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IQ251 Controller Data Sheet TA102315 Issue 4, 8/10/08
Data Sheet IQ251
FIRMWARE
Communications: When operating as part of a Building Management System, the IQ251 will be connected to other devices using the
IQ system Network. This means that information within the IQ251 can be accessed using one of the IQ system supervisor programs, or
passed to other IQ controllers using inter-controller communications, enabling the sharing of information across the whole system.
When connected to the network the controller can use up to 3 different addresses. One address is for the controller itself (set by front
panel switch) the second and third are optional, and are for the locally connected supervisors (supervisor port address), (ndp port
address). Thus a locally connected supervisor has its own network address when connected to the network using the controller.
The controller’s address is set by a switch, and the supervisor and ndp port adresses are set up in the strategy configuration
(address module).
Battery Status: The IQ251 has a battery status checking circuit that checks the battery on power up and thereafter every midnight
and sets byte 506 bit 0 if the voltage has falls below a threshold value. This bit being set indicates that the battery needs to be changed.
It should be used within the strategy to generate an alarm (e.g. critical alarm). The battery should be changed after the first indication.
The battery will have a typical life of 10 years at 20 °C (68 °F). It is recommended that the battery is replaced every 5 years.
HARDWARE
Unit: The IQ251 has a metal chassis and a metal front cover. The
I/O modules are of aluminium extrusion. The I/O modules are fitted
to the controller by snapping off a section in the cover and removing
the relevant side plate. The module connector then slides into a
socket on the controller. There is an option to fit a 16 terminal earthing
(grounding) bar below each I/O module for cable screens (Part/
LA102359K). Cable access is using holes in the rear plate, or from
top or bottom, cables can be run down the central column behind
the controller board. Cleats are fitted to the rear plate to facilitate
cable mounting. There is a 25 Way D type knockout on the bottom
of the front panel for RS232 connection to an auxiliary node, and
a circular knockout for M20 gland or grommet for internetwork,
PSTN, ISDN or Lon cables. If required the IQ251 can be fitted in an
IP55 metal enclosure (ENCLS).
Connectors: Two part connectors are used throughout to facilitate
wiring. A busbar is provided for screen termination.
Power: 230 Vac 50/60 Hz, 24 Vac 50/60 Hz, or 24 Vdc. The 24 Vac
input power must be isolated and can only power 1 controller. The
24 Vdc input power may be earthed (grounded) but polarity must be
correct; it can power several controllers in parallel.
Fusing: The controller has no replaceable fuses; protection is
providedbymeans of a self-resetting thermally protected transformer.
The 24 V ac or dc versions have a 4A replaceable 1¼” fuse fitted
in line of input power cable inside the unit and a solid state multifuse.
The I/O modules are also individually protected against short circuits.
Indicators: LED indicators for receive and transmit network current flow
(RX, TX) and network OK ( ), also for power ( ), all I/O channels ( ),
and watchdog ( ). See specification section for details.
Network: The network terminals facilitate connection of 2 or 4 wire
cables. The standard IQ system node features are included (TX,
RX, and network OK, , indicators, bypass relay, and network alarm
generation). There is also the facility for connection of a supervisor
and integral network display panel to the network using the controller
without the need for additional node controllers.
Note that the IQ251 does not have a balanced line transmitter
like other IQ2 series controllers and this may result in reduced
network resilience.
Address/Baud rate switch: The address on the Lan is set by
poles 1 to 7 in range 1, 4 to 9, 11 to 119 and must be unique on
the Lan. The baud rate is set by poles 8 to 10 in the range 1k2,
9k6, 19k2 and must match the other nodes on the Lan. The
address/baud rate switch may also be used to perform a strategy
cleardown; this is done by setting all the address/baud rate poles
to zero before power up (see Installation Instructions, TG103483
sheet 4 and IQ Configuration Manual Addendum). For this reason
the address should normally be set non-zero.
These loads can be calculated as follows:
Input module
8 digital inputs @ 8 mA per channel
8 analogue inputs @ 20 mA per channel (thermistor and
voltage inputs can be ignored)
Max total for whole I/O module = (8x8)+(20x8) = 224 mA
Output module
8 analogue outputs @ 20 mA per channel
Max total for whole board = 20x8 = 160 mA
8 digital outputs @ 24 mA per channel
Max total for whole I/O module = 24x8 = 192 mA
Integral Node (e.g. TMN) = 250 mA.
(For consumption of other nodes see the respective data sheet).
For example:
IQ251 with 4 input I/O modules, 2 digital output I/O modules, 2
analogue output I/O modules, an integral NDP, and an MNC.
How much current is available from the auxiliary output supply?
Current consumed:
4 input I/O modules (all analogues are current) 4 x 224 =896 mA
2 digital output I/O modules 2 x 192 mA=384 mA
2 analogue output I/O modules (at max). 2 x 160 mA=320 mA
1TMN 250 mA
Total 1850 mA
Current available: 2100 - 1850 =250 mA
Battery Backup: Details about the strategy configuration, time
and date, and logged data are stored in RAM. A plug-in lithium
cell provides power to maintain the data in the event of power
failure, or the controller being switched off.
Auxiliary output supply: There is a 24 Vdc auxiliary output
supply provided on the input power board to power external relay
modules, sensors, etc. It is thermally protected and can provide
a maximum of 500 mA. This will normally be available, but if the
IQ251 has a full complement of I/O modules, and an integral
comms node fitted the amount of auxiliary power available for
other purposes will have to be calculated. The 24 Vdc input
power in the IQ251 has 2100 mA available after deduction of
current required for main board and network. This has to power I/O
modules, integral node, and the 24 Vdc auxiliary output supply.
I/O
node
AUX
variable
(e.g. 250) optional
500 mA (maximum)
2100 mA
