Appendix_C_Examples_of_Sequences_of_Operations,_Graphics_and_Points_Lists.pdf

Appendix C - Examples of Sequences of Operations, Graphics and Points Lists

RFP#: FA520919RA010

Project Name: EMCS System Install and DDC Controls

Appendix C Examples of Sequences of Operations, Graphics and Points Lists

Table of Contents

1.0 PACKAGED ROOFTOP UNIT

1.1 OCCUPANCY CONTROL

2.0 VAV AIR HANDLING UNIT WITH DB ECONOMIZER AND RETURN FAN

2.1 OCCUPANCY CONTROL WITH MORNING WARM-UP OR COOL DOWN

2.2 ENERGY SAVING TEMPERATURE RESET

2.3 STATIC PRESSURE CONTROL

2.4 ECONOMIZER CONTROL

2.5 AIR COOLED CHILLER CONTROL

1.0 PACKAGED ROOFTOP UNIT

1.1 OCCUPANCY CONTROL

When the DDC controller receives an occupied run command based on an occupancy schedule the morning warm-up or cool-down cycle is activated. The unit supply fan is energized. Outside air dampers remain closed and return air dampers are at the maximum position. During morning cool -down, when the zone temperature is above the occupied setpoint, the cooling system will be energized and all compressors will run until the zone temperature reaches the occupied cooling setpoint. (During morning warm-up, the electric heating coil will run its full capacity until the zones reach the occupied heating setpoint.) At that time, outside air dampers will open to the minimum outsider position and return air and relief dampers will modulate to the normal operating position and the rooftop unit will cool (or heat) to meet the user-adjustable occupied setpoint in response to a signal from the zone temperature sensor. When the DDC controller receives an unoccupied command, the DDC controller will de-energize the supply fan and the cooling system (or 2 stage Electric heating coil during heating mode) and the outside air damper will close and the return air and relief dampers will return to their normal position. If occupants are working outside normal scheduled times, they will be able to push a button on the thermostat which will change the mode of the unit from unoccupied to occupied for a preset period of time after which the unit will return to its unoccupied mode. When the rooftop unit is in the unoccupied mode and the zone temperature increases above the unoccupied cooling setpoint, (or falls below the unoccupied cooling setpoint) the unit will return to occupied mode and will run until the unoccupied setpoint is met. At which time the rooftop will return to the unoccupied mode.

2.0 VAV AIR HANDLING UNIT WITH DB ECONOMIZER AND

RETURN FAN

2.1 OCCUPANCY CONTROL WITH MORNING WARM-UP OR COOL DOWN

When the DDC controller receives an occupied run command based on an occupancy schedule the morning warm-up or cool-down cycle is activated. The unit supply fan is energized and a variable frequency drive on the supply fan and return fan ramp up to their maximum position and all VAV boxes are set to their maximum open position. Outside air dampers remain closed and return air dampers are at the maximum position (the warm-up or cool-down periods are preset to run for 10 minutes but can be readjusted by the users if necessary. The DDC controller will stop the cycle early if all zones have met their occupied setpoints). During morning cool -down, when the zone temperature is above the occupied setpoint, the chilled water control valve will be set to the maximum open position until all zone temperatures reach the occupied cooling setpoint. The hot water control valve remains completely closed during morning cool down mode. (During morning warm-up, and zone temperatures are below occupied setpoint, the hot water control valve will be set fully open position and will remain open until all zones reach the occupied heating setpoint or an adjustable 10 minute period has elapsed. (All other heating by the system except during the morning warm-up described here, will be done by the reheat coils in the VAV boxes. The chilled water control valve will remain fully closed during the morning warm-up heating mode. When the preset minimum in minute period elapses or when all zones are at occupied setpoint, (heating or cooling) The supply fan and return fan will ramp down to their minimum position or until the static pressure meets the static pressure setpoint. The return fan is set at a user adjustable 10% airflow below the supply fan airflow to maintain positive building pressurization. This differential is verified based on signals from the air monitor stations for supply fan and return fan Outside air dampers will open to the minimum outside air position based on a signal from the air monitoring station in the outside air intake and return air dampers open to the corresponding position as will the relief dampers. The DDC controller will modulate the chilled water valve to maintain a constant supply temperature with a starting value at 55°F (user adjustable) and a variable air volume box in each zone will modulate airflow as required to meet zone setpoint based on a temperature sensor located in the zone. If any zone reaches minimum airflow setpoint and the space temperature continues to fall, the DDC control system will modulate a hot water reheat valve located in the VAV box from closed to open position until space temperature is satisfied. As the variable speed drives modulate the fans, the minimum outside air entering will change with the supply air volume. The DDC controller will modulate the outside air dampers, return air dampers and relief dampers as required to meet the minimum outside air requirements at all times.

