© 2010 D 265 - 07/10
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Self Adjusting
Water Temperature
Boil Target
(Occupied)
Boost
Boil Target
(UnOccupied)
Boost setting - 20 minutes to 8 hours
Time
Fancoil (3)
A fancoil terminal unit or Air Handling Unit (AHU) consists 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.
Fin-Tube Convector (4)
A convector terminal unit is made up of a heating 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 convection to the space is dependant
on the supply water temperature to the heating element and the room air temperature.
Radiator (5)
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.
Baseboard (6)
A baseboard terminal unit is similar to a radiator, but has a low profile and is installed at
the base of the wall. The proportion of heat transferred by radiation from a baseboard is
greater than that from a fin-tube convector.
WARM WEATHER SHUT DOWN (OCC and UNOCC)
The Warm Weather Shut Down (
WWSD
) disables the space heating system during warm outdoor weather. There is a separate WWSD
for both the occupied and the unoccupied periods. When the outdoor air temperature rises above the WWSD setting, the control turns
on the
WWSD
pointer in the display. When the control is in WWSD, the
Boiler Demand
pointer is displayed if there is a boiler demand.
However, the control does not operate the heating system to satisfy this demand. The control does respond to a DHW demand or a
setpoint demand and operates as described in sections D and E. WWSD is not active when using an external input signal.
BOOST
When the control changes from the unoccupied mode to the occupied mode,
it enters into a boosting mode. In this mode, the supply water temperature to
the system is raised above its normal values for a period of time to provide a
faster recovery from the setback temperature of the building. The maximum
length of the boost is selected using the
BST
setting.
Typical settings for the boost function vary between 30 minutes and
two hours for buildings that have a fast responding heating system. For
buildings that have a slow responding heating system, a setting between
four hours and eight hours is typical. After a boost time is selected, the
setback timer must be adjusted to come out of setback some time in
advance of the desired occupied time. This time in advance is normally
the same as the
BST
setting.
If the building is not up to temperature at the correct time, the
BST
setting should be lengthened and the setback timer should be
adjusted accordingly. If the building is up to temperature before the required time, the
BST
setting should be shortened and the setback
timer should be adjusted accordingly. If the system is operating near its design conditions or if the supply water temperatures are being
limited by settings made in the control, the time required to bring the building up to temperature may be longer than expected.
