Electricity + Control February 2018

round up

CABLES + ACCESSORIES

Table 3: Extreme scenarios ‘Most favourable case’ and ‘Least favourable case’ and the resulting geometric average for a private household; annual line losses for all three cases.

still not charge the main fuse up to its limit. In residential buildings, the ubiquitous availability of electrical energy prevails over the volume actually used. As a result, the residential design is differ- ent from those in the office under consideration. The main fuse does not provide anywhere near as much power as the final circuits could distribute. This was taken into account accordingly in the cal- culations of the tables reproduced here. The po- tential energy saving that exists in this case had already been partially converted during the origi- nal planning of the office in question. Indeed, al- though the final circuits had been provided with a conductor cross-section of 1,5 mm 2 , they had only been fused at 10 A. This is probably down to the limitation of the voltage drop on the cables, some of which are quite long. So the stringent require- ments to limit the voltage drop result in energy savings. This can be seen as a positive side effect

13 times. An energy loss can therefore be calcu- lated for the final circuits of minimum 401 kWh/a (0,439%) and maximum 2 625 kWh/a (2,87%), corresponding to 1 026 kWh/a in the geometric mean between the two: That looks more like an actual energy saving. Be- cause of the significantly higher utilisation of the floor distribution, the spread between the minimum and maximum scenarios – and therefore the uncertainty – is correspondingly less. Admittedly, here too the cable lengths could only be estimated and were tak- en into account as a general average, but this does not influence the payback period (cf. Approach 2), since the costs of both material quantities and ener- gy losses are proportional to the cable length. The distribution is also different from those in residential buildings, in accordance with the pur- pose. The limiting factor is the number of circuits; even if they were all used at full load, they would

Electricity + Control

FEBRUARY 2018

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