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Raypak

Raypak Protege VSP Pumps

Raypak publishes more of this interface than any other manufacturer here: protocol, baud rate, slave address, function codes, cable type and length are all in the manual. It makes the Protege the least ambiguous pump on the pad to integrate.

The published specification

ItemValue
ProtocolModbus RTU
Max baud rate9600 bps
Selectable baud rates1200, 2400, 4800, 9600
Function codes0x03, 0x04, 0x06, 0x16
Slave address range1 to 247, default 2
BusIsolated A/B, no 120 ohm terminating resistor fitted
ConnectorSP1310, four pin
Straight from Raypak's manual. Note the default slave address is 2, not 1 — unusual, and easy to get wrong by assumption.

Wiring the SP1310 connector

The RS-485 socket is on the side of the variable-speed drive. Raypak supplies the connector but not a cable, so you make the lead up yourself. Pin numbers are moulded into the base of the terminals.

PinFunctioniSmart Module
1APORT terminal A
2BPORT terminal B
4Ground and 120 ohm termination, long runs onlySee below
The SP1310 four-pin connector with pin 1 as A, pin 2 as B, and pin 4 available for ground and a 120 ohm terminating resistor on long runs.
Two pins for a short run. Pin 4 earns its place only when the run gets long.
  1. 1

    Disassemble the female connector

    Pin numbers are on the base of the terminals — check them rather than counting.

  2. 2

    Prepare the cable

    Raypak specifies 2-wire 22 AWG unshielded twisted pair, up to 100 m (109 yards) between pump and controller.

  3. 3

    Solder pin 1 to A and pin 2 to B

    Then reassemble the connector and plug it into the RS-485 socket on the pump.

  4. 4

    Set the baud rate at the pump

    Use the pump's baud rate menu to pick 1200, 2400, 4800 or 9600, then press MODE to save. It must match what the module is configured for.

When it does not respond

SymptomWhere to look first
No communication at allBaud rate mismatch, then the slave address — remember the default is 2.
Still nothingSwap A and B, then confirm the connector is in the RS-485 socket and not an adjacent one.
Works close, fails on a long runMissing termination. Bring pin 4 in with ground and a 120 ohm resistor.
IntermittentRun exceeds 100 m, or the pair is not twisted.

Sources