Application

Application Notes
Sequence of Operation – Summary
28
Siemens Industry, Inc.
Application Note
A6V11692055
Smart Infrastructure – Building Products
2019-04-01
Dual Duct VAV Box Sequence with 2-Stage E-heat
a)
Cooling – When the room temperature [RM TEMP EVAL] rises above the effective cooling
setpoint [CLG STPT EFF], the chilled radiant ceiling device is activated and the cold duct
supply damper modulates from the cooling or vent flow minimum (whichever is larger) to the
cooling flow max to satisfy CLG STPT EFF.
b)
Heating – When the room temperature is below the effective heating setpoint [HTG STPT
EFF], the hot duct supply damper and 2-stage electric heat coils are controlled as follows:
⚫ Electric radiator activates.
⚫ The hot duct supply damper modulates to the larger of heating flow min or ventilation
min as 1
st
stage E-heat activates. (Supply damper airflow interlock is used to enable
electric heating coil operation.)
⚫ If the effective heating setpoint cannot be maintained, 2
nd
stage E-heat activates.
⚫ If the effective heating setpoint cannot be maintained using the minimum flow level, the
supply damper will modulate to heating flow max as required to satisfy HTG STPT EFF.
c)
Ventilation in deadband (configurable) – When the room temperature is between the effective
heating and cooling setpoints, the assigned ventilation supply damper is positioned at the
ventilation minimum flow setting.
d)
Warm-up cycle (via central command) – Radiator activates, the assigned heating duct supply
damper is positioned at heating flow max and the 2-stage E-heat coils are activated to satisfy
the effective heating setpoint.
e)
Cool down cycle (via central command) – The chilled radiant ceiling device is activated and
the assigned cooling duct supply damper is positioned at cooling flow max and the heating
coil(s) are closed / turned off to satisfy the effective cooling setpoint.
Room GreenLeaf
The GreenLeaf symbol on the room operator unit indicates that the room is
operating in an energy-efficient manner (symbol glows green). A user-entered
setpoint change to a non energy-efficient state will result in the leaf symbol turning
red.
⚫ Occupant can restore the room to energy efficiency by pressing the GreenLeaf
button (direct press on leaf symbol). Pressing the GreenLeaf button when it is
red removes the manual setpoint shift and restores the room to energy
efficiency (symbol glows green).
⚫ Setpoint shift tolerance before leaf symbol turns red is 4°F (2C), configurable.
⚫ GreenLeaf status can be externally reset to green (e.g. schedule change). The
behavior is configurable.
Central plant coordination
Collect demand from VAV supply air terminal boxes
The central plant collects and evaluates VAV supply airflow information to
coordinate primary air demand requests from the terminal boxes with central AHU
supply capacity.
Collect demand from room hot water valves (e.g., hot water radiators and
heating coils)
The central plant collects and evaluates hot water demand requests for the primary
hot water plant. In addition, central plant coordination provides for the following:
⚫ Operates the hot water system responsive to room operating modes;
⚫ Kick function (stroke the valves periodically to prevent sticking);
⚫ Disable hot water consumers in hot weather;
⚫ Permits valve position override for balancing or commissioning.
– END OF SEQUENCE OF OPERATION SUMMARY –