84
Call 1-
800-347-9575
for Technical Support
9.3.10 Boiler Control Testing / Wiring
Troubleshooting
Tools Required:
Flat blade screwdriver, nut driver, volt meter.
Controller Function:
Low Water Cut-Off Controller: Will shut off power
to the burner in the case that the water level in the
vessel is too low.
High Temperature Limit Controller: Will shut off
power to the burner in the case that the water
temperature exceeds the limit set on the
controller.
Triple Aquastat Temperature Controller: Operates
the burner and circulation pump based on a call
for heat and the low limit setting (minimum
temperature maintained in the vessel).
Note:
During this test, if the Controllers do not function
as stated, call Technical Services for assistance, or
Customer Service to order a service part.
During a portion of this test, high
voltage electrical components will be energized.
Only a certified electrician is to perform the
following procedures, and with extreme caution.
Procedure:
1. Make sure that the Low Water Cut-Off Control
and High Temperature Limit Aquastat reset
buttons are reset (pushed in).
2. Make sure that there is not a call for heat, and
allow the boiler to cool to a temperature below the
Triple Aquastat Temperature Control high setting.
3. Check for 115 volts across the white and black
terminals on the terminal strip in the terminal box.
a. If voltage is present, check the preheater
connection in the burner wiring box. If there
is not 115 volts at the preheater, check the
following wiring on the Triple Aquastat
Temperature Control:
i. Make sure that L1 has black wire
from low water cut-off control.
ii. Make sure that B1 has black wire
from vessel wiring box.
iii. Make sure that L2 has white wire
from low water cut-off.
iv. Make sure that B2 has white wire
Limit
Aquastat
Gnd
GND
Power Supply
White
Black
Green
1
3 4 5
2
T
T
L1
L2
C1
B1
RED
Terminal Box Cover
13 14
15 16
Hour Meter
Fuel Pump
Circulator
Pump
Terminal
Box
BLK
WHT
ORG
ITT McDonnell Model
750P-MT-120
Low Water Cutoff
Triple
Aquastat
B2
C2