12
Reset Ratio
The controller uses the following four settings to calcu-
late the Reset Ration (RR):
For example, using the Mode 5 default values, the RR
would be .56:1.
Heater Start (BOIL START)
The BOIL START temperature is the theoretical supply
water temperature that the system requires when the
outdoor air temperature equals the OUTDR START
temperature setting. The BOIL START is typically set
to the desired building temperature.
Outdoor Start (OUTDR START)
The OUTDR START temperature is the outdoor air
temperature at which the Controller provides the BOIL
START water temperature to the system. The OUTDR
START is typically set to the desired building tempera-
ture.
Outdoor Design (OUTDR DSGN)
The OUTDR DSGN is the outdoor air temperature that
is the typical coldest temperature of the year where the
building is located. This temperature is used when
doing heat loss calculations for the building.
135°F
Decreasing Outdoor Temperature
70°F
-10°F
180°F
Fig. 19: Heater Start
Heater Design (BOIL DSGN)
The BOIL DSGN is the water temperature required to
heat the zones when the outdoor air is as cold as the
OUTDR DSGN temperature.
Warm Weather Shut Down (WWSD)
When the outdoor air temperature rises above the
WWSD setting, the Controller turns on the
WWSD
segment in the display. When the Controller is in Warm
Weather Shut Down, the
Dem 1
segment is displayed
if there is a heat demand. However, the Controller
does not operate the heating system to satisfy this
demand.
External Temperature Target
Input
When Mode 7 is selected, the controller allows for an
external control to operate the heater temperature
through an input signal generated by a Building
Management System (BMS) or Energy Management
System (EMS).
CFH
A CFH is generated when a contact closure is present
at the enable/disable connection on P1 pins 1 and 2
(or pins 1 and 3 for Indirect DHW), and an analog pos-
itive 0-10 VDC signal is applied to the +V (in) input
(terminal 10). The negative V (DC) is applied to the
Com/- input (terminal 9).
0-10 VDC or 0-20mA External Input
(Mode 7)
When the 0-10VDC range is selected, an input voltage
of 1VDC corresponds to a heater target temperature of
50ºF (10ºC). An input voltage of 10VDC corresponds
to a heater target temperature of 210ºF (99ºC). As the
voltage varies linearly between 1VDC and 10 VDC,
the heater target temperature varies linearly between
50ºF (10ºC) and 210ºF (99ºC). If a voltage below
0.5VDC is received, the heater target temperature is
displayed as “ - - -“ indicating that there is no longer an
internal CFH.
A 0-20 mA signal can be converted to a 0-10VDC sig-
nal by installing a 500 Ohm resistor in parallel to the
input signal on the controller’s terminals (terminals 9 &
10). See Fig. 13 on page 7.
RESET RATIO (RR) =
BOILER DESIGN — BOILER START
OUTDOOR START — OUTDOOR DESIGN
