46
c. CH Modes: The CH modes allow the operator
to change the way the boiler operates to satisfy
central heating demands.
•
Mode 0, Indoor Thermostat
: This is the default
mode in which the boiler responds to a demand
from an indoor thermostat or zone control panel
at terminals #1 and #2 in the
P
ure
F
ire
®
control
panel. The control targets a fixed setpoint and
as the boiler water temperature approaches
the target, the control begins to reduce the fuel
input. This mode doesn’t require an outdoor
sensor.
•
Mode 1, Indoor Thermostat with Outdoor Reset
:
When operating in this mode, the control uses the
outdoor temperature and installer selected data
to calculate a target boiler water temperature. A
detailed description of outdoor reset is presented
later in this section.
•
Mode 2, Permanent Demand and Outdoor Reset
:
In this mode, the boiler operates to maintain a
supply (header) temperature calculated by the
outdoor reset algorithm.
The boiler operates independently of any room
thermostats. This is useful in buildings with many
zones which operate on independent thermostats
to prevent the boost function (described later in
this text) from increasing the target temperature
due to a long sustained call for central heat
resulting from overlapping individual calls.
•
Mode 3, Permanent Demand
: This mode
is similar to Full Outdoor Reset except that
the control targets a fixed setpoint instead of
a calculated setpoint based on the outdoor
temperature. Again, the boiler control operates
independently of input from room thermostats. If
a switch between terminals #1 and #2 is closed,
the target temperature will be set back by 18°F
(10°C).
•
Mode 4, 0 -10V Input to Modulate Setpoint
:
This allows the boiler supply target to be set
by an external analog 0-10 volt signal. The
input for this signal is at terminals #15 & #16.
A call for heat will be generated by a signal of
1.5 VDC or higher. The setpoint for an input
voltage between 1.5 and 2.0 VDC will result
in a boiler setpoint of 68°F (20°C). An input
voltage of 10 VDC will result in a setpoint of
195°F (91°F).
•
Setback
: If a switch is closed across terminals
#1 & #2, a setback of 18°F (10°C) is applied
to the calculated target temperature. This
feature is useful in a building (such as an office
building) that is unoccupied during certain
times. A switch or timer can be used to set
back the boiler target temperature during
unoccupied periods.
d. Pump Purge Time: The installer can define
the length of time that the circulators operate
after the end of call for heat. The CH and
General circulator post purge time can be set
independently. The following chart shows the
range and default values for both of these pumps.
e. Outdoor Reset: Since heating loads are typically
lower when the outdoor temperature rises,
outdoor reset lets the installer reduce the boiler
target temperature as the outdoor temperature
increases. As mentioned above, this increases the
efficiency of the boiler. This is especially true with
condensing boilers because it helps to recover the
heat from the water vapor which, in conventional
boilers, carries valuable energy out with the
exhaust.
f. System Type Presets: For convenience, the
P
ure
F
ire
®
boiler control provides preset values for
the outdoor reset parameters based on the system
type. Table 8.17 shows the values that are applied
when different system preset types are selected.
If the system type, “User Defined” is chosen the
outdoor reset definition values may be adjusted.
If changes are made to the boiler design or mild
weather boiler temperatures, the system type is
automatically switched to, “User Defined”.
BOILER CONTROL: OPERATION
Table 8.15: CH Modes
Mode
Display
Target
Temperature
Action when
Terminals #1 &
#2 Closed
0
Indoor
Thermostat
Fixed Setpoint
Call for Central
Heating
1
Indoor
Thermostat
with OD Reset
Outdoor Reset
Calculation
Call for Central
Heating
2
Permanent
Demand & OD
Reset
Outdoor Reset
Calculation
18°F (10°C)
Target Setback
3
Permanent
Demand
Fixed Setpoint
18°F (10°C)
Target Setback
4
0-10 V Input
to Modulate
Setpoint
External Analog
(0-10 VDC) Input
of Setpoint
No Effect
Managing Burner Only
Figure 8.32: CH Settings – CH Modes
Table 8.16: Pump Purge Time Ranges & Defaults
Figure 8.33: CH Settings – Pump Purge Time
Circulating Pump
Minimum
Default
Maximum
Central Heating (CH)
0
1 minute
60 minutes
General
0
1 minute
60 minutes
Managing Burner Only
Summary of Contents for PUREFIRE PFC-1000
Page 1: ...PUREFIRE Boilers PFC 850 PFC 1000 PFC 1500 Gas Installation Operation Maintenance Manual ...
Page 82: ...80 Figure 13 4 Control System REPAIR PARTS ...
Page 84: ...82 Figure 13 5 Condensate System REPAIR PARTS ...
Page 90: ...88 APPENDIX C USER MENU APPENDIX C USER MENU Figure C 1 User Menu Managing Burner ...
Page 91: ...89 APPENDIX C USER MENU Figure C 1 User Menu Dependent Burner ...
Page 92: ...90 APPENDIX D INSTALLER MENU STRUCTURE APPENDIX D INSTALLER MENU STRUCTURE ...
Page 93: ...91 APPENDIX D INSTALLER MENU STRUCTURE ...
Page 95: ...93 SERVICE LOG SERVICE LOG Date Serviced By Description of Service Serial Number ...
Page 96: ...94 NOTES ...
Page 97: ...95 NOTES ...