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Leak Detection 13 gh isolation cells Detection cuts losses
refrigerant containment has grown to become air conditioning industry.
IT IS ESTIMATED that as much as 30% of refrigerant is lost annually through leaks in refrigeration and HVAC equipment.
The environmental impact, refrigerant replacement costs and tightening legislation means that end-users now give leak detection a very high priority.
One of the latest solutions is a ‘next generation’ precision leak detection gas that not only addresses environmental concerns but provides customers with an effective solution for detecting leaks right down to less than five grams per year.
Trace-A-Gas is a 5%
With traditional technology, the whole system is shut down in the event of a leak, impacting occupants throughout a building until the source of the leak can be identified and repaired. The new approach means that only the immediate area served by the compromised circuit suffers loss of service. David Dunn, general manager, says: “This technology is a major step forward and extremely useful for applications such as hotels and multi-tenanted buildings. It means that, in the unlikely event of a leak, those areas unaffected can continue to function as normal and receive cooling and heating as required.
“The benefits are obvious, from an environmental, commercial and customer service point of view.” The approach uses a number of separate ‘isolation cells’ throughout a building, consisting of an RBC-RD3 refrigerant concentration sensor, a pair of motorised isolation valves, and an RBC- RD7 control box.
Refrigerant pipework – liquid and gas – outside each conditioned space is fitted with motorised valves, the room sensor is located within the space at low level, and the control box is mounted next to the indoor unit.
In the event of a leak, the sensor detects the presence of refrigerant in the room and triggers an alarm and a fault code on the indoor unit; this
is detected in turn by a central controller or BMS, and initiates the isolation sequence. The motorised valves close automatically, effectively isolating the conditioned space from the rest of the system. At the same time, on-site maintenance staff and service contractors are notified of the alarm status and its location, and can zero-in on the problem to resolve it.
The system is primarily designed for use with Toshiba VRF systems, but can also be used with split systems. It can be specified on new installations or retrofitted on Toshiba equipment on existing sites.
The manufacturer has developed an improved version of the RBC-RD3 in-room refrigerant concentration sensor. This unit has a recessed design to protect it from accidental damage, and can be fitted into a standard, single electrical back box.
While the standard version is supplied in white plastic, the design of the face-plate can be changed to match the room décor or client specification, particularly important for application in hotels. The device is recessed into a wall approximately 150mm from floor level within the conditioned space, and connected to the indoor unit via supplied leads. On detection of a higher- than-normal refrigerant concentration, it shuts down the indoor unit and gives an audible and visual alarm.
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hydrogen and 95% nitrogen mixture which is non- flammable and non-toxic. Hydrogen is a light element and is the smallest molecule, so it moves quickly through a system and can pass through even the smallest leak. Its low viscosity makes it easy to flush out and vent away.
Leak detection devices with high levels of sensitivity are able to detect even ‘pinhole- sized’ leaks, which are far more problematic to locate. Developed to focus on the difficult- to-find leaks, this method has been proven to be far more effective at detecting smaller leaks than traditional methods.
Trace-A-Gas was successfully used on a pilot site using a supermarket refrigeration pack.
A pinhole leak which had gone undetected by a bubble soap spray and a further four tiny leaks were highlighted including one on a joint covered by Armaflex. None of these had shown up during an overnight pressure decay test at 27.5 bar. The trials also confirmed that this method was up to 100 times more sensitive than soapy bubble spray and when used with a suitable electronic hydrogen detector, offers a valuable tool to eradicate leaks.
All leak detectors require a level of skill in using them and their effectiveness and ease of use are important considerations by service engineers when selecting a leak detection system. Consideration should be given to the size of plant and accessibility is of equal importance.
A good leak detection kit will offer the ability to test all areas of the system, including insulated or difficult to access pipework where a spray device cannot easily be used, and real time results, which ensures less time is spent on site
If unchecked, leaks can have a detrimental effect on plant while compromising company’s legal obligations. They can impact health and safety requirements, increase running costs as well as servicing costs and have a detrimental impact on the environment.
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