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??

 

[plugsandsparks]

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.

A C16 can run on 1.5 if you can get the right ZS readings for it. Fitting a C10 is high risk if its running 10.8 now, you could well be back after tripping in hot weather assuming it stays in long enough for you to leave the premises.
I cannot say because i dont know you total cable run through the switches and the Zdb.
What i do is (before ordering cable) measure Zdb stride the cable run for an idea of cable length then over a coffee decide how many circuits and how fat a cable to use.
You wont get a definitive answer here because your variables are unknown, but i would be surprised if you cannot make it work on a C16 and 2.5, as you have run the cables, if your ZS at the end of your run is less than 1.16ohms than fit a C16, if its greater then oops,

 

[Guitarist]

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.

Agree. Picks up any loose connections that way.

 

[spark 68]

Egg mentioned 1.5

Found it in the OSG Append. A Diversity, see note 2 on page110.

Final circuits for discharge lighting etc...etc. the demand in VA is taken as the rated lamp watts multiplied by not less than 1.8, unless more exact information is available.

 

[spark 68]

I knew it was X 1.8, just wasn't sure where it was listed.

 

[Delboy247]

I knew it was X 1.8, just wasn't sure where it was listed.

That's why these sites are good we can't all know everything it all makes sense now.

 

[plugsandsparks]

1.8 sounds about right for ballasted fittings although i have seen 2.0 times for older ones

 

[steveberry11]

The correct method for calculating the protective device is as follows.

30 x 58 x 1.8 = 3132 W

3132 Divide be 230V = 13.61A

The protective device should be 16A

The normal type this type or lighting should be type C.

Cable calculations should be based on a load of 13.61A

 

[tigerpaul]

As the others have said, check your Zs at the end of line (should be the highest) and just make sure it doesnt exceed the maximum value given for the mcb you require. (in this case a Type C)
If it does exceed that value, how about changing for an rcbo? Or reduce the earth loop impedance by adding supplementary bonding (if practical)

 

[steveberry11]

As the others have said, check your Zs at the end of line (should be the highest) and just make sure it doesnt exceed the maximum value given for the mcb you require. (in this case a Type C)
If it does exceed that value, how about changing for an rcbo? Or reduce the earth loop impedance by adding supplementary bonding (if practical)

Or carry out cable calculations and get it right first time.

 

[steveberry11]

As the others have said, check your Zs at the end of line (should be the highest) and just make sure it doesnt exceed the maximum value given for the mcb you require. (in this case a Type C)
If it does exceed that value, how about changing for an rcbo? Or reduce the earth loop impedance by adding supplementary bonding (if practical)

Why do electricians need to be reminded of this stuff time after time?

 

[plugsandsparks]

The correct method for calculating the protective device is as follows.

30 x 58 x 1.8 = 3132 W

3132 Divide be 230V = 13.61A

The protective device should be 16A

The normal type this type or lighting should be type C.

Cable calculations should be based on a load of 13.61A

Doesn't always work, mate. You can easily run out of ZS using cables rated for 13a e.g. 1.5. Its nearly always ZS i am chasing not load or volt drop when using C and D type breakers.
Worst case scenario is when the Db is at one end and the switch is at the other end

 

[steveberry11]

Doesn't always work, mate. You can easily run out of ZS using cables rated for 13a e.g. 1.5. Its nearly always ZS i am chasing not load or volt drop when using C and D type breakers.
Worst case scenario is when the Db is at one end and the switch is at the other end

If you follow this method and the correct cable calculations the Zs will be correct. It may mean you need a 2.5 or greater.
But it I'll be correct.