Lochinvar SYNC 1.5 - Manual (Page 9)

9
Modbus Instructions
4
Wiring Requirements
RS-485 Communication Bus
• Maximum Length = 4000 feet
• Cable Specifi cation = 24 AWG / A,B (twisted pair) and GND Shielded, with characteristic Impedance = 120 ohm
• Maximum Load = 32 units (32 nodes)
NOTE: Cable must be terminated with 120 ohm impedance matching resistor on each end.
Note that when the System Supply Temperature and/or the Tank Temperature are provided by the BAS, they need to be refreshed
every few seconds. This is required in order to prevent unwanted fl uctuations in these temperatures. If these values are not
provided every few seconds (timeout is programmable), the boiler will revert to its own internal control. If neither of these
temperatures is provided by the BAS, but any of the other control signals are being provided, the BAS will still need to refresh
these inputs at least every 4 minutes.
Physical Wiring
Figure 4-1_Terminal Strip Connections
1
ALARM
LBL20052 RE
V B
30 SHIELD GND
MOD BUS
0 -
10V
INP
U T
2
C
O
N
TA
CT
S
3
RUN
T
IME
4
CO
N
TA
CT
S
5
LO
UVER
6
PROV
ING
8
FL
O
W
SW
IT
CH
10 FL
OW SW
IT
CH
29 A 26 SEN
SOR
25 T
ANK
24 SEN
SOR
23 O
UT
DOOR
22 SENSOR 21
SY
STE
M
20
(-)
19
(+
)
18
SHIELD GND
17 B 16 A 15 SHIELD GND 14 W 13 R 11
TA
NK
12 THERMOST
AT
28 B 27 S
H
IELD GND
CASCADE
ENABLE
A B
A B
A B
BU
IL
D
ING
MA
N
AGEM
EN
T
SY
STEM
LOUVER PROVIN
G
SWIT
CH
TANK THER
MOST
AT
ENABLING DEVICE
SY
STEM S
EN
SOR
OUTDOOR SE
N
SOR
TANK S
EN
SOR
SHIEL
D
SHIEL
D
FRO
M
PRE
VIOUS BOILER
TO
NEX
T BOILER
SHIEL
D
HEA
T
EX
CHANGER 2
FL
OW SWIT
CH
HEA
T
EX
CHANGER 1
FL
OW SWIT
CH
A B
SHIEL
D
MODB
U
S
COM
M
U
N
IC
A
TION BU
S
TO
NE
XT
BOILER
9
HEX 1
7
H
EX
2