Operating instructions
35
• Argus Link (Multiple boiler applications only)
• Outdoor Sensor, if used.
A.  Provided with boiler.
B.  Locate outdoor sensor to protect against wind and 
direct sunlight. Mounting instructions provided with 
sensor. 
C.  Maximum wire length is 100 ft (30m) for 22 ga. 
wire, or 150 ft (45m) for 18 ga. wire.
D.  Connect wires to OUTDOOR SENSOR terminals. 
Wires are interchangeable.
• System Sensor (Multiple boiler applications only)
• Domestic Hot Water (DHW) Thermostat, if used.
A.  Use temperature control with dry contacts rated 
at 0.5 amps @ 120 VAC. Boiler control does not 
provide power to DHW temperature control. 
NOTICE
IMPORTANT: Do not apply power to DHW T-T 
terminals. Dry contact only, use of isolation relay 
may be necessary.
B.  Maximum wire length is 330 ft (100m) 22 gauge 
wire.
C.  Connect wires (interchangeable) to DHW T-T 
terminals. Wires are interchangeable.
• Central Heating Thermostat
A.  Use thermostat or boiler system control with dry 
contacts related 0.5 amps @ 120 VAC. Boiler 
control does not provide 24 VAC power to central 
heating thermostat.
B.  Locate and install thermostat per manufacturer's 
instructions. Maximum wire length is 330 ft (100m) 
for 22 ga. wire.
C.  Connect wires to CH T-T terminals. Wires are 
interchangeable.
FIGURE 8-4 External Connections 
(Do not apply external voltage to external terminals.)
NOTICE
Use dry contact for wires to CH T-T terminal and 
DHW T-T terminal. E33 error code is displayed if 
voltage is sent back to the control board. If error 
is not corrected for extended period of time, this 
voltage can permanently damage control board.
FIGURE 8-3  Isolation Relays for CH System Pump 
and DHW Pump
8 - ELECTRICAL CONNECTIONS
MBH CH PUMP DHW PUMP NOTE
50 
75 
100
1 A 1 A
Powered by 
Control Board
150 
200 
299
10 A 10 A
Powered by 
installed 10 Amp 
relay
If CH or DHW pump current is more than the maximum 
allowable current draw install proper eld sourced relays 
as shown in gure 8-3.
DHW 
Pump
CH 
Pump
CH 
Pump 
Relay 
120VAC 
coil
DHW 
Pump 
Relay 
120VAC 
coil










