Revised 8/14/02 • U253
5
© 2002 Automated Logic Corporation
The U253 has an operating range of 21.6VAC
to 26.4VAC. Whenever possible, connect and
verify power and communications to all
modules before connecting any inputs or
outputs.
1. Remove the U253’s power jumper or place
it in the off position. This prevents the
module from being powered up before
verifying correct voltage.
2. Make sure the 24VAC power source is off.
3. Connect the power wires to the module’s
power terminals labeled 24VAC and Gnd.
4. Turn the 24VAC power source on.
5. Make sure that 24VAC is present at the
module’s power input terminals.
6. Set the module’s address. Refer to
“Addressing” on page 4 for details.
7. Replace the module’s power jumper or
place it in the on position.
When the module turns on, the Run LED
turns on and begins blinking. The Run
LED blinks once every two seconds until
communication is established, then blinks
twice per second when operating
normally. Refer to “LEDs” on page 10 for
more information.
Communications Wiring
There is a special wire available that contains
a pair of 14AWG wires for power and a pair of
22AWG wires for communication. See “Power
Wiring” on page 4 for details.
Note that the communication wire is
unshielded. Shielded cable is not required for
the Unet.
In most circumstances, you should have a
PROT485 within 250 feet of any U-line
module on the Unet for surge protection.
However, depending on the frequency of
electrical surges in your area, the 250-foot
recommendation may vary. For example, if
you have frequent electrical storms in your
area, you may want to use more PROT485s; if
you have few electrical storms, you may want
to use fewer PROT485s. If the entire Unet is
less than 250 feet, place at least one PROT485
at the opposite end of the network from the
UNI. For details about the PROT485, refer to
the
ARC156 CMnet Wiring Technical
Instructions
. Make sure that all modules and
the PROT485 use the same polarity
throughout the Unet. You must use a repeater
after every 32 modules or 3,000 feet.
The Unet baud rate is determined by the UNI
module and is automatically detected by the
U253. You can set or change the Unet baud
rate to 9600 bps or 38.4 kbps on the UNI. The
U253 begins using the new baud rate after ten
seconds.
If the module is not communicating with the
UNI, the module’s color is as follows:
• For WebCTRL systems, the module’s
color is purple.
• For SuperVision systems, the module’s
color is coral.
1. Remove the module's power jumper or
place it in the off position.
2. Check the Unet communication wiring for
shorts, grounds, or opens.
Figure 3. Figuring Maximum Number of Modules
Figure 4. Example of Figuring Maximum Number
of Modules
VA (transformer)
VA (module) + VA (accessories)
Maximum #
of modules
(rounded down)
=
100VA
9VA + 6VA
=
6.67 or
6 modules maximum
