TEMPTRAC INTERFACE GUIDE, GATEWAY SETUP AND POINTS LIST
Page 4 of 30
PV7069-T 03/17
Part number 129209
TEMPTRAC PROTOCOL
The MODBUS RTU protocol is well established industry protocol and technical references for this are
readily available on the Internet.
Data Types Used
The TempTrac only uses one data type
Holding Registers (40001
– 49999) Read/Write
Other data types such as Coils are not implemented in the TempTrac control.
Only the data points in the POINTS LIST should be accessed.
Physical Layer RS-485
MODBUS RTU uses the physical layer RS-485.
RS-485 (EIA-485): A 2 wire (twisted pair) multi drop network. Each device can send data by holding positive
and negative voltage on the line and reversing polarity on the 2 wires. When no devices are transmitting,
the line will be tristate. The recommended arrangement of the wires is as a connected series of point-to-
point (multi-dropped) nodes, i.e. a line or bus, not a star, ring, or multiply connected network. The number
of devices that can be connected to a single line is defined in the RS-485 standard by the input impedance
of 32 UNIT LOADs. The wire and circuits interfacing on this 2 wire connection is considered the PHYSICAL
LAYER. (RS-485 is the same physical layer as used with BACNET MSTP.)
No provisions for biasing resistors or termination resistors are provided on the control. If required, this will
need to be provided externally.
The PVI gateway does provide optional biasing (default) and can provide a termination resistor, if required.
ITEMS REQUIRED FOR GATEWAY INTERFACE:
One or more water heaters with a TempTrac control (red/orange LED display with 6 tactile buttons)
including the RS-485 adapter.
Protonode Gateway with Power supply adapter (when ordering, please specify what protocol is required;
BACNET MSTP, BACNET IP, LONWORKS or MODBUS TCP).
Protonode Gateway Manual (Covers general information for the gateway).
PV7069-T.PDF Interface manual that covers specifics for interfacing with the TempTrac system. Also
includes the points list for the TempTrac control system. (This document).
120VAC power outlet for the power supply.
Computer with web browser and Ethernet connection capability to configure gateway.
ITEMS REQUIRED FOR MODBUS DIRECT INTERACE:
One or more water heaters with a TempTrac control (red/orange LED display with 6 tactile buttons)
including the RS-485 adapter.
PV7069-T.PDF Interface manual that covers specifics for interfacing with the TempTrac system. Also
includes the points list for the TempTrac control system. (This document).