to mitigate for fluctuating ambient temperatures was to set a higher temperature alarm level, however this reduces the overall sensitivity of the system and therefore shouldn’t be considered “early fire detection”. Our 4-core, programmable cable, actively monitors the average ambient temperature along the cable in real time and dynamically adjusts the alarm threshold. This mitigates false activations from high(and varying) ambient temperatures but maintains a high level of sensitivity for the whole system for the detection of a hotspot, anywhere along the cable.
We can’t help but put a humble brag in here now. We are yet to discover any other manufacturer who has designed out the issue of false alarms in ambient conditions.
This is largely down to the brilliant and innovative minds of our Technical Director, Tom Robst, and Engineering & Compliance Director, Philip Wilkie, who have both been with Thermocable for a collective 55 years. In 2008, they decided there was an opportunity to elevate Thermocable, and become entirely unique – and following lotttts of research and development, they nailed it!
And of course, to make sure our designs were recognised, we also went out and got UL, VDS, EN and CNBOP accreditation..!
Why is LHD Better Than Alternative Technologies?
In addition to the above, cable based LHD performs better than any other form of early detection technology within its specified applications – with perhaps the exception of fibre optic LHD, which is on a par. However, for areas where less cable is needed, LHD is a fraction of the price for the same level of results.
Other ‘visible’ areas of fire/smoke detection need regular maintenance to ensure they aren’t impacted by dust, debris, or general wear and tear. LHD is essentially a piece of ‘fit and forget’ equipment, that lies dormant until activated.
Benefits include:
- No pre-determined alarm temperature for a given length of detection cable. Users can select a desired alarm temperature from a choice on the control unit
- No need to replace the linear heat detection system following a fire or overheat (providing the cable is not exposed to a temperature above 125⁰C)
- Pre-alarm functionality gives users early indication of rising temperature
Additionally, you get:
Increased coverage
- Every part of the cable is a detector
- Continuous detection along the entire length rather than ‘spot’ detection interposed with ‘non-detection’ cable
100% accuracy in dirty, dusty & damp environments
- Excels in environments where other detectors may fail or false alarm due to detection clogging or wear and tear
Greater Flexibility
- No pre-determined alarm temperature for a length of detection cable. Instead, users can select the desired alarm temperature from a choice of available temperatures on the accompanying control unit during installation
You can find out more by clicking here.
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If you need any help or advice in determining whether linear heat detection could be an option for you, don’t hesitate to contact us for a confidential, no-commitment chat.
