51
P/N HN-IOM-1 82-0331 Copyright 2009 Mestek, Inc.
Finned copper tube gas boilers & water heaters – Control manual
Troubleshooting
(continued)
9
Table 11
Status screen fault displays
(continued)
FAULT EVENT &
INTERLOCK
TERMINALS
CAUSE/Discussion
DISPLAY
Action required to
reset from fault
LOW WATER CUTOFF
(J1, LWCO)
Occurs on opening of a low water cutoff switch connected
to J11 LWCO terminals. The boiler is shut down until the
fault is corrected.
The display continues showing the SUPPLY, HEADER or
other temperature, whichever had been selected for display.
The temperature shown is the value detected at the sensor
listed.
FAULT SUPPLY
LOW WATER CUTOFF
168°F
Automatically
resets control after
temperature drops
OPEN ____ SENSOR
(ANY SENSOR)
Occurs when the HeatNet control detects an open circuit
on any sensor that should be in operation. The boiler
will shut down on the failure of any sensor except the
OUTDOOR sensor. If the OUTDOOR circuit is open,
and the boiler is set for outdoor reset operation, the control
reverts to fixed setpoint operation, controlling to either
the LOCAL or SYSTEM setpoint, until the condition is
corrected.
The display continues showing the SUPPLY, HEADER or
other temperature, whichever had been selected for display.
The temperature shown is the value detected at the sensor
listed.
FAULT SUPPLY
OPEN ________ SENSOR
168°F
(The name of the sensor
appears where the _____
is above)
Automatically resets
control after external
limit closes
SHORTED ____ SENSOR
(ANY SENSOR)
Occurs when the HeatNet control detects a short circuit on
any sensor that should be in operation. The boiler will shut
down on the failure of any sensor except the OUTDOOR
sensor. If the OUTDOOR circuit is open, and the boiler is
set for outdoor reset operation, the control reverts to fixed
setpoint operation, controlling to either the LOCAL or
SYSTEM setpoint, until the condition is corrected.
The display continues showing the SUPPLY, HEADER or
other temperature, whichever had been selected for display.
The temperature shown is the value detected at the sensor
listed.
FAULT SUPPLY
SHORTED _____ SENSOR
168°F
(The name of the sensor
appears where the _____
is above)
Automatically resets
control after external
limit closes
VAR FREQ DRIVE
(J11A, VFD)
Occurs when the variable frequency drive sends a fault
signal to the HeatNet control VFD terminals on J11A.
The display continues showing the SUPPLY, HEADER or
other temperature, whichever had been selected for display.
The temperature shown is the value detected at the sensor
listed.
FAULT SUPPLY
VAR FREQ DRIVE
168°F
Automatically
resets control after
temperature drops
