FT2GAS
Gaseous Extinguishing System
Rev No. 1.3
37
4.3
Appendix C - Cable Types and Calculations
4.3.1
General Requirement
The CIE cable type and cable installation shall follow all the application related current standards and
regulations, such as the AS/NZS 3000, AS/ACIF S-009, AS1670 and NZS4512 standards.
4.3.2
Real Cable Resistance
The maximum system cable length determined primarily from its cable cumulated resistance. The
cumulative cable resistance is the total resistance of all installed copper wire used in the related circuit
loop that includes both the forward path and the returning path.
The manufacturer’s specified cable resistance is specified in ohms per meter.
To calculate,
Real Cable Resistance = (Manufacturer’s Specified Cable Resistance Cable Resistance x 2) x overall
length
For example,
A cable length of 5m is required with a return path. Electra Cables, FC7402LD was to be used.
Electra Cables, FC7402LD from Table 20
gives 0.02Ω/m for
its Manufacturer specified cable resistance.
Hence, the overall Real Cable Resistance over 5 metres will be,
(0.02x2)x5 = 0.2Ω
Some common used cable parameters are listed in the following table.
Table 20 Cable Resistance of the Reference Cables
Cable Type
Copper Area Insulation
Manufacturer specified
cable resistance
Real cable resistance
Electra Cables, FC7502HD 1.0mm
2
250 / 250 V 0.02 Ohms / m
0.04 Ohms / m
Electra Cables, FC7502HD 1.5mm
2
250 / 250 V 0.0128 Ohms / m
0.0256 Ohms / m
Electra Cables, FC7502HD 1.5mm
2
0.6 / 1 KV
0.0128 Ohms / m
0.0256 Ohms / m
4.3.3
Zone Cable
The zone cables are required to have less than 50 Ohms of the total cumulated cable resistance. The
cable maximum length is calculated by the following equation.
L
MAX
= 50 / R
RPM
(Equation 1)
While
L
MAX
- the maximum cable length,
R
RPM
- the real resistance per metre.
