calculating diversity for lighting circuit

[swc]

Hi I'm sitting my unit 4 exam for C &G 2330 electrotechnical course.
I'm a little confused to calculate the answer to this question

I can't get the same answer

[FONT=Arial, Arial, sans-serif]10 x 60w fluorescent lamps will have an assumed current demand at 230v of[/FONT]



[FONT=Arial, Arial, sans-serif]a. 2.6A[/FONT]
[FONT=Arial, Arial, sans-serif]b. 4.35 A[/FONT]

[FONT=Arial, Arial, sans-serif]c. 4.7 A[/FONT]

[FONT=Arial, Arial, sans-serif]d. 7.83 A.

I


[/FONT]

 

[Electricalserv]

Hi I'm sitting my unit 4 exam for C &G 2330 electrotechnical course.
I'm a little confused to calculate the answer to this question

I can't get the same answer

10 x 60w fluorescent lamps will have an assumed current demand at 230v of



a. 2.6A
b. 4.35 A

c. 4.7 A

d. 7.83 A.

I

Answer is 2.6A without diversity!

 

[telectrix]

nope. the lamps are 600watts alone. I = 1.8 x 600/230 = 4.7A.

 

[mayfair]

sure m8?............ sorry I cant read properly

nope. the lamps are 600watts alone. I = 1.8 x 600/230 = 4.7A.

 

[Electricalserv]

Whys that?

 

[swc]

nope. the lamps are 600watts alone. I = 1.8 x 600/230 = 4.7A.

Hi teletrix,
where in the onsite guide did you get 1.8 from?

 

[telectrix]

that'e my thoughts. allowing for the juice consumed by the ballasts, some of it as wasted heat. the question is obviously acedemic, as 10 fluorescents would probably have sufficient leakage to take out the RCD ( if fitted )

 

[londonlec]

I make it 4.7 too.

Sorry - exam conditions!!.... 4.7A

 

[telectrix]

Hi teletrix,
where in the onsite guide did you get 1.8 from?

not from the on site guide, mate, from the soogy grey matter between my ears that i laughingly call a brain. ever tried getting hold of a ballast when it's been on a few hours? hot enough to melt T/E if some numpty has sandwiched it between the ballast and the casing. that'e the 1.8 factor.

 

[beaver74]

I would say that using 1.8 in only for start up current the question is asking for running load

 

[swc]

No. I don't think any qualified electrician is brave enough to let me install anything. My tutor was afraid to turn on the installation I had installed for my 206 exam.
As a matter of fact it switched on 1st time and didn't go bang at all. If it had done I would of blamed it on the test equipment. The insulation resistance test/ continuity of cpc were both normal.

 

[Engineer54]

10 x 60w fluorescent lamps will have an assumed current demand at 230v of[/FONT]
a. 2.6A
b. 4.35 A
c. 4.7 A
d. 7.83 A.

Your correct Tel, unless you know the actual load current of a Flu fitting, you give any calculated figure, a times factor of 1.8 as the ''assumed'' current demand....

 

[telectrix]

i can't remember if that's in the book. just something i've used for years. op was asking if it was in the osg. mine's in the van.

 

[ezzzekiel]

yup my answer also

 

[Engineer54]

Been using that 1.8 factor since my first training days... It's probably way over on the safe side these days with today's far more efficient control gear incorporated in Flu's. But not toooo many years ago, there were instances of 8' flu fittings drawing neigh on 2A a piece!!! ...lol!!

 

[davelerave]

ya the 1.8 multiplier isn't for startup

it's prob a bit dated now with modern fittings higher power factor and efficiency

 

[beaver74]

ya the 1.8 multiplier isn't for startup

it's prob a bit dated now with modern fittings higher power factor and efficiency

my mistake then

 

[davelerave]

no worries i make loads of 'em

 

[tony mc]

Its still in Appendix 1 OSG max demand & diversity but in the small print in note 2 Table 1A.