2.2 ENERGY SAVING TEMPERATURE RESET

In order to minimize the reheat required, the DDC controller will reset the supply air temperature from its 55°F initial setpoint to a user adjustable value of 63°F. When the air handling unit is in occupied mode the setpoint for the supply air temperature will be incremented up 1°F every 5 min. At the end of the first 5 min. if all zones served by VAV boxes are satisfied, the supply air temperature setpoints will be incremented up another 1°F and this will continue until any zone is above its cooling setpoint or a reaches the maximum setpoint of 63°F. Any time the supply air temperature is reset above its minimum, and any zone served by a VAV box is unable to maintain the zone setpoint, the DDC controller will increment the supply air temperature down until all zone temperatures can be met.

2.3 STATIC PRESSURE CONTROL

As each zone is being controlled by individual VAV boxes, the variable speed drive on the supply fan will modulate the fan speed as required to maintain the static pressure setpoint in the duct. The return fan variable speed drive will modulate the return fan speed to maintain a preset, adjustable differential between the supply and return fan for building pressurization. Supply and return air flows are verified by air monitor stations.

2.4 ECONOMIZER CONTROL

Economizer mode will allow outside air to be used to minimize cooling energy when it is at a lower dry bulb temperature than the return air temperature. (This can be operated on enthalpy difference also) When the air handling unit is in cooling mode and the outside air temperature is 60°F or below and above 40°F, the DDC controller will activate economizer mode. The DDC controller will close the chilled water control valve and modulate the outside air damper open until the supply air temperature meets the supply air setpoint. As the outside air damper is modulated open the return air damper will be modulate towards its minimum position and the relief dampers modulate to their maximum open position. If the outside air damper is completely open and the supply air temperature is still above its setpoint, the controller will begin opening the chilled water valve until the setpoint is met. If the supply air temperature falls below the setpoint the first action will be to reduce the chilled water valve position until it is fully closed and then the outside air damper will begin modulating closed until the setpoint is met. When outside air temperature reaches the user adjustable minimum setpoint for economizer operation, set initially at 40°F, the economizer mode is deactivated and normal control of the unit returns.

When the DDC controller receives an unoccupied command, the DDC controller will de-energize the supply fan and return fan and will close the chilled water valve (cooling mode) or hot water valve (heating mode) The outside air damper will close and the return air and relief dampers will return to their normal positions. If occupants are working outside normal scheduled times, they will be able to push a button on the zone temperature sensor which will change the mode of the unit from unoccupied to occupied for a preset period of time after which the unit will return to its unoccupied mode. During the current schedule for the air handling unit is changed to occupied mode during unscheduled times, the morning cool down or warm-up will not be activated. When the air handling unit is in the unoccupied mode and the zone temperature increases above the unoccupied cooling setpoint, (or falls below the unoccupied cooling setpoint) the unit will return to occupied mode and will run until the unoccupied setpoint is met. At which time the VAV air handling unit will return to the unoccupied mode.

Anytime this supply or return fans are commanded to be on or off but the fan status is not verified based on input from a current switch for each fan, an alarm will be sent by e-mail or text to the system operator designated to receive alarms.

2.5 AIR COOLED CHILLER CONTROL

When outside air temperature is above a user adjustable 55°F the air cooled chiller will be enabled. On a call for cooling from any equipment served by chilled water from this chiller, the DDC controller will start the lead pump. If the status of the lead pump of is commanded to run but this is not verified by a current switch on the pump, an alarm will be sent to the system operator and the standby pump will be started. The chiller will verify flow through its integral flow switch and when the flow is verified the chiller will and will be controlled by manufacturers’ internal controls. The chilled water setpoint will be set to 45°F but can be reset through the EMCS by the system operator. If the supply water temperature does not meet the setpoint for chilled water, an alarm will be sent to the system operator to notify him that the chiller has not started or is not running properly. (This system is a constant flow system with three- way control valves on all chilled water devices. Larger systems can be converted to variable speed pumping based on differential pressure in chilled water system.) When outside air temperature falls below 55°F the chilled water system including pumps will be de-energized and will be unavailable until the temperature climbs to or greater.