Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 12 Page 61 of 265
Therefore for our theoretical junction (Figure 13) the total average controller power
is:
1 x Controller 40W
2 x Siemens ST4R/ST4S Detectors 6W
Total Average Controller Power is: 46W
3.14.6.4 Total Average Junction Power
For the total average junction power to aid local authorities with running cost
estimates, the total average lamp power must be added to the controller average
power.
Total average Junction power is calculated as follows:
Total average lamp power
179W
Controller power 46W
Total Average Junction Power is: 225W
If it is required to make an estimate of running costs which include the period of time
that the signals are dimmed this can be approximated as follows:
Total Average Junction Power (Dimmed) is:
Total Average
Signal Power
(Less Reg. Signs)
x
Dimmed
Lamp Power
+
Total
Reg. Signs
+
Total Average
Controller Power
Bright
Lamp Power
Therefore, for the theoretical junction:
(179W – 7W) x
3.5 W
+ 7W + 46W
12 W
Total average Junction Power (Dimmed) = 103W
Note
The controller power should also include any additional equipment
supplied by the controller. This may include, for example, OTU, OMU or
Auxiliary detector power supply.
3.14.7 Detector Power Supplies
Detectors are normally powered from the detector supply on the HPU card, which
provides rectified and earthed -24V rms at 2.8A DC. If more current is required, then
power the additional detectors from an additional -24V 2A (50VA) or 6.6A (160VA)