5
FREEZE PROTECTION
Do not install the boiler in a room likely to freeze.
NOTE: The following integral feature of the boiler control pro
-
vides some protection for the boiler only, not for the system.
The control module provides freeze-up protection as follows
when the boiler water temperature drops below 45° F:
Below 45° F, the boiler circulator operates constantly.
•
Below 37° F, the boiler turns on at low fire.
•
Boiler and circulator turn off if boiler water temperature
•
rises above 50° F.
This feature of the boiler control does not eliminate the
possibility of freezing. The installation must still use rec
-
ognized design, installation and maintenance practice to
prevent freeze potential for the boiler and system.
CAUTION
!
SUPPLY TEMPERATURE BOOST
In outdoor reset operation (factory supplied, field installed
outdoor sensor connected), the boiler control automatically
increases the target outlet water temperature if a call for heat
exceeds 10 minutes. At each 10 minutes of a continuous call
for heat, the control module increases the target temperature
by 18°F. The module will continue increasing target tempera
-
ture until it reaches the value set in Parameter 4.
When the call for heat ends while target temperature is
“boosted,” the target temperature drops about 2°F for each
minute the thermostat is open.
Purpose of “boosting”
: If the target temperature happens
to be too low, the control “boosts” the target temperature until
the supply water meets the system’s needs.
OUTDOOR RESET OPERATION (IF USED)
Target temperature with outdoor reset:
All boilers are
shipped with an outdoor temperature sensor. When this sen
-
sor is installed (low voltage terminal strip terminals A1 and
A2), the boiler control regulates target outlet water temper
-
ature based on outside temperature. Set the temperature
curve by setting Parameter 4 to:
ODT (outdoor design temperature for the area).
•
For ODT of 0°F or lower, set Parameter 4 to the desired
•
supply temperature at the ODT.
For ODT above 0°F, set Parameter 4 to the desired sys
-
•
tem temperature when outdoor temperature is 0°F.
Target Outlet T
emperature, °F
Outside Temperature, °F
Outdoor Reset Target Temperature
210
50
70
60
50
40
30
20
10
0
-10
-20
70
90
110
130
150
170
160
190
120
Parameter 4 = 190°F
Parameter 4 = 150°F
Parameter 4 = 170°F
Reset Curve Calculations
Reset cuRve:
The graph below shows how the boiler con
-
trol calculates target temperature.
For outdoor temperature at or below 0°F, the target tem
-
•
perature equals Parameter 4 and never higher.
For outdoor temperature above 0°F, the target tempera
-
•
ture is reduced on a curve that would result in 60°F supply
temperature at 70°F outdoor temperature.
Summer/winter switch option: Install a summer/winter switch, if
desired, to disable the boiler (space heating) circulator during
non-heating months. Connect switch across the outdoor sensor
terminals. When switch closes, the boiler circulator is disabled
and the boiler operates only on call for DHW heating.
Target Outlet T
emperature, °F
Outside Temperature, °F
Default Reset Curve
Outdoor Reset Target Temperature
210
50
70
60
50
40
30
20
10
0
-10
-20
70
90
110
130
150
170
160
190
180
120
Parameter 7 = 60°F
Parameter 4 = 180°F
Parameter 6 = 0°F
II - OPERATING INFORMATION
