Application

Application Notes
Sequence of Operation – Summary
28
Siemens Industry, Inc.
Application Note
A6V11692053
Smart Infrastructure – Building Products
2019-04-01
Dual Duct VAV Box Sequence with Modulating Heat
a)
Cooling – When the room temperature [RM TEMP EVAL] rises above the effective cooling
setpoint [CLG STPT EFF], 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 heating coil (modulating electric 14069 and 14169;
modulating hot water 14369) are controlled as follows:
⚫ Radiator modulates.
⚫ Heating coil activates/modulates and VAV hot duct supply damper modulates to the
larger of heating flow min or ventilation min. (For application 14069 and 14169, supply
damper airflow interlock is used to enable electric heating coil operation.)
⚫ 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 heat coil is activates/modulates to satisfy
the effective heating setpoint.
e)
Cool down cycle (via central command) – 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 –