RDU Mk2 Installation & Programming Manual
Document No: LT0499
Configuring An RDU
Page 5-4
8 April 2015
Issue 1.02
5.3.2
BATTERY/CHARGER CALCULATIONS
The recommended order of calculations is as follows:
1.
Calculate the RDU quiescent load (Iq) from the figures given in Sections 3.3.1 for a
MAF configured RDU or 3.3.2 for a Non-MAF configured RDU. Calculate In
separately, where In is the external non-alarm, non-battery backed load on the RDU
PSU (e.g. door holders).
2.
Calculate the RDU alarm load (Ia) for 2 zones in alarm from section 3.3.1 or 3.3.2 as
appropriate. (Include all external loads e.g. bells, relays).
3.
Calculate the 5 hour/0.5 hour battery capacity for the charger requirement as follows:
Cap (5 hr) = (5 x Iq) + (0.5 Ia x 2) Ahr
= 5Iq + Ia where
Iq = quiescent current
Ia = alarm current
4.
Find the greater of Iq + In, or Ia. Calculate the power supply/charger requirement (Ic)
as follows and check that it is less than 3A. (If greater a 6A charger is required).
Ic = I + Cap (5 hr)/(24 x .8) where I is the greater of Iq + In, or Ia.
5.
Calculate the battery capacity as follows:
Cap (24 hr) = (24 x Iq + Ia)
Select a battery which has a rated capacity (i.e. 20 hr rating) at least 25% higher than
this).
5.3.3
EXAMPLE BATTERY/CHARGER CALCULATIONS
MAF RDU BATTERY/CHARGER CALCULATION EXAMPLE
An example MAF RDU has the following configuration:
MAF/PSU module, no 16 Zone Display boards
350mA of door holders off +VNBF
Ancillary relay 1 (on the MAF) switching a 24V, 100mA load
A Bell circuit with 0.75A of 24V bell load.
Calculate the required battery capacity and check the power supply load.
Steps
1.
The quiescent load (Iq) for the mains fail situation is:
53mA (MAF configured RDU, standby relay held)
Use Iq ~= 0.055A.
The quiescent load for mains on is Iq plus the door holders (In = 0.35A), i.e., 0.40A.