37
P/N HN-IOM-1 82-0331 Copyright 2009 Mestek, Inc.
Finned copper tube gas boilers & water heaters – Control manual
Menu item
Under . . .
Explanation
WWS SETPOINT
OUTDOOR AIR
The boiler and its circulator shut down when the outside air temperature is above WWS
SETPOINT if outdoor air reset is enabled (ON). This requires an outdoor sensor when enabled.
The differential is 2°F; i.e., the boiler will shut off if the outdoor temperature is equal to
or greater than OUTDOOR AIR setting. The outdoor temperature must drop 2°F below
OUTDOOR AIR setting for the boiler to turn back on.
If the OA OVR input is closed, outdoor reset and warm weather shutdown are overridden. The
boiler will run at LOCAL/SYSTEM SETPOINT. This function can be used to operate the HeatNet
system at a fixed temperature (equal to the LOCAL SETPT or SYSTEM SETPT), for applications
such as DHW heating.
LOW WATER
AT
HIGH OA TEMP
HI WATER
AT
LOW OA TEMP
OUTDOOR AIR
SET OA SETPTS
These temperatures determine the reset curve
for supply water temperature. High water at
low outside air means the design water
temperature for maximum load (at ODT, or
outside design temperature for the
installation). The other end of the reset curve is
the low water temperature at high outside air
temperature. The low water temperature is
generally equal to room temperature, meaning
no heat input to the space would occur below
this outside air temperature.
POST PRG TIME
PUMP OPTIONS
SYSTEM PUMP
SYSTEM PUMP settings apply to a system pump if it is to be cycled by the HeatNet control.
Connect a relay or starter for the system pump to the SYSTEM PUMP terminals (J13). DO NOT
directly connect the pump motor with these terminals. They are for pilot duty only.
To prove system flow before boiler operation, install a flow proving switch across SYSTEM
WTR FLOW terminals (J11A). Place a jumper on these terminals if system flow proving is not
used.
POST PRG TIME keeps the pump running for the specified time after call for heat is
completed, allowing distribution of residual heat to the system.
WARNING — The system must be equipped with a bypass pressure regulator or other means
to prevent dead-heading if system valves close when call for heat is completed.
ALWAYS ENABLED
PUMP OPTIONS
SYSTEM PUMP
If enabled, the system pump remains on constantly. If pump is constant, DELTA TEMP and
POST PRG TIME have not effect.
NOTE: If the option is enabled, the system pump will shut down if outdoor air reset is
enabled and the outside temperature is above OA SETPOINT (summer mode operation).
WARNING — The system must be equipped with a bypass pressure regulator or other means
to prevent dead-heading if system valves close when call for heat is completed.
SUMMER PUMP JOG:
PUMP OPTIONS
SYSTEM PUMP
This option is available to prevent the pump from seizing during long idle periods. Enable
the option to have the system pump operated once per week (specify the day in setup). The
pump will cycle on at 12:00 AM on the day specified. It will operate for a time equal to the
time set for POST PRG TIME.
WARNING — The system must be equipped with a bypass pressure regulator or other means
to prevent dead-heading if system valves close when call for heat is completed or during
summer or outdoor air shutdown.
DELTA TEMP ENAB
PUMP OPTIONS
LOCAL PUMP
The boiler pump can be set to run after boiler shutdown to distribute residual heat to the
heating system. Delta enable causes the boiler pump to run until the temperature difference
between boiler inlet and outlet is less than DELTA TEMP (see below). The pump will continue
to run an additional period after this for the amount of time specified in PURGE TIME (below).
DELTA TEMP
PUMP OPTIONS
LOCAL PUMP
When DELTA ENABLE (above) is set to “ON,” the boiler pump will run until the temperature
difference across the boiler is less than DELTA TEMP. (The pump will run an additional time
equal to the PURGE TIME.) An inlet temperature sensor is required.
Table 9
Setup menus — parameter explanations (continued)
Control menus and adjustments
(continued)
7
