SuperlecDirect - ElectriciansForums.net Electrical Suppliers
This official sponsor may provide discounts for members

Discuss Fluorescent tube light help in the Electrical Forum area at ElectriciansForums.net

D

Delboy247

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:  American Electrical Advice Forum

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??
 
Instyle LED Lighting Specialists UK
This official sponsor may provide discounts for members

Strima

-
Arms
Esteemed
C type should be OK but you need to check your Zs is suitable for the MCB.

What do the manufacturers recommend?
 
E

egginyourface

  • Thread Starter Thread Starter
  • #3
multiply 7.25 amps by 1.5.
 

Jimmy Boy

-
Arms
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
 
E

egginyourface

  • Thread Starter Thread Starter
  • #6
Test your zs at the last light. maximum zs for 10 amp ctype is 1.84 ohms
 

Jimmy Boy

-
Arms
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
 
E

egginyourface

  • Thread Starter Thread Starter
  • #10
but to determine your highest reding u need to find the last point
 

plugsandsparks

-
Arms
Esteemed
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.
 
D

Delboy247

  • Thread Starter Thread Starter
  • #15
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.
 
D

Delboy247

  • Thread Starter Thread Starter
  • #16
Is there a formula for flourescent lighting??
 
E

egginyourface

  • Thread Starter Thread Starter
  • #17
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
 

plugsandsparks

-
Arms
Esteemed
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.
 

plugsandsparks

-
Arms
Esteemed
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
 
D

Delboy247

  • Thread Starter Thread Starter
  • #24
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.
 

Jimmy Boy

-
Arms
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
 
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
 
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.
 
P

Plonker 3

  • Thread Starter Thread Starter
  • #30
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.
 

plugsandsparks

-
Arms
Esteemed
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,
 
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

-
Arms
Esteemed
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.
 
S

steveberry11

  • Thread Starter Thread Starter
  • #37
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

-
Arms
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)
 
S

steveberry11

  • Thread Starter Thread Starter
  • #39
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.
 
S

steveberry11

  • Thread Starter Thread Starter
  • #40
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

-
Arms
Esteemed
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
 
S

steveberry11

  • Thread Starter Thread Starter
  • #42
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.
 

Reply to Fluorescent tube light help in the Electrical Forum area at ElectriciansForums.net

Top Bottom