Need answer to these questions - 2330-302

[mani]

Sort it out tomorrow for you if no one else has.

thankyou sintra

 

[Sintra]

Could you please also try these??

Questions 1) A six way consumer unit has five circuits connected to it, the sixth way is left as a spare. An insulation resistance test carried out on the individual circuits (L-N to earth) produces the following results:

Way - 1, 2, 3, 4, 5, 6
Megohm - 60, 20, 10, 60, 60, spare

　
a) Determine the overall value of insulation resistance if all circuits were tested together. Show or explain your working.

Formula 1 / Rt = 1 / R1 + 1 / R2 + 1 / R3 + ....
1 / Rt = 1 / 60 + 1 / 20 + 1 / 10 + 1 / 60 + 1 / 60
Rt = 5 M ohms

b) State the effect on the overall value of connecting an additional circuit to way 6 in the board.

This will decrease the Rt

12) Calculate the size of metal conduit required to contain 6x6mm2 single core pvc insulated cables. The total lenght of the conduit run is 10 metres but there is a draw in box exactly half way along the conduit run. There are two bends either side of the draw in box (4 bends in total). Show all working.

Factor for a 6mm cable in conduit = 58
6 x 58 = 348
Cable factor = 348

5M run between boxes with 2 bends the factor for 20mm is 196 so this is less than the cable factor so unacceptible.
For 25mm the factor is 358 so is acceptible as it is higher than the cable factor.
　
13a) A single phase load of 30 amperes is supplied by 6mm2 single core 70oc thermoplastic pvc cables in conduit and trunking. If the cable is 24 metres long, calculate the circuit voltage drop.

Formula
Volt drop = ((mV/A/m) x Ib x L) / 1000
Volt drop = 7.3 x 30 x 24 / 1000
Volt drop = 5.256 V

b) If the above cable is subjected to a fault current of 125 A which causes disconnection in 5 seconds, what is the minimum size cpc which could be used.

Adiabatic equation
S = √ Isq x t / k
S = √125sq x 5 / 115
S = √78125 / 115
S = 279.5 / 115
S = 2.43
Minimum size of cpc = 2.5mm
　
15) Draw a fully labelled earth fault loop impedance path for a TN-C-S system for a fault on a fized load within the installation.

Have a look here

16) Draw the layout of a domestic intake position from the supply authority cut out to the consumer unit. Include all live conductors correctly identified in their appropriate positions.

Hope this helps

 

[Guest123]

Hope this helps

You have the patients of a Saint my friend.

 

[Sintra]

It keeps me out of the pub.

 

[Guest123]

It keeps me out of the pub.

I get what you're saying, I think my mrs would rather I was in the pub because at least I'd be talking to people that I could see.

She thinks that all you lot are imaginery and that I'm a very sad person who talks to himself for hours on end.

 

[mani]

Thanks sintra for all your help. appreciated mate! It is really nice to know the answer to them and thankyou for sharing your knowlegde with me.

 

[GrannySmiff]

I just did that exact paper and got a distinction.

 

[Phil]

I get what you're saying, I think my mrs would rather I was in the pub because at least I'd be talking to people that I could see.

She thinks that all you lot are imaginery and that I'm a very sad person who talks to himself for hours on end.

i am sure mine thought i was on some dodgy site at one point, so i moved to the sofa with the laptop and annoy her typing that will teach her to watch rubbish tv programmes