Manual

© 2009 D 374 - 03/09 4 of 36
Section A
General
Operation
Page 4 - 6
Section B
Boiler
Reset
Page 6 - 9
Section C
DHW
Operation
Page 10 - 12
Sequence of Operation
Section A: General Operation
POWERING UP THE CONTROL
When the 374 control is powered up, all segments in the LCD are turned on for 2 seconds. Next, the control displays the control
type number in the LCD for 2 seconds. Next, the software version is displayed for 2 seconds. Finally, the control enters into the
normal operating mode.
TYPES OF DEMANDS
The control can control the supply water temperatures of two mix temperature systems and the boiler supply water temperature.
The type of demand the control receives determines the operation of the control.
Boiler Demand
When a boiler demand signal from the heating system is present, the control operates the boiler(s) to maintain the boiler supply
temperature based on the outdoor air temperature and the Boiler Characterized Heating Curve settings. Refer to section B.
DHW Demand
When a DHW demand is present, the control operates the boiler(s) to maintain the supply water temperature at least as hot as
the DHW exchange setting. Refer to section C.
Setpoint Demand
When a setpoint demand signal is present, the control operates the boiler(s) to maintain the supply water temperature at least as
hot as the Setpoint setting. Refer to section D.
Mix 1 Demand
When a mix 1 demand signal from the heating system is present, the control operates the mixing 1 device and the boiler(s) to
maintain the mix 1 supply temperature based on the outdoor air temperature and the Mix 1 Characterized Heating Curve settings.
Refer to section E.
Mix 2 Demand
When a mix 2 demand signal from the heating system is present, the control operates the mixing 2 device and boiler(s) to
maintain the mix 2 supply temperature based on the outdoor air temperature and the Mix 2 Characterized Heating Curve settings
or the control can provide a setpoint temperature. Refer to section E.
CHARACTERIZED HEATING CURVE
The control varies the supply water temperature based on the outdoor air
temperature. The control takes into account the type of terminal unit that
the system is using. Since different types of terminal units transfer heat
to a space using different proportions of radiation, natural convection
and forced convection, the supply water temperature must be controlled
differently. Once a terminal unit is selected, the control varies the supply
water temperature according to the type of terminal unit. This improves
the control of the air temperature in the building.
TERMINAL UNITS
The control provides for a selection between six different terminal unit types: two types of radiant floor heat, fancoil, fin-tube
convector, radiator and baseboard. When a terminal unit is selected, the control automatically loads the design supply temperature,
maximum supply temperature, and minimum supply temperature. See section B for Boiler Terminal Units and section E for Mixing
Terminal Units.
High Mass Radiant (1)
This type of a hydronic radiant floor is embedded in either a thick concrete or gypsum
pour. This heating system has a large thermal mass and is slow acting.
Decreasing Outdoor Temperature
Increasing Water Temperature
Terminal UnitTerminal Unit
Indoor DesignIndoor Design Outdoor DesignOutdoor Design
Design SupplyDesign Supply
Section D
Setpoint
Operation
Page 12
Section E
Mixing
Operation
Page 13 - 15