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lukese

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hi people a few of you may remember my thread a few months ago about giving up my apprentiship and finding another way of qualifying as the training company that is doing my appprentiship are to be honest quite shocking! (JTL)

anyway long story short, im back on speaking terms with JTL haha got a new training officer that i have seen more in the last two months than the one before in 2 years! i only have my log book to do and this in all complete barring one question that he hit me with the other day, its got to be back with him by the 15th but im away on monday so need to post it this weekend and i have left my Reg book and on site guide in the site box a work.

my question is as follows and any answers would be greatfuly recieved as this is gonna get me my gold card finally after 5 years of messing about haha ;-)



basicly i wired a fire alarm conventional system so one leg out the panel to an end of line, ie radial. This was wired in 2 core+ cpc 1.5 fp 200 gold. im guessing the length of the circuit was about 20 meters maximum as it was only a little gas extinguisant system (small comm's room) i took a reading of 1.9 ohms for the CPC continuity this was obtained by shorting out the cpc and live at the other end then taking a reading on a low ohm meter.

the question i have been asked is

What table did i use and what calculation did i use to make sure it was acceptable.

now if im being honest we dont normally check the regs, its only 24V running at a few mili amps, we only dig out the regs when testing our motor circuits and supplies for the panels and so forth, but if anyone could take the time and dig out a table number for me id be greatfull.


Many thanks

Luke


oh pref 16th edition as that is what was in force when the circuit was tested.




Thanks
 
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S

Shakey

  • Thread Starter Thread Starter
  • #2
well you are doing an R1+R2 check

in the OSG, think its about page 151, theres a table of R1+R2 values for different size cables, in milliohms per metre

the calculation you doing is Zs. So you are getting your R1+R2 and adding it to your Ze. you can then compare that directly with the values in the OSG (pretty sure its page 92), or take the values out of the regs, and use rule of thumb or temperature correct
 
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wayne

  • Thread Starter Thread Starter
  • #3
this seems to be a question that been asked by some one(jtl) who doesnt know the regs ;
your'e design current is in the milliamps ,your voltage is ELV ,if you were to apply current calcs ,voltage drop ,where do you start?
1.9 seems excessive for a r1+r2 value over 20metres
 
L

lukese

  • Thread Starter Thread Starter
  • #4
1.9 ohms does seem a little excessive for 20 meters but it travels through 4 bases so each base is a joint, thats prob explaines the resistance. i think i may have the on site guide in the van as a called a mate from work and he recon's all we have at work is the regs so im guessing i must still have teh on site guide somewhere.

i agree the question seems stupid to me, you look at the results and accept them, if i had got anything over a couple of ohm i would have had a problem given the lengh of the cable run, but the guys being picky and i want to qualify so gotta play there games i guess.
 
P

PAUL M

  • Thread Starter Thread Starter
  • #5
They build the hoops we jump through them,
 
W

wattsup

  • Thread Starter Thread Starter
  • #6
That is an engineers job, the designer, the manufacture of equipment. I firmly believe questions like these are not applicable to a spark installing the said circuit.

This country is going ****ing barking mad, you are not a scientist, you do not get a degree in physics even if you can solve, yet the powers that be say you should know.
All things equal, sparks iq would be 240, ministers responsible for outlandish requirements elv, 12/24v..and i'm being kind to them, i know several whom have the iq of a kit-kat.
 
L

lukese

  • Thread Starter Thread Starter
  • #7
my argument totally, we allways had this argument at college, when talking about volt drop and other such calcs, we never play no part in them the engineers decide what size cable to pull up 30 floors to a plant room, we just install it! i get the point that its handy to know how the calculation is done incase you ever went it alone but sometimes i question all the physicsc of the course.
 
W

wayne

  • Thread Starter Thread Starter
  • #8
so how do you determine (tables etc )what size cable?
 
L

lukese

  • Thread Starter Thread Starter
  • #9
one last dash at this ive been stuck in my on site guide for the last hour and this question is throwing me!

ive gone back to the original question that he asked me.


he asked me


'Confirm how you know that your continuity readings are satisfactory' for the above question stipulate values.



i replied. :- The results for the CPC where 1.9ohms it was a 1.5mm fp200 cable, i saw this as satisfactory.


he has come back with, what table did you use to check it was satisfactory and what calculation did i perform.


i cant get what he wants to know, the simply fact i got a low ohm reading tells me that i have continutity at the furtest point.


does that make it any easier for people to get what this guy was smoking when writing this question?


thanks again people.
 
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wayne

  • Thread Starter Thread Starter
  • #10
as you say you've proven continuity but i really dont think there any" tables "within the regs that you can refer to. you can try and tell him that as its elv then its not covered by the regs if he disagrees ask him to show you where it is and his qualifications
 
L

lukese

  • Thread Starter Thread Starter
  • #11
i have decieded to do exactly that after calling a few people up thinking im going mad by not knowing the answer to this question i have decided to just call the guy up first thing on monday and hope i get through to him if not ill pop it in the post with a letter explaining my problem.
 
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wayne

  • Thread Starter Thread Starter
  • #12
i think you'd need to read the entire book:eek::eek::eek::eek::eek::eek:and you'd still not find anything
 
S

Spudmiester

  • Thread Starter Thread Starter
  • #13
Perhaps its a trick question to try and catch you out. Pretty snidey if it is, tell him you rang the manufacturers tech department and they said it was ok !
 
L

lukese

  • Thread Starter Thread Starter
  • #14
i actually used table 9A on the on site guide page 158 turns out i had totally messed up the cable run after checking the drawings, it was over a year ago. the table gave resistance values of 24.20mili ohms for a 1.5mm phase and 1.5 cpc so i did the following calculation


24.20 * 80 meters / 1000

to give me a reading of 1.936 ohms

i then went on to expand my bull**** to say ' after consulting the onside guide i found this was a sufficent reading for a cable run of around 80 meters and i was happy with the reading.


What a load of Tosh.



Thanks for all your answers and input people, whos know might get my gold card yet, only been working as a spark for two years now.


oh and anyone thinking of JTL appentiship, dont bother, go college and do it off your own back, as i am now thinking of doing again, as i feel my knowledge in infieror to people i work along side of on site who did 2360 and 2330 part one and two.


Take care people



Luke
 
W

wayne

  • Thread Starter Thread Starter
  • #15
hopefully that crap will put it to bed .get your qualis then get some experience good luck;)
 
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