June 2011 2391 exam

[Richard]

Did any of you sit it? I didn't think it was TOO bad, couple of questions I was a little unsure of but overall ok. How did you guys find it? I can never think of the bloddy questions afterwards!

 

[72-van]

Yes ...what was the right answer to the plastic conduit one ??

 

[72-van]

what was the right answer to the rcd socket one ?

i put something like bs7671 req all sockets for use by ordinary persons to be rcd protected

 

[kennydeeee]

Polarity all switches fuses and single pole devices connected in the line conductor only- ensure centre contact of Edison screw lampolders connected in the line conductor only exception e14 and e27 - ensure all sockets and accessories are connected correctly

 

[kennydeeee]

Community centre is for the use by the general public (ordinary persons) so sockets would require additional protection hope I got a mark for this

 

[NEV]

Polarity all switches fuses and single pole devices connected in the line conductor only- ensure centre contact of Edison screw lampolders connected in the line conductor only exception e14 and e27 - ensure all sockets and accessories are connected correctly[/QUOTE

Did you answr the question on the containment system? Was this referring to the check list in GN3 on trunking and conduit.

 

[kennydeeee]

The ka rating on the mcb think I said to change for a mcb with a higher breaking capacity

 

[NEV]

discribe what you would check for on the pvc conduit and trunking

discribe 4 items to check for on the armoured installation useing the sense of touch

discribe the insulation resistance value effects on between live conductors on a switched sput containing neon lamp switched in the off position

explain why the dno cant give values on a tt system

what earthing arrangment applies to external earth fault values of 0.35,0.8,21 ohms

cant think of anymore

What inspection is to be carried out on a severely over loaded installation
What areas would you be most concerned with during the inspection.

 

[kennydeeee]

I answered check properly fixed using sence of touch ( give it a shake ) ensure all lids are in place visual inspection correct position and number of boxes for easy draw of cables visual inspection not sure if that was the Answers they where looking for but thats what they got lol

 

[kennydeeee]

For this one periodic inspection check maximum demand cables selected for current carrying capacity and volt drop bound to be worth 1 mark

 

[Richard]

As many are talking about the volt drop question the correct answers were: 3% for lighting from a public distribution system (so 6.9V of 230V), 8% for the 3 phase motor supplied from a (private) factory generator (so 32V of 400V, I think it was 400V), 5% for the immersion heater in a domestic home (supplied from a public distribution system so 11.5V of 230V). I think I remember these in order. Percentages for volt drop can be found in appendix 12 of BS76 71 Table 12A

What made you think it was supplied by a private generator?

 

[72-van]

i bet they wanted an part answer saying that it was securely fixed to the wall with adequate clips and supports...pity i never wrote that ..

 

[joe_berks]

i put check ends are bushed and reamed , radii of bends for conduit. protected against mech. damage. securely fixed.

IR i answered 'no effect'

earthings arrangement i said tn-c-s , tn-s and tt

what do you think is that right ?

 

[SirKit Breaker]

think i got the voltage drop calcs for the motor circuit up put 5% but think its 8% how long dose it take for the results to come through

6 to 8 weeks mate. hope you passed i know it is tough.

Cheers..........Howard

 

[joe_berks]

in regard to the question 'what two test currents on a 100mA RCD' i answered 1x and 5x ... well just looked at my tester (fluke 1653) and set to 100mA . doesnt give an option to test at 5x so that answers that one . thing is though, when i select 1000mA RCD , i can test that at 1/2x or 1x !!!

 

[72-van]

I might be wrong but dont you only need to do the 5 times test when you are testing a rcd/rcbo giving additional protection .so I delta N value of less than or equal to 30 ma ..

72-van