Flashcards in DG HVAC Deck (23):
List the Supply Fan Modes
2. AUTO 1
3. AUTO 2
Describe the "AUTO 1" mode of operation for Supply Fans.
Fan selected to AUTO 1 will start when any DG Cell reaches 85F. It will stop when all DG cells are less than 78F.
Describe the "AUTO 2" mode of operation for Supply Fans.
Fan selected to AUTO 2 will start when any DG cell reaches 90F. It will stop when all DG cells are less than 83F.
Power supplies to Supply Fans.
480 VAC MCC's DGA/B/C/D (via E5/6/7/8)
Describe the normal DG HVAC alignment for DG cells with no high temperature conditions.
One running building supply fan with two additional fans in standby alignment, running basement area exhaust fan, four tank vault ventilator fans running, and DG cell and emergency switchgear room exhaust fans aligned for automatic operation.
Describe the DG HVAC system response for rising DG cell temperature.
80F: Recirculation damper begins to close and exhaust damper begins to open (for that DG cell).
85F: Recirculation damper is fully closed and exhaust damper is fully open (for that DG cell).
85F in ANY DG Cell: Building supply fan in AUTO 1 auto starts. Five seconds later, the exhaust fans in ALL four DG cells automatically start.
90F in ANY DG Cell: Building supply fan in AUTO 2 auto starts.
DG HVAC system response for lowering DG cell temperature.
<83F in ALL DG Cells: Building supply fan in AUTO 2 stops.
<78F in ALL DG Cells: Building supply fan in AUTO 1 stops, the DG Cell exhaust fans stop, and cell recirculation/exhaust dampers reposition to normal standby lineup.
Describe the "AUTO" mode of operation for DG Cell Exhaust Fans.
Fan will automatically start, with a 5-second time delay, when ANY DG Cell temperature reaches 85F, and will automatically stop when ALL DG cell temperatures drop below 78F.
List the modes of operation for DG Cell Exhaust Fans.
List the modes of operation for Emergency Switchgear Exhaust Fans.
Describe the "ON" mode of operation for Emergency Switchgear Exhaust Fans.
Aligns the fan for automatic operation on switchgear room temperature; it does not directly energize the fan. The fan will automatically start at 82F in the respective switchgear room and will automatically stop at 75F decreasing.
Describe when to place the "ON" Supply Fan in "AUTO 1" and why it is done.
1. If ANY DG engine lube oil filter temperature is less than 130F, or
2. If any DG cell temperature is less than 65F.
This is done to prevent further cooldown of DLO and DG Cell, respectively.
Describe the operation of the 8 DG Cell Supply Dampers.
2 dampers per cell operated in pairs. Closing these dampers requires valving in pneumatics (nitrogen) in the mechanical equipment room (50' elevation). This action is required in the event of a fire in a DG Cell or 4160VAC Emergency Switchgear room.
Describe the operation of the 2 basement area supply dampers.
Pneumatically operated by instrument air, and operate in tandem with the basement area exhaust fan. A fan start actuates a solenoid that ports pneumatics to the supply dampers, and a fan stop secures power to the solenoid shutting the dampers.
What are the requirements for the basement area exhaust fan to run?
1. Fire detection must not detect any combustion products (smoke).
2. At least one building supply fan is running.
The basement area exhaust fan will stop if either of these conditions becomes unmet, and the supply dampers will shut in tandem.
Describe the operation of the volume control dampers and where there are located within the system.
8 volume control dampers are DG Cell Recirculation dampers (4) and Exhaust dampers (4). They are pneumatically operated by instrument air, and must be manually aligned to Exhaust for a fire by isolating pneumatics.
Describe the basic operation and/or actions required for a fire in a DG Cell or 4160VAC Emergency Switchgear rooms on 50' elevation.
1. Manually isolate instrument air to the affected cell exhaust and recirculation dampers, causing them to shift to an exhaust alignment.
2. Manually align nitrogen to the affected cell supply dampers to shut the dampers. This decreases airflow to allow spring operated fire dampers to actuate.
NOTE: DG Cell Exhaust Fans do not trip on fire detection, but the associated 4160VAC Emergency Switchgear room exhaust fan does.
Describe the automatic actions for a fire in a 480VAC or 4160VAC Switchgear room.
Exhaust fan for the associated room will trip.
Describe the automatic actions for a fire in the DG basement.
Building ventilation supply dampers (2) will automatically close (air removed from the actuators) and the exhaust fan will trip. The motor operated exhaust damper will automatically close when the exhaust fan trips.
State the Supply Fan requirement for EDG Operability.
If 2 or more Supply Fans are INOPERABLE, ALL EDG's are INOPERABLE.
State the Exhaust Fan requirements for EDG Operability.
1. If 2 or more Exhaust Fans are INOPERABLE, ALL EDG's are INOPERABLE.
2. If only 1 Exhaust Fan is INOPERABLE, the associated EDG is INOPERABLE.
State the limiting