2330 206 C&G Practical Help! *SOLVED*

[EKC]

Hello,

Basically I've done the most of my practical exam today, I just have to finish of wiring and testing tomorrow.

My question is that on one of the pages after testing it asks you 2 questions (Yes or No) and to state a reason why.
I can't remember off the top of my head what the questions were but it was something like, Why use a MCB Type B 20A for your power circuit and why use MCB Type B 6A for your lighting circuit.

Something along the lines of that or something like 6kA I don't know. I think I know why it's type B because by using type B there is little or no Surge.

If anyone has done this practical exam and can help me please reply. Thanks

PS: It's Page 9 I think.

EDIT:

I just remembered the questions, they are as followed.

Power Circuit - 20A, 6kA, Type B
Lighting Circuit - 6A, 6kA, Type B

Then after you fill the table out like above it says something like,

Is the MCB 20A suitable for the power circuit?

Yes/No

Give Reason:

Is the MCB 6A suitable for the lighting circuit?

Yes/No

Give Reason:

I'm not sure how its exactly laid out but it's similar to the above.
Also the Power circuit is 3 double socket outlets on a radial with a single socket outlet as a spur, wired using twin and earth.
The Lighting circuit is 2 baton holders with 2 switches, wired using singles.

So can anyone help me further now?
Thanks.

 

[EKC]

Re: 2330 206 C&G Practical Help!

No-one can help me?

 

[mamamaka]

Re: 2330 206 C&G Practical Help!

Type b cos its domestic and 6amp is a lighting radial circuit and 20amp is a cooker or similar depending on the rating

 

[JUD]

Re: 2330 206 C&G Practical Help!

Your question is a bit vague but I'll try and help.

The size of the MCB is chosen after the load has been determined. 6A MCBs are the norm in domestic lighting circuits as they usually have minimal loads attached to them. This doesn't mean that you can't use a bigger MCB for a lighting circuit, you just have to ensure the csa of the cable is sufficient for the size of MCB you're using.

Type B MCBs are used when there is not expected to be any high start-up currents such as you get with some motors etc. (not very likely in a domestic situation).

 

[EKC]

Re: 2330 206 C&G Practical Help!

Thanks for your help sorry for not being that clear in the first place.
I will just try and see what can do tomorrow using my on-site guide to help me.
Hopefully I won't fail if I get the 2 reason's wrong.

 

[EKC]

Re: 2330 206 C&G Practical Help! *UPDATED* HELP!

Just updated original thread, can anyone help me further now?

 

[JUD]

Re: 2330 206 C&G Practical Help! *UPDATED* HELP!

Hello,

Basically I've done the most of my practical exam today, I just have to finish of wiring and testing tomorrow.

My question is that on one of the pages after testing it asks you 2 questions (Yes or No) and to state a reason why.
I can't remember off the top of my head what the questions were but it was something like, Why use a MCB Type B 20A for your power circuit and why use MCB Type B 6A for your lighting circuit.

Something along the lines of that or something like 6kA I don't know. I think I know why it's type B because by using type B there is little or no Surge.

If anyone has done this practical exam and can help me please reply. Thanks

PS: It's Page 9 I think.

EDIT:

I just remembered the questions, they are as followed.

Power Circuit - 20A, 6kA, Type B
Lighting Circuit - 6A, 6kA, Type B

Then after you fill the table out like above it says something like,

Is the MCB 20A suitable for the power circuit?

Yes/No

Give Reason:

Is the MCB 6A suitable for the lighting circuit?

Yes/No

Give Reason:

I'm not sure how its exactly laid out but it's similar to the above.
Also the Power circuit is 3 double socket outlets on a radial with a single socket outlet as a spur, wired using twin and earth.
The Lighting circuit is 2 baton holders with 2 switches, wired using singles.

So can anyone help me further now?
Thanks.

You say the power and lighting circuits are wired in T&E and singles respectively. To say wheather or not the MCBs are suitable you'd need to know the csa of the conductors 1.5mm², 2.5mm² etc.

The MCB is there to protect the cables from overload and/or overcurrent so the current-carrying-capacity of the cable should be greater than or equal to the MCB rating.

 

[EKC]

Re: 2330 206 C&G Practical Help! *UPDATED* HELP!

You say the power and lighting circuits are wired in T&E and singles respectively. To say wheather or not the MCBs are suitable you'd need to know the csa of the conductors 1.5mm², 2.5mm² etc.

Twin and earth are 2.5mm singles 1.5mm

So I would say they are suitable but I don't know why? The trouble is what do I put for a reason. I know part of it is that the MCB is type B because there is little or no surge but I don't know what else to put.

Thanks

 

[JUD]

Re: 2330 206 C&G Practical Help! *UPDATED* HELP!

Assuming both circuits are installed to Ref. Method C (clipped direct) and no de-rating is required then they'll be fine.

2.5mm² Ref. Method C is good for 27A. As this is greater than the MCB rating then it's fine.
1.5mm² Ref. Method C is good for 19.5A. Again this is greater than 6A so jobs a goodun.

Type B is fine for both as there are no high start-up currents expected.

 

[EKC]

Re: 2330 206 C&G Practical Help! *UPDATED* HELP!

Assuming both circuits are installed to Ref. Method C (clipped direct) and no de-rating is required then they'll be fine.

2.5mm² Ref. Method C is good for 27A. As this is greater than the MCB rating then it's fine.
1.5mm² Ref. Method C is good for 19.5A. Again this is greater than 6A so jobs a goodun.

Type B is fine for both as there are no high start-up currents expected.

So for example I put this:

Yes
Reason: The 20A MCB is suitable because the 2.5mm² Twin and Earth is good for 27A which is greater than the MCB rating.
Type B is suitable because there is no high start-up currents expected.

Yes

Reason: The 6A MCB is suitable because the 1.5mm² singles are good for 19.5A wich is greater than the MCB rating.
Type B is suitable because there is no high start-up currents expected.

I think that should be fine, thanks so much for your help!!

 

[JUD]

Re: 2330 206 C&G Practical Help! *UPDATED* HELP!

So for example I put this:

Yes
Reason: The 20A MCB is suitable because the 2.5mm² Twin and Earth is good for 27A which is greater than the MCB rating.
Type B is suitable because there is no high start-up currents expected.

Yes

Reason: The 6A MCB is suitable because the 1.5mm² singles are good for 19.5A wich is greater than the MCB rating.
Type B is suitable because there is no high start-up currents expected.

I think that should be fine, thanks so much for your help!!

You could maybe also mention that the load currents will be less than the rating of the MCB (especially on the lighting circuit). 2 lamps (100W each) = 200 ÷ 230 = 0.87A.

Maybe word your answers better than what I put. Something along the lines of "The current-carrying-capacity of 1.5mm² is 19.5A Reference Method C....."

 

[EKC]

Re: 2330 206 C&G Practical Help! *UPDATED* HELP!

You could maybe also mention that the load currents will be less than the rating of the MCB (especially on the lighting circuit). 2 lamps (100W each) = 200 ÷ 230 = 0.87A.

Maybe word your answers better than what I put. Something along the lines of "The current-carrying-capacity of 1.5mm² is 19.5A Reference Method C....."

Im not that "bright" so if I put that he would know that isn't my answer, I'm sure with the example I put above from your amazing help! will do the trick! Thanks so much again!