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Delboy247

Hi there went a job today to supply a light box for a shop today, it has 30 fluorescent tubes inside it done the cable calc 30 x 58watts = 1740
1740/240=7.25
So I fitted a 10amp rype b mcb and it tripped so I clamped the load going out it was reading 10.8amps and on start up it was hitting 11-12 Amps.
Now I'm thinking of fitting a 10amp type c mcb will this do it
Has anyone come across this??
 
C type should be OK but you need to check your Zs is suitable for the MCB.

What do the manufacturers recommend?
 
Firstly can I ask if you are electrically competent and/or qualified to carry out this work ?, I ask because I would like to know if you have established the cable sizes and protective device characteristics required for this load.
J
 
Has this been a new install?

Well this what I am driving at ! Is someone lobbing a huge light box on the end of some random existing cable ? for all we know it might be a bit of .5 flex lol !. If the OP can give us the supply cable size 1.0 or 1.5 this will help us determine stuff.
J
 
Depending on the type of light you need to take into account the load of the ballast, if appropriate or the HF unit. Also the power factor will also conspire to increase the current above the basic calc of adding up the tubes and dividing by the voltage.

With a tube load of what you have described i would have put it on a C16 on 2.5sqmm cable, depending on cable length.
 
The box is pre wired in 1.5mm t + e, I run in a 1.5mm fp cable 10 metre run to the first connection done r1 + r2 at the furthest point all good turned it stuck a clamp metre on the load side with it reaching 10.8 amps.
 
this is what i think delboy needs to do.

Find out how many lights this circuit is supplying.
determine the cable size and length
do a r1 r2 test on the circuit. every point.
last point will be the highest
If it higher somewhere in the middle then yes u may have a loose connection
do a live test ze at the board
do a live zs test at the last point
This will give you ur zs
if its below 1.84ohms then bang a 10 amp type c

jobs a good'un
 
There are two main types: switch start and HF, their supply characteristics are different. Also i have noticed that as switched start ones get older they pull more current, so leave plenty of overhead.
 

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