Help with 2382 17th exam

[gazdkw82]

iv been regularly doing some mock exams online in preparation for my exam next week, however there's been a few questions that keep coming up and I can't seem to find the answers. I took screen shots and below are the following questions. Could you help put me out my misery point me in the right direction.

One question mentions earth fault loop impedance of 3.83 but then has a Y with 2 dots above it. I'm not familiar with this. What does it mean?

Got a question "maximum Zs for a BS EN 60898 32A B type circuit breaker protecting a domestic circuit is" --- in the book I get 1.37 but the only possible answers are 1.44, 1, 1.87 and 1.23.

Next one is "if a fault occurs in the HV system, and a magnitude of fault voltage of 430 volts occurs between exposed conductive parts and earth on LV installation. What is the maximum tolerable direction of the fault" -- I really don't know where to find the answer to this one.

Next one "heating units designed to be used underfloor should have a minimum IP rating of" -- again iv searched and searched And I just can't seem to find the answer

Next one is about impulse category. Iv never heard of it, neither can I find it in the book. Any ideas what this could be?

Thankyou

 

[telectrix]

1. the max. Zs is 1.44 as per bgb, but amd.3 corrected this with a 0.95 correction factor, so that gives 1.37.

2. think it should be duration, not direction.

3. i can't find that either, but i'm still on the bgb.

4. no idea.

so that's about as useful as an ashtray on a motorbike, but at least i tried.

 

[gazdkw82]

So why are the mock exams listing answers that are not actually in the 17th amd3. Will the real exam list answers pre correction factor?

 

[FatAlan]

Where are you getting the online questions from? I've used several sources and some are better than others in respect of questions and giving the correct answers. Make sure you know your way around the appendices.

 

[FatAlan]

Try looking in the OSG and using the cross references back to BS7671.

 

[gazdkw82]

So will I need to be cross referencing on the exam?

Iv done a few different ones, ----------- and another one (can't remember the name) but it actually has the clock ticking down.

I'm trying to get to grips with the appendixes however I am a little confused on which cable refers to what table. Like what does the discretion actually mean (70c thermoplastic etc etc)

 

[FatAlan]

Unfortunately you can't cross reference in the exam but I thought it may assist in tracking down answers to your specific questions above so you'll know for future reference.

 

[gazdkw82]

Will the real exam have answers that have no correction factor, or will they be relevant to the 17th edition

 

[FatAlan]

I would like to think that in the real exam the question will be specific enough to give you a clear hint on whether a correction factor is needed. You need to be very careful when reading the question.

 

[FatAlan]

Look at appendix 14 page 452 where it tells you to multiply by 0.8 to get the measured values that are tabulated in the OSG

 

[RM11541]

don't know how much help this is:

floor heating systems: p295, section 753.522.4 refers to presence of solid foreign bodies (AE).
then check degrees of protection, AE needs IPXX.

impulse category might be referring to classification of equipment for overvoltage protection: p97 tables 44.3 and 44.4.

 

[Richard Burns]

don't know how much help this is:

floor heating systems: p295, section 753.522.4 refers to presence of solid foreign bodies (AE).
then check degrees of protection, AE needs IPXX.

impulse category might be referring to classification of equipment for overvoltage protection: p97 tables 44.3 and 44.4.

Good answer, I like it.

For floor heating systems
753.512.2.5 states IPX7 and appropriate mechanical protection for floor heating systems.

gazdkw82 any exam you take for real will be to the current regulations i.e. at the moment AMD3.
Any question will either refer to testing to get a result (i.e. at ambient temperature) or metion temperatures to show what is required.

Cables that have thermoplastic are normal PVC cables and have PVC insulation which is rated to 70°C.
Cables that have XPLE (commonly) insulation are a thermosetting plastic and are rated to 90°C.
The sheath material is generally immaterial for temperature rating as it will not expose live parts if it melts.
The armoured is SWA or other wire armour cables (again with the temperature rating based on the insulation of the cores.
However if the equipment to which the cable is connected has a lower temperature rating then the lowest rating should be used for calculations as the conductors cannot be permitted to heat up to 90°C if it will cause the audiometer to be dangerous.