C&G NVQ L3 2357 Unit 304 Task B

[alextrician]

hello there.

I am just about to finish my second assesment and i am stuck on a few questions. I think I know the answer but not sure. So...the questions are:

1) The proposed design of the installation includes the following protective devices:

BS EN 60898 type d mcb for the MIG welder (rated 16A)

MCCB rated @ 125A for the distribution circuit to the DB2.

Determine using manufacturer's information whenever discrimination will be achieved

2) determine the minimum size of cpc for each of the circuits giving consideration to disconnection times and thermal constraint.

circuit 1: 5kW/400V 3 phase machine; actual Zs=0.59ohms; Ia=430.10A

circuit 2: 12kW/400V 3 phase machine; actual Zs=0.5ohms; Ia=800A

circuit 3: 11kW/400V MIG Welder actual Zs=0.5ohms; Ia=800A

circuit 4; 3kW/230V water heater (i did not work this out yet)

3) Circuit 4 should be wired in MI cable for the total lenght or the circuit? Can I run the MI cable in the same trunking with the other 3 circuits above applying the corection factor Cg of 4 cables or in a separate containment?.

I also had a go on the questions and I come up with this:

1) the discrimination will not be achieved because the 16A circuit breaker has higher breaking capacity due to high staring currents (type D)

2)using the adiabatic equation circuit 1 has 1mm cpc cable & 1.5mm live conductors

circuit 2 has 6mm cpc cable & 6 mm live conductors

circuit 3 has 6mm cpc cable & 4 mm live conductors

For the calculation I used the t=0.4 ses K=115

S=(square root of)I squared X t all divided by K

Help and sugestions are well come.

Thank you very much

Alextrician

 

[a1]

Show us what you done so far, mate, then the guys and girls will through them and tell you if you are correct or not. If not correct, they will help you.

 

[alextrician]

Show us what you done so far, mate, then the guys and girls will through them and tell you if you are correct or not. If not correct, they will help you.

hopefully i will upload (i don't know if possible) my entire task b with q & a tonight or 2mora morning for the guys to have a look at it.

Thanx for reply

alextrician

---------- Post Auto-Merged at 16:27 ---------- Previous post was made at 16:26 ----------

hopefully i will upload (i don't know if possible) my entire task b with q & a tonight or 2mora morning for the guys to have a look at it.Thanx for reply

alextrician

the reason is that is not finished yet

 

[Sidewinder]

Any use?

 

[alextrician]

View attachment 3834Any use?

thank. I really apreciate it. I've got all tables in the appendix 3 of the regs book, but i don't know how to use them to figure the disconnection time or that is the purpose of these tables.

---------- Post Auto-Merged at 02:58 ---------- Previous post was made at 02:12 ----------

Show us what you done so far, mate, then the guys and girls will through them and tell you if you are correct or not. If not correct, they will help you.

1.a) Determine, using the aiding drawings the minimum csa of live conductors suitable for current carrying capacity and the volt drop for the following circuits. The rating factor for grouping are based on the above for circuits within the same containment system with the ambient temperature of 25C

In order to determine the cross sectional area of the live cables and volt drop for all the circuits, we need to find out the current drawn by the each particular machine, the rating of protective device and type, a method of installation, any available correction factors and the maximum and the actual voltage drop.

So