Honeywell SV2 Series User Manual page 48

SV2 Series Safety Shut-off Valves
Reference documents:
• 32-00018, SV2 Series Valves Installation Instructions
• 32-00030, HMI Tool Installation Instructions
• 32-00031, HMI / PC Tool User Manual
• 32-00037, PC Tool Installation Instructions
Valve Modbus Bias Setup
The SV2 Series valve can communicate via Modbus RTU communication with any compatible device. Only RTU communications
with 1 start bit, 8 data bits, 1 stop bit and no parity is supported.
When more than one SV2 Series valve is connected to the HMI or PC Tools or directly connected to a building automation
system, the Modbus termination and bias resistors should be adjusted appropriately. The resistors can be found inside the
electrical enclosure on the right-hand side. Refer to
valves models; valves where the 9th digit in the part number string are 6. Reference
The TERMIN. (termination) resistor in the ON position helps to improve signal integrity for the best performance in regards to
EMC (electromagnetic compatibility). The termination resistor may be especially helpful to improve communication when the
SV2 Series connected valve is at the end of the communication BUS.
The BIAS resistors in the ON position provide differential resistance for some older communication systems where
communication can be lost with zero voltage present on the BUS. Resistors 1 and 3 should always be in the OFF or ON positions
together. Refer to Table 9 below.
NOTES:
• If communication is problematic with all daisy-chained valves connected to the master control,
adjusting the two BIAS resistors may solve the issue.
• When replacing the valve front electrical enclosure, the tightening torque for each fastener
should be between 1.26 and 1.54 Nm (11 to 13.63 in-lbf).
Table 9. Modbus bias resistor setup.
Table 9 below. Termination and bias resistors are present in all intelligent
SV2 Series Valve Differential Biasing
Not at At BUS Not
BUS end end required
X
X
X
X
48
Fig. 1 for valve nomenclature details.
Required
BIAS
X
TERMIN.
BIAS
BIAS
X
TERMIN.
BIAS
BIAS
X
TERMIN.
BIAS
BIAS
X
TERMIN.
BIAS
OFF ON
X
1
X
2
X
3
X 1
X 2
X
3
X
1
X
2
X
3
X 1
X 2
X
3
32-00029—02