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Leak Detection / Design Guide

Design Guide -

AquiTron Refrigerant Gas DetectionWhether you are designing a refrigerant gas (air conditioning gas) leak

detection system for a hotel, an apartment building, office space, concerthall or public building, gas leaks and emissions are a concern. You have

to ensure that your systems are safe, that adequate monitoring is in place,that you are complying with regulations and still keep costs under control.

There are many different worldwide standards, however the main reasonfor detection of gas is to, protect personnel, protect the environment and

save costs.For reference the standards in the UK and parts of Europe are - F-Gasregulations, BS EN378 and BREEAM.

Exposure LimitsRefrigerant gas manufacturers supply a MSDS and COSHH data sheet,

these typically state 1000ppm for an 8 hour period, this is a time weightedaverage (TWA).

When do I Need Refrigerant Detection?There are guidelines on the maximum volume of refrigerant that couldbe discharged into a space without the need for a fixed refrigerant sensor,

also known as practical limits. These two examples have been taken

from BS EN378 part 1 and have been widely used for air conditioningapplication for hotel bedrooms and small office spaces. The values are0.44kg/m for R410A, 0.33kg/m for R407c. Above these values a sensoris required. Other international standards use similar values as a guide.

How Many Sensors do I Need?In many applications such as small offices and hotel rooms, one sensor

mounted at low level will provide the desired level of protection. This doesdepend on the size of the room and the quantity of air conditioning units.

There are no published regulations or standards to help with this.There have been various good practices and good rule of thumb which

engineers have used in the past. These are:

one sensor for every 50m of floor area & the second

one sensor for each air conditioning unit within the space.

These guides typically do not apply to chiller and plant rooms.

Where Should Sensors be Placed?The ability of a system to detect/measure the refrigerant is dependent on

the location of the sensor. The sensor may be remotely located up to 100metres from the controller. The controller and sensor should be firmlymounted indoors. The controller should be located in an area where thedisplay is easily seen.

The sensor location should be approximately 200 300mm above thefloor in an area where refrigerant vapours are most likely to accumulate.

Sensors should be located in low-lying areas for occupant safety or neareach potential leak source for if refrigerant conservation is a high priority,

such as, ceiling voids.Systems used to protect personnel shall have their sensors located in

such positions that they monitor the concentration at heights of theoccupants, taking into account the characteristics of the refrigerant used

e.g. at less than bed height with heavier than air gases in an hotel room.EN378 states that a ceiling void is regarded as part of the human occupied

space unless it is airtight, therefore monitoring in ceiling voids would notbe acceptable. Systems shall operate a supervised and/or audible alarmso that appropriate action may be taken by the occupants or initiated bytrained personnel and/or shall close the fractured refrigerant line by

suitable valves to limit the rise in concentration within the human occupiedspace.In chiller rooms and plant rooms these sensing points should beconsidered.

Low level close to the chiller

Pressure vent line (monitoring leak from the safety valve)

Extract duct

For further information contact our technical department

Aquilar Ltd

Weights & Measures House20 Barttelot Road Horsham

West SussexRH12 1DQ

Tel : 01403 216 100

Fax : 08707 940 320

Email : ajmn@aquilar.co.uk

Website : www.aquilar.co.uk

Design Guide -

TraceTek & AquiTron Leak DetectionTraceTek leak detection systems can be utilised in a variety of

installations to detect water, chemical or fuel leaks. TraceTek sensorcables detect and locate leaks along their entire length. TraceTek point

sensors detect leaks at a specific point. Virtually any number of pointsensors can be combined with sensor cable on a leak detection single

circuit.The following information is provided for initial guidance only. Complete

product information, including selection guides, data sheets, installationinstructions and operating manuals can be downloaded from our website.

Sensor SelectionThe first design task is to select the most appropriate sensor type basedon the liquid to be detected and the area to be monitored.

Water DetectionAT-PROBE should be selected for areas requiring only a single point of

detection, such as lift pits, drip trays under HVAC units and plant rooms.TT1000 sensor cable should be selected for areas in commercial building

applications where larger area coverage is required, such as under raisedfloors in computer or telecom rooms, in building service/utility areas, etc.

TT1100-OHP sensing cable has been specially designed for suspended

piping applications were the cable is attached to the bottom of the pipe.Fuel Oil DetectionTT5000 sensor cable should be selected for fuel and oil detection.

AT-OPSEN, optical sensor probe should be selected for areas requiringonly a single point of detection, such as lift pits, below tanks andgenerators.

Sensor LayoutThe next design task is to determine the optimum sensor layout. The

sensing cable or point probe should be positioned so that leakage fromthe potential leak sources will contact the sensor quickly, before reaching

any critical equipment, cables or other items to be protected.

Alarm Module SelectionDepending on the size of the leak detection system and accessibility of

the sensors, an appropriate alarm (or alarm and locating) module must

be selected.Small Area Circuits for small leak detection circuits (normally thoseless than 40 meters of sensor cable in a single area), a simple alarmmodule may be selected. The AT-LDM and AT-SZA modules providelocal indication of the system operating status via LEDs, plus voltage-free

contacts for remote connection to external alarm signals, remoteannunciation panels, or building management systems.Large Circuits, Concealed Sensors, or Separated Areas for largecircuits (normally more than 40 meters or where sensors are distributed

between several separate areas) or installations where the sensor isconcealed and normally inaccessible, an alarm and location module is

most appropriate. The digital TTDM-128 panel provides voltage-freealarm contacts, 4-20 mA output, and digital communication via simple

RS-485 wiring and the ModBus protocol.Alternatively, TTSIM modules can be connected either to the TTDM-128

or directly to a building management system via RS-485 wiring. TheTTSIM supports ModBus and Johnson Controls Metasys protocols

directly, providing complete sensor status and leak location informationdigitally to the host system. The TTDM-128 can be connected to as many

as 128 TTSIMs via a single RS-485 network, allowing extremely largeleak detection systems to be easily configured and integrated.