Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 12 Page 36 of 265
Intersection’s Power Requirements for Running Costs Estimate
2.11.3.1 Introduction
The following worked example is based upon a 230/240V mains’ supply.
Firstly the Total average lamp power for the junction is calculated. Secondly the
Total average lamp power is added to the Total average controller power. This gives
the Total average junction power, which a local authority may use to estimate
running costs.
Total Average Lamp Power
Total Average Junction Power = +
Total Average Controller Power
2.11.3.2 Total Average Lamp Power
Total average lamp power is calculated as follows:
For every signal head, only 1 lamp is illuminated on average (at 63W assuming HI
lamps), plus every WAIT indicator is illuminated at 40W and every Regulatory Sign
is illuminated at 30W.
Therefore, considering our theoretical junction (Figure 6), we have:
12 signal heads each with 1 lamp at 63W (12 x 63w)
756W
4 wait indicators illuminated at 40W (4 x 40w) 160W
One Regulatory Sign at 30W (1 x 30w) 30W
Total Average Lamp Power is: 946W
2.11.3.3 Total Average Controller Power
Total average controller power is calculated as follows:
Average Controller power + Average Detector Power.
A basic controller with dimming is rated at 47W, and for the purposes of this
calculation Siemens ST4R/ST4S detector cards are rated at 3W/card. See section
2.11.1.
Therefore for our theoretical junction (Figure 6) the total average controller power is:
1 x Controller
47W
2 x Siemens ST4R/ST4S Detectors 6W
Total Average Controller Power is: 53W