HAI Omnistat2 RC-1000, Protocol Manual

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APPENDIX B – Direct Connect Cables
A typical RS-232 port on a personal computer can drive 4 thermostats directly on up to 500 feet of wire.
HAI makes a 10 foot cable, p/n RC-201, with a DB-9F on one end and the thermostat connector on the
other. You can make this cable easily as described below. For more than 4 thermostats or wiring lengths
greater than 500 feet, HAI recommends the RC-202 signal booster to increase the drive capacity of the RS-
232 port and to provide additional surge protection for the serial port. An RC-202 can drive up to 127
thermostats over 10,000 feet of wire.
Direct Connect Cables
Serial ports on most computers have two connector types: DB-9M and DB-25M. To make a cable to
connect one or more thermostats to this port, you will need:
1. One DB-9F or DB-25F connector, depending whether your computer has a DB-9M or DB-25M
connector for its serial port (F stands for female, M stands for male).
2. Four (4) conductor wire. Use 22 to 24 gauge shielded or unshielded, stranded or solid, twisted or
untwisted, the wire type is not critical. Use shielded if your environment calls for running the
communications wire along with power wires, and connect the shield to a good ground at the
computer (do not connect the shield at the thermostat).
Make the connections as follows:
If using a DB-9F connector:
1.
On the DB-9F connector: Connect pins 7 and 8 together. (RTS and CTS)
2. On the DB-9F connector: Connect pins 1, 6 and 4 together. (DCD, DTR and DSR)
3. Connect pin 4 of the DB-9F to the YELLOW connector on the COMM portion of connectors on the
thermostat back housing. (DTR)
4. Connect pin 3 of the DB-9F to the GREEN connector on the COMM portion of connectors on the
thermostat back housing. (TXD)
5. Connect pin 2 of the DB-9F to the BLACK connector on the COMM portion of connectors on the
thermostat back housing. (RXD)
6. Connect pin 5 of the DB-9F to the N/C connector on the COMM portion of connectors on the
thermostat back housing. (GND)
If using a DB-25F connector:
1.
On the DB-25F connector: Connect pins 4 and 5 together. (RTS and CTS)
2. On the DB-25F connector: Connect pins 8, 6 and 20 together. (DCD, DTR and DSR)
3. Connect pin 20 of the DB-25F to the YELLOW connector on the COMM portion of connectors on the
thermostat back housing. (DTR)
4. Connect pin 2 of the DB-25F to the GREEN connector on the COMM portion of connectors on the
thermostat back housing. housing (TXD)
5. Connect pin 3 of the DB-25F to the BLACK connector on the COMM portion of connectors on the
thermostat back housing. (RXD)
6. Connect pin 7 of the DB-25F to the N/C connector on the COMM portion of connectors on the
thermostat back housing. (GND)
7. Additional thermostats are connected in parallel (yellow to yellow, green to green, red to red, and
black to black).
Wiring for additional thermostats can be home run or daisy chained, or a combination of both.
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All Rights Reserved
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