OP
amberleaf
3% of 230v = 6.9v
5% of 230v = 11.5v
5 x 230 ÷ 100 = 11.5v
● Tables 41.2 , 41.3 , 41.4 , Zs if the Measured Zs value exceeds 80% of the given values , a more precise measurement may have to be made to satisfy the Requirements BS-7671, p - 361
Uo 230
Zs ( m ) ≤ 0.8 x ------ Ze Zs
Ia 24A = 9.59Ω ( 0.8 x 9.59 = 7.6
The Maximum circuit length is then the smallest of 2 to 4 Regs , 4D5 18mV assuming Ib 32A
Lvd = 4 x 11.5 x 1000 ÷ 32 ÷ 18 ÷ 79.9m
Lvd = 2 x 11.5 x 1000 / 20A / 18mV = 63.8m Lvd = 4 x 11.5 x 1000 / 20A / 18mV = 127.7m
The following values are for T&E cable p282 1.0mm = 44 (mV/A/m)
1.5mm = 29 ( mV/A/m )
2.5mm = 18 ( mV/A/m )
433.2.1 ( Ib ) in each leg of cable is not to exceed ( 20A ) current will not be the same all round Ring , ← ← Assumed to be 20A at far end Additional – 12A evenly Distributed , ( 32A + 20A + 52A ÷ 2 = 26A
Lvd = 4 x 11.5 x 1000 ÷ 26A ÷ 18mV = 98.3m 433.1.5 , ring final circuit , 2.5mm2 & 1.5mm2 ( cable double , cable length to farthest point ) some home work ,
● BS-7671 does not give maximum Zs values for BS 3871 mcb's. ● if the maximum Zs value for a circuit in a TN system cannot be met, the circuit may be protected by a 30mA RCD . 531.3.1 : ● If the maximum Ze value for a TN system cannot be met, the installation may be protected by a 100mA RCD and treated as a TT systems 531.3.1 , 411.5.1 , 411.5.2 , 411.5.3 :
Maximum Ze values for TN-S & TN-C-S systems Typical maximum values published by Public Electricity Suppliers are ↔TN-S : 0.80 ohms ↔ TN-C-S : 0.35 ohms
● Ze Test Sequence ● Turn off the supply to the ccu , ● Disconnect the main earthing conductor from the main earthing terminal , ● Using an earth fault loop impedance tester connect the earth lead to the main earthing conductor, the phase lead to the phase conductor of the incoming supply and the neutral lead to the neutral of the incoming supply and perform a test , ● Reconnect the main earthing conductor , ● Re-instate the supply , ● Zs Test Procedure , ● The Zs value must be measured at the furthest point on each circuit , ● Direct measurement of Zs can only be made on a live installation. The main earth and bonding earth and conductors are not disconnected. At the furthest point on the circuit from the ccu perform an earth fault loop impedance test. The reading given by the loop impedance tester will usually be less than Ze + ( R1+R2 ) because of parallel earth return paths provided by any bonded extraneous conductive parts ,
IT ,
This is for the Cowboy ← that put Singles Cables Plastered in the Wall tapped off a Spur on Ring
For Computers , I feel public is just not aware of the difference of a professional Electrician and a Cowboy still Money ,
Ps , he left his horse tied up in the garden , where’s John Wane
Mr Cowboys if you can READ this , you can put other people at Danger ,
543.7
● Earthing requirements’ for the Installation of equipment having High Protective Conductor currents ,
● Leakage current is approx 2-3 mA Per Computer , if to many computers are installed on One Ring “
Or Radial “ circuit – Protected by RCD , then the RCD may disconnect due to the Aggravate of the
Leakage currents Exceeding the rating of the Ring of the RCD ,
If this is the case – Less Computers on each circuit should be considered
● Clean Supplies ,
Computer supplies to Computer and other IT equipment must be “ Clean “ and Secure ,
● Clean Supplies can be provided by installing Ring or Radial circuit from as close to
The Main intake of the CCU as possible ,
● If you are using a SWA at all use 3 – core
● A clean Earth will be a Copper-core of an Armoured cable rather than using Armour itself ,
Copper cable has a Lower Resistance than Steel of the size ,
● An alternative to this is the use of “ Special Mains Filters “ for IT circuits ,
● Clean Supply – not subject to “ Interference “ on the mains supply secure , -
Not likely to “ Trip Out , unexpectedly or be turned off by Accident ,
● run a 10.0mm2 single with your 2.5mm2 Use a bigger Earth on Domestic ,
IT , 16A , 2.5mm2 – 10.0mm2 earth
Most people are turning one room to there Office ,
543.7.1.3 Equipment having a protective conductor current exceeding 10mA ,
If you have 10mA , you do Not Spur off a Ring if more that 10mA
5% of 230v = 11.5v
