Adiobatic

[Guest123]

I have it on a PDF......too large to upload here though.

PM me your e-mail if you like and I'll send it on.

 

[ringer]

Re: Adiabatic

Please confirm my calcs and methods, am calculating to confirm correct selection of csa for cpc

Line and neutral csa is 2.5mm^2 and csa of cpc is 1.5mm^2
Singles in conduit from a Eaton MBH120. This is a 20A MCB rated for short circuit current of 10kA.
Zs has been measured at 0.24ohms on 230V nominal supply.
Assuming k=143 and looking for disconnection time of 0.1s

Using the adiabatic S=sqrt(I^2t)/k and calculating from the above measured values:
PEFC = 230/0.24 = 958A
S = sqrt(958^2 * 0.1)/143 = 2.118 which indicates required csa of cpc = 2.5mm^2

Now using manufacturers data from tables provided:
PSSC = 10kA (because mcb is rated for this)
According to tables for 20A mcb with PSSC of 10kA the I^2t value is 33000
S = sqrt(33000)/143 = 1.27 which indicates required csa of cpc = 1.5mm^2

So is the use of 1.5mm^2 for the cpc correct?

 

[Guest123]

Manufacturers data can always be used.

Indeed when I did my 2400 we were encouraged to look it up and use their figures as it makes for a more economical design (only after we had done all the adiabatics though)