An Air Handling Unit $($AHU$)$ installed on the rooftop of a building has a total of $30$ kW maximum demand, $0\mathrm{.}90$ power factor, $400$ V three$-$phase power source, with $4$ Cored $($RYBN$)$ armoured XLPE incomer cable. The XLPE cable inside the building is clipped direct to a non$-$metallic wall with $2$ other cables with an expected ambient temperature of $35$ degrees Celsius. The XLPE cable outside the building is installed on perforated cable tray support touching $3$ different cables. The outside ambient temperature is $45$ degrees Celsius.

Determine the following:

A$.$ Design Currents $I_b$ in Amp and MCB Current rating $I_n$ in Amp

$[2$ points$]$

$[1$ point$]$

Note: Standard $I_n$ for MCB: $6,10,16,20,25,32,40,50,63,80,100,125$Amp

B$.$ Tabulated Current $=I_{t,\text{m}\text{a}\text{x}},I_{t,\text{o}\text{u}\text{t}},I_{t,in}$in Amp SHOW YOUR TABLE for the $Ca,Cg,Ct,$etc.

$[3$ points$]$

Cable current carrying capacity $=I_2$ in Amp

$[1$ point$]$

Cable cross$-$sectional area $S$ in $m{m}^2$

$[1$ point$]$

C$.$ If the Voltage drop $($VD$)$ is $1\mathrm{.}804$ Volts, determine the total cable length $(L_{\text{t}\text{o}\text{t}\text{a}\text{l}})$ needed to serve this AHU from the source to the rooftop $($inside plus outside$).[2$ points$]$

Solutions & Answers: