46
Reset Ratio Settings
The controller uses the four following settings to determine
the reset ratio:
1.
Heater Start (
Boil START
)
The Boil START temperature is the theoretical heater
supply water temperature that the heating system
requires when the outdoor air temperature equals the
OUT START temperature setting. The Boil START is
typically set to the desired building temperature.
2.
Outdoor Start (
OUT START
)
The OUT START temperature is the outdoor
temperature at which the control provides the
Boil START water temperature to the system. The
OUT START is typically set to the desired building
temperature.
3.
Outdoor Design (
OUT DESIGN
)
The OUT START is the outdoor temperature that is
typical coldest annual temperature where the building
is located. This temperature is used when completing
heat loss calculation for the building.
4.
Heater Design (
Boil DESIGN
)
The Boil DESIGN temperature is the water temperature
required to heat the heater zones when the outdoor
air is as cold as the OUT DESIGN temperature.
Warm Weather Shut Down (WWSD)
When the outdoor air temperature rises above the WWSD
setting, the control turns on the WWSD segment in the
display. When the control is in the Warm Weather Shut
Down, the Dem 1 segment is displayed if there is a heat
demand. However, the control does not operate the heater
to satisfy this demand. The control continues to respond
to DHW demands.
Reset Ratio
The controller uses the following four settings to calculate
the Reset Ratio (RR):
For example, when using the default values, the RR is:
RESET RATIO =
(OUTDOOR START – OUTDOOR DESIGN)
(BOILER DESIGN – BOILER START)
RR = (70 - 10) / (180 - 70) = 0.55
Therefore, the RR is 0.55:1 (Outdoor : Water).
RR=(70 - 10) / (180-70) = 0.55
Therefore, the RR is 0.55:1 (Outdoor : Water).
Decreasing Outdoor Temperature
Inc
reasing
W
at
er
Temperatu
re
Boil
START
OUT
DESIGN
Boil DESIGN
START
OUT
Figure 54. Reset Ratio
NOTE:
The wiring diagrams in this manual show all
standard options. Refer to the large wiring diagram
provided with your heater for options installed on your
specific unit(s).
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