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Table 9. Boiler Target Temperature
Reset Ratio
Outdoor T
emperature
8.C.4
Thermal Boost Function
8.C.4.a
Outdoor Reset
To ensure that the heating system always satisfies a call for
heat, the control is equipped with a thermal boost feature.
If in Outdoor Reset Mode, the control will have a fixed 30
minute Thermal Boost Interval.
To set the desired warm weather shutdown
temperature: Press and hold the Mode button and
simultaneously adjust the ECONOMY dial to the
desired temperature setting.
To turn warm weather shutdown of
f - which will allow
space heating regardless of outdoor temperature -
press and hold the Mode button and simultaneously
turn the ECONOMY dial fully counter-clockwise.
Release the Mode button. After doing this, be sure
to reset the ECONOMY dial to the correct setting.
Any time the outdoor temp exceeds the WWSD
setpoint, the display will toggle boiler temperature (8
seconds, outdoor temperature (2 seconds) and OFF
(2 seconds). Boiler will not fire for a call for heat
until the outside temperature drops below the
WWSD setpoint.
8.C.3 Adjusting Outdoor Reset
Ratio
The outdoor reset will regulate the boiler’s
temperature based on the temperature
outside. On cold days, the boiler will run at
higher temperatures to meet the heating
load in the house. On warmer days, the
boiler will run at lower temperatures to save
energy while still meeting the heating needs
of the house.
The Outdoor Reset uses a reset ratio
method to control the boiler temperature.
The reset ratio determines how much the
boiler temperature is adjusted for changes
in outdoor temperature. A reset ratio of
2.0 means that for each 1 degree drop in
outdoor temperature, the boiler temperature
will increase 2 degrees. See Table 9.
Outdoor Reset has a boost function based
on a 30 minute time interval using a 10
degree temperature boost. You can check
the current target temperature at any time,
by pressing the Mode button in four short
intervals.
To set the desired outdoor Reset Ratio
1. Locate the Outdoor Design Temperature
on the left side of the chart (the coldest
outdoor temperature at design load
conditions).
2. Locate the Boiler Target Temperature
(the required supply water temperature
at design load conditions) across from
the Outdoor Design Temperature.
3. Follow the column up to the top of the
chart to obtain the Reset Ratio setting.
4. Adjust the ECONOMY dial on the control
to that Reset Ratio.
LAARS Heating Systems
