A friend in need

[virtualcom13at]

Sorry to ask but i really need help with 5 out of my 61 question TMA, Its driving me mad headbang . I have read over and over the recommended reading and more but I cant seem to find the correct answers and I don't want to put just want i think it is.

My questions are,

1 - When applying a test voltage to an item of class I equipment, a value of 0.1 MOhms is obtained. One possible reason for this low reading could be:

A - progressive failure of the insulation between live conductors and earth

B - progressive failure of the insulation between live conductors

C - an open circuit has occurred within the protective conductor

D - a short circuit between live conductors within the appliance cord set

2 - Whilst carrying out an earth continuity measurement on a 3 kW class I electric fire, the measured resistance slightly increases during the period of test. One possible reason for this increse in resistance could be:

A - degradation of the insulation due to an excessive test current

B - an open circuit in the protective conductor

C - a loose connection at the earth terminal within the mains plug

D - insufficient current supplied by the test equipment

3 - where equipment has a protective conductor current designed to exceed 3.5 mA, one requirment is that the label is fixed adjacent to the equipment primary power connection which includes the wording:

A - possibility of high touch current

B - danger high touch current

C - presence of high touch current

D - warning high touch current

4 - which one of the following types of equipment in shops and offices is considered most likely to develop dangerous faults:

A - movable

B - stationary

C - portable

D - hand-held

5 - which one of the following arrangements would not meet the requirments of the iee code of practice:

A - class I equipment supplied by a 1.5 mm three-core extension lead connected into a 13 A three-pin socket outlet

B - class II equipment supplied by a 1.5 mm two-core extension lead connected into a 13 a three-pin socket outlet.

C - class I equipment supplied by a 2.5 mm three-core extension lead connected into a BS EN 60309-2 socket outlet

D - class III equipment supplied by a two-core flexible cord connected into the secondary of an isolating transformer supplying SELV lighting equipment

please don't hassle me as I am only on the second lesson of a course that after 18 months will only be a domestic installer and I don't claim to be anything else. I have managed to answer the rest of the questions but these certain ones are just doing me in and if anyone would be so kind to help me answer these 5 questions that would be fantastic. Even better if you could give a few words to where I could read about these answers so I can get a better understanding. Maybe a section from my BS 7671 book that I am not noticing.

sorry to ask ray

 

[kme]

What do YOU think the answers might be mate?

oh, and welcome to the forum

 

[paul b b]

Like kme said. Try to answer yourself first and others will put you right.

 

[Doc Hudson]

Welcome to the forum Virtual13at. These questions all appear to be PAT course questions. Which have no relevance or requirement to becoming a Domestic installer with any of the approved schemes, (Napit, Niceic, Elecsa, Bsi)? Most are just reference from the various guidance books for PAT testing or basic science knowledge. I doubt if any are found in BS7671 and none have any relevance to designing, or installing or testing electrical circuits in a domestic property. I am unclear how any of this would assist anyone becoming a Domestic installer? As the other gents have said tell us what answers you would think they are and the reasons why and I think you will get a better response. It is standard practice in many mutli choice questions to have Two answerers that are normally quite clearly wrong, one that could be nearly correct, (to trip you up) and the correct answer. Have another look at your questions see if you can write off the two most unlikely options from each question and see where that gets you.

Doc H.

 

[750Kw]

You will find all your answer in : Code of Practice for In-service Inspection and Testing of Electrical Equipment .

Read that and your answer will show up. HTH

 

[virtualcom13at]

Yeah I have found most if not all the answers from there but they have recommended reading through certain sections of BS 7671 and on site guide as well as code of practice.

Thanks for the warm welcome, here are my thoughts on the questions in question.

Q1 = sorry I am Still stuck on this one

Q2 = C (only reason I could find that would affect the increase)

Q3 = A (will only become live under a fault and touch current also means protective conductor current)

Q4 = D (most likely to develop dangerous faults in all areas and table shows hand held equipment needs the most frequent testing in shops and offices)

Q5 = B (two core cables should never be used with three way pin plugs

time to stop studying as my wife has just served up a lovely sunday dinner

 

[martinxxxxxx]

Hope you have enjoyed you sunday lunch, you are very lucky, kids have sick and poo bug here so it has been cancelled.

Just to give you a hand to get started, here are my thoughts

1 - When applying a test voltage to an item of class I equipment, a value of 0.1 MOhms is obtained. One possible reason for this low reading could be:

D - a short circuit between live conductors within the appliance cord set

We are not measuring this with this test

C - an open circuit has occurred within the protective conductor

This is going to give infinity ohms, so cant be right

B - progressive failure of the insulation between live conductors

The pat tester does not measure BETWEEN live conductors, so this can be right.

A - progressive failure of the insulation between live conductors and earth

We must be getting warm here, this is exactly the fault we are on the look out for when we do this test.

 

[kme]

Q5. Why can`t an item of Class 2 equipment have a 2 core mains lead? The fact that it connects via a 3 pin plug has no relevance whatsoever.

 

[Riggy]

Q5. Why can`t an item of Class 2 equipment have a 2 core mains lead? The fact that it connects via a 3 pin plug has no relevance whatsoever.

I read it as 2 core EXTENSION lead, not mains lead?

 

[virtualcom13at]

Q5. Why can`t an item of Class 2 equipment have a 2 core mains lead? The fact that it connects via a 3 pin plug has no relevance whatsoever.

Hey,

Quote from the code of practice for in service inspection and testing of electrical equipment: Any extension lead that does not have a protective conductor (or earth wire) should be marked as defective and removed from service. (((Extension leads fitted with 3-pin plugs and sockets should never be wired with 2 core cables))) as there will always be the possibility that the lead will be inadvertently used to supply a class I appliance, which as a consequence, would not be earthed.

That where I got my answer from.

---------- Post Auto-Merged at 20:06 ---------- Previous post was made at 20:04 ----------

Hope you have enjoyed you sunday lunch, you are very lucky, kids have sick and poo bug here so it has been cancelled. Just to give you a hand to get started, here are my thoughts

1 - When applying a test voltage to an item of class I equipment, a value of 0.1 MOhms is obtained. One possible reason for this low reading could be:

D - a short circuit between live conductors within the appliance cord set

We are not measuring this with this test

C - an open circuit has occurred within the protective conductor

This is going to give infinity ohms, so cant be right

B - progressive failure of the insulation between live conductors

The pat tester does not measure BETWEEN live conductors, so this can be right.

A - progressive failure of the insulation between live conductors and earth

We must be getting warm here, this is exactly the fault we are on the look out for when we do this test.

Thanks mate that is a very helpful post/reply. thumbs up

---------- Post Auto-Merged at 20:09 ---------- Previous post was made at 20:06 ----------

So can anyone be so kind to tell me if what I have answered so far is correct? ray

 

[kme]

Sorry, I completely missed the words "extension lead" :coat

 

[virtualcom13at]

no probs mate. :^O