5 x 230 ÷ 100 = 11.5v
● Tables 41.2 , 41.3 , 41.4 , Zs if the Measured Zs value exceeds 80% of the given values , a more precise measurement may have to be made to satisfy the Requirements BS-7671, p - 361
Uo 230
Zs ( m ) ≤ 0.8 x ------ Ze Zs
Ia 24A = 9.59Ω ( 0.8 x 9.59 = 7.6
The Maximum circuit length is then the smallest of 2 to 4 Regs , 4D5 18mV assuming Ib 32A
Lvd = 4 x 11.5 x 1000 ÷ 32 ÷ 18 ÷ 79.9m
Lvd = 2 x 11.5 x 1000 / 20A / 18mV = 63.8m Lvd = 4 x 11.5 x 1000 / 20A / 18mV = 127.7m
The following values are for T&E cable p282 1.0mm = 44 (mV/A/m)
1.5mm = 29 ( mV/A/m )
2.5mm = 18 ( mV/A/m )
433.2.1 ( Ib ) in each leg of cable is not to exceed ( 20A ) current will not be the same all round Ring , ← ← Assumed to be 20A at far end Additional – 12A evenly Distributed , ( 32A + 20A + 52A ÷ 2 = 26A
Lvd = 4 x 11.5 x 1000 ÷ 26A ÷ 18mV = 98.3m 433.1.5 , ring final circuit , 2.5mm2 & 1.5mm2 ( cable double , cable length to farthest point ) some home work ,
● BS-7671 does not give maximum Zs values for BS 3871 mcb's. ● if the maximum Zs value for a circuit in a TN system cannot be met, the circuit may be protected by a 30mA RCD . 531.3.1 : ● If the maximum Ze value for a TN system cannot be met, the installation may be protected by a 100mA RCD and treated as a TT systems 531.3.1 , 411.5.1 , 411.5.2 , 411.5.3 :
Maximum Ze values for TN-S & TN-C-S systems Typical maximum values published by Public Electricity Suppliers are ↔TN-S : 0.80 ohms ↔ TN-C-S : 0.35 ohms
● Ze Test Sequence ● Turn off the supply to the ccu , ● Disconnect the main earthing conductor from the main earthing terminal , ● Using an earth fault loop impedance tester connect the earth lead to the main earthing conductor, the phase lead to the phase conductor of the incoming supply and the neutral lead to the neutral of the incoming supply and perform a test , ● Reconnect the main earthing conductor , ● Re-instate the supply , ● Zs Test Procedure , ● The Zs value must be measured at the furthest point on each circuit , ● Direct measurement of Zs can only be made on a live installation. The main earth and bonding earth and conductors are not disconnected. At the furthest point on the circuit from the ccu perform an earth fault loop impedance test. The reading given by the loop impedance tester will usually be less than Ze + ( R1+R2 ) because of parallel earth return paths provided by any bonded extraneous conductive parts ,
IT ,
This is for the Cowboy ← that put Singles Cables Plastered in the Wall tapped off a Spur on Ring
For Computers , I feel public is just not aware of the difference of a professional Electrician and a Cowboy still Money ,
Ps , he left his horse tied up in the garden , where’s John Wane
Mr Cowboys if you can READ this , you can put other people at Danger ,
543.7
● Earthing requirements’ for the Installation of equipment having High Protective Conductor currents ,
● Leakage current is approx 2-3 mA Per Computer , if to many computers are installed on One Ring “
Or Radial “ circuit – Protected by RCD , then the RCD may disconnect due to the Aggravate of the
Leakage currents Exceeding the rating of the Ring of the RCD ,
If this is the case – Less Computers on each circuit should be considered
● Clean Supplies ,
Computer supplies to Computer and other IT equipment must be “ Clean “ and Secure ,
● Clean Supplies can be provided by installing Ring or Radial circuit from as close to
The Main intake of the CCU as possible ,
● If you are using a SWA at all use 3 – core
● A clean Earth will be a Copper-core of an Armoured cable rather than using Armour itself ,
Copper cable has a Lower Resistance than Steel of the size ,
● An alternative to this is the use of “ Special Mains Filters “ for IT circuits ,
● Clean Supply – not subject to “ Interference “ on the mains supply secure , -
Not likely to “ Trip Out , unexpectedly or be turned off by Accident ,
● run a 10.0mm2 single with your 2.5mm2 Use a bigger Earth on Domestic ,
IT , 16A , 2.5mm2 – 10.0mm2 earth
Most people are turning one room to there Office ,
543.7.1.3 Equipment having a protective conductor current exceeding 10mA ,
If you have 10mA , you do Not Spur off a Ring if more that 10mA
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