Lochinvar FTxl 500 Service Manual page 24

1
Service
Figure 1-1 Outdoor Air Reset Curve
SET POINT AT
LOW OUTDOOR
TEMPERATURE
(SH)
SET POINT
SET POINT AT
HIGH OUTDOOR
TEMPERATURE
Set Point (1 - 3) at Low Outdoor Temperature
When the outdoor air temperature drops to the Outdoor
(1 - 3) Low parameters, the calculated set point will be at
this setting (FIG. 1-1). If the outdoor air temperature
drops further, the set point will continue to increase above
this setting. However, if SH1, SH2, and SH3 are set lower,
the water temperature will be limited by these set points
instead. These parameters can be changed by the installer
by accessing the Set point 1 at Low Outdoor Temp 1, Set
point 2 at Low Outdoor Temp 2 and Set point 3 at Low
Outdoor Temp 3 parameters. The temperature range of
this parameter is 68°F (20°C) to 190°F (88°C). The default
value is 180°C (82°C).
Set Point (1 - 3) at High Outdoor Temperature
When the outdoor air temperature rises to or above
Outdoor (1 - 3) High parameters, the calculated set point
will be at this setting (FIG. 1-1). These parameters can
be changed by the installer by accessing the Set point 1 at
High Outdoor Temp 1, Set point 2 at High Outdoor Temp
2 and Set point 3 at High Outdoor Temp 3 parameters. The
temperature range of this parameter is 68°F (20°C) to 190°F
(88°C). The default value is 70°F (21°C).
24
HIGH OUTDOOR
TEMPERATURE
LOW OUTDOOR
TEMPERATURE
Outdoor Air Shutdown (SH1 - SH3)
When the outdoor temperature rises above this point, the
control will block the corresponding SH demand (DHW
demands will still be active). These parameters can be changed
by the installer by accessing the Outdoor Air Shutdown SH1,
SH2, and SH3 parameters. The temperature range of this
parameter is 32°F (0°C) to 104°F (40°C). The default value is
70°F (21°C).
Outdoor Air Shutdown Differential (SH1 - SH3)
The outdoor air shutdown differential parameter is the number
of degrees below Outdoor Air Shutdown SH1, SH2, and SH3
parameters the outdoor air temperature must go before the
boiler will respond to the corresponding SH demand. These
parameters can be changed by the installer by accessing
the Outdoor Air Shutdown Differential SH1, SH2, and SH3
parameters The temperature range of this parameter is 0°F
(0°C) to 54°F (30°C). The default value is 10°F (6°C).
Shift Reset Curve (SH1 - SH3)
There is a shift reset parameter for each outdoor reset curve.
The shift reset parameter shifts the actual set point above
or below the calculated set point by the number of degrees
in this parameter. These parameters can be changed by the
installer by accessing the Shift Reset Curve SH1, SH2, and SH3
parameters. The temperature range of this parameter is -18°F
(-10°C) to 18°F (10°C). The default value is 0°F (0°C). This
feature will be active if this parameter is set to anything other
than 0°F (0°C).
Service Manual