Watts tekmar 294 - Central Heating Operation Details; Terminal Unit Defaults; Warm Weather Shut Down (WWSD)

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IOM-T-294 2205 © 2022 tekmar
Baseboard
A baseboard or convector terminal unit is made up of a heat-
ing element with fins on it. This type of terminal unit relies on
the natural convection of air across the heating element to
deliver heated air into the space. The amount of natural con-
vection is dependent on the supply water temperature to the
heating element and the room air temperature.
Radiator
A radiator terminal unit has a large heated surface that is
exposed to the room. A radiator provides heat to the room
through radiant heat transfer and natural convection.
Fancoil
A fancoil terminal unit or air handling unit (AHU) consisting of
a hydronic heating coil and either a fan or blower. Air is forced
across the coil at a constant velocity by the fan or blower and
is then delivered into the building space.
Terminal Unit Defaults
When a terminal unit is selected the control loads default val-
ues for the boiler design, boiler maximum supply, and boiler
minimum supply temperatures. The factory defaults can be
changed to better match the installed system. Locate the
Terminal Unit setting in the Central Heating menu.
TERMINAL UNIT BOILER DESIGN BOILER MAX *BOILER MIN
Radiant Floor 120°F (49.0°C) 140°F (60.0°C) 140°F (60.0°C)
Baseboard 180°F (82.0°C) 200°F (93.5°C) 140°F (60.0°C)
Radiator 160°F (71.0°C) 180°F (82.0°C) 140°F (60.0°C)
Fancoil 190°F (88.0°C) 210°F (99.0°C) 140°F (60.0°C)
The Boiler Minimum is not applied when the boiler is
assigned to the Condensing boiler group.
Warm Weather Shut Down (WWSD)
When the outdoor air temperature exceeds the Warm Weather
Shut Down (WWSD) setting by 1°F (0.5°C), the central heat-
ing call is disabled and the central heating system is auto-
matically shut off. When the outdoor air temperature falls 1°F
(0.5°C) below the WWSD the central heating call resumes and
the heating system automatically turns on.
When the programmable schedule is on, the Room tempera-
ture unoccupied and the WWSD Unoccupied allow the central
heating system to operate at a lower boiler target and result in
additional energy savings.