B573 User Manual
Revision 1.2, Issued 5/15/08
277 · West Main Street· Niantic, CT · USA · 860-739-4468 · www.inncom.com
10
IMPORTANT
:
•
Each B573 FLN5 COM Port (COM_A and COM_B) can typically support up to 50 RS-485 “room gateway
device” connections. Therefore 100 total connections per B573. These “room gateway devices” include:
01-9560 E528 Thermostat
TCC
B485
X485
K592C
•
The FLN5 RS-485 twisted pair wiring is polarity sensitive. The two wires that make up the pair are
referred to as the “
A
” wire and the “
B
” wire. You must maintain consistency when connecting the RS-485
wiring pair as shown in the image on page 9 (ie A to A and B to B in all of the terminations).
•
The wiring used for the RS-485 wiring should be twisted pair cable such as CAT5 or similar. Typical
wiring used is 22-24 AWG STP but this will depend on the length of the cable runs. The specified
maximum cable lengths for RS-485 is 4000 feet, but this may be shorter depending on quality and type of
twisted pair wiring used and the number of devices connected.
•
Before making any actual termination between the RS-485 pair coming from a particular room and the
B573 COM port , verify the pair has no shorts or excessive voltage present that may indicate the wiring
pair has a problem that could damage the B573 when connected.
A Fluke meter (or similar) should be used to check the RS-485 pair from a particular room before
connecting it to the punch down block or “daisy chain” wiring connected between rooms. This check
should include measuring the resistance across “
A
” and “
B
” to verify a dead short does not exist and
measuring both AC and DC voltages across the RS-485 pair (“
A
” wire to “
B
” wire) AND from the “
A
” wire
to Earth ground and the “
B
” wire to Earth ground.
Typical Expected Values:
Resistance “A” to “B”
: Greater than 1Mega Ohm (meter may indicate “open”)
AC Voltages
: With meter set to measure AC voltage, there should be
NO
discernible AC voltage from
A
to
B
,
A
to Ground or
B
to Ground. Any AC voltage > 100-200 mV AC is suspect and should be
investigated.
DC Voltages
: With meter set to measure DC voltage the following typical voltages are expected with the
RS-485 wiring pair connected to the Room Gateway device ONLY (ie the device has not been connected
to any other room wiring pairs at the punch down/daisy chain or has not been connected to the B573
COM port).
Room Gateway Device
“A” to “B”
“A” to Ground “B” to Ground
01-9560 E528 Thermostat
3.8 VDC
4.2 VDC
0.4 VDC
TCC
0.28 VDC
0.32 VDC
0.04 VDC
B485
1.0 VDC
1.0 VDC
0.0 VDC
X485
3.8 VDC
4.2 VDC
0.4 VDC
K592C
1.0 VDC
1.0 VDC
0.0 VDC
