Fluorescent tube light help

[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??

 

[Delboy247]

Is there a formula for flourescent lighting??

 

[egginyourface]

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

 

[Plonker 3]

thats what the r1 + r2 test is for

What about if you use the R2 method?

Zs should be determined at the furthest point of each circuit, on a radial at last point, on a ring with spurs at the spurs with the highest reading.
J

I always record the highest reading.

 

[spark 68]

Is there a formula for flourescent lighting??

It was to apply a factor of 1.8 (multiplied by), for the switch gear, but I cannot see this at the moment in the BGB

 

[plugsandsparks]

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.

 

[Delboy247]

Egg mentioned 1.5

 

[Delboy247]

They hf ballasts

 

[plugsandsparks]

HFs vary alot in efficiency, manufacturers data will help but if its running 10.8 you have little choice but to go C16, 1.5 might work if the runs are not too long

 

[Delboy247]

HFs vary alot in efficiency, manufacturers data will help but if its running 10.8 you have little choice but to go C16, 1.5 might work if the runs are not too long

The run is 10 metres mate what do you think I can easily change the wiring to 2.5mm for a c16 or change the mcb to a c10.

 

[snowhead]

Is there a formula for flourescent lighting??

Yes, you've got enough information to determine it;

10.8 / 7.25 = 1.49

12 / 7.25 = 1.65

Seems to agree with earlier posts.

 

[Delboy247]

Yes, you've got enough information to determine it;

10.8 / 7.25 = 1.49

12 / 7.25 = 1.65

Seems to agree with earlier posts.

Interesting.

 

[Jimmy Boy]

What about if you use the R2 method?


I always record the highest reading.

Agreed on a ring with spurs, with a Radial how can a higher reading be anywhere except at the end unless you have a fault or an external influence ? If you have done the r1 stuff first, I fail to see how the impedance can be higher mid circuit than end circuit on a Radial ?
J

 

[somersetsparks]

HFs vary alot in efficiency, manufacturers data will help but if its running 10.8 you have little choice but to go C16, 1.5 might work if the runs are not too long

Do the fittings not have to fused to be connected to a 16a mcb? Seem to remember havinbg to install a load of fused fittings when the circuits were 2.5/16A

 

[Guitarist]

You say it is pre-wired? Did it come with any literature/manufacturers instructions? If so, these would probably tell you what overcurrent device you need to fit, and you can install the supply accordingly.

 

[Plonker 3]

Just a personal preference, but checking every point ensures all current using points meet the required Zs rather than relying on a installation being perfect because one other test says all is good.