Length of Cable in Lighting Circuit?
- Thread starter dizz
- Start date
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err, if this is from a diagram, use the scale and measure your intended route. allow 2.5 metres for vertical drops and add 10% fudge factor.
If its an existing cable. measure the R1+R2 value and use the table in the OSG to get the length.
Simples!
If its an existing cable. measure the R1+R2 value and use the table in the OSG to get the length.
If its an existing cable. measure the R1+R2 value and use the table in the OSG to get the length.
Simples!
Surely using the R1 + R2 value to imply the length might mean that you get a longer length if you've got a dodgy connection. I thought it might be the other way round, even in an existing circuit. i.e. estimate the length, then calculate the R1 + R2 to check it is within the tabulated limits? If so, how would I deal with the switches?
Dodgy connections - I do not understand. That phrase is not in my Theasuarus.
R1+R2 is not a tabulated value. It is Zs that is tabulated. You need to check that to confirm that the CPD will trip in the required time.
Can we take a step back. Can you explain what you want to achieve by making these measurements?
In my experience I have never found a lighting circuit in a normal sized house that exceeds the EFLI measurements as a result of too long a cable run. - Even with 1.0mm². Vd may be an issue, but its also unlikely.
R1+R2 is not a tabulated value. It is Zs that is tabulated. You need to check that to confirm that the CPD will trip in the required time.
Can we take a step back. Can you explain what you want to achieve by making these measurements?
In my experience I have never found a lighting circuit in a normal sized house that exceeds the EFLI measurements as a result of too long a cable run. - Even with 1.0mm². Vd may be an issue, but its also unlikely.
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Ok Step Back - I wanted to do a quick check on a circuit to check that the resistance ties up with the length. So I wanted to estimate the length, and then do the R1 and R2 dead test, looking up the resistance per metre run in the tables to see whether the resistance reading I had taken is less than the length of cable I have estimated.
Having asked the question, there is probably no quick way to do it anyway, and if I am testing the furthest light in the circuit, I only have to worry about the phase switch length to add to the overall circuit length anyway.
Having asked the question, there is probably no quick way to do it anyway, and if I am testing the furthest light in the circuit, I only have to worry about the phase switch length to add to the overall circuit length anyway.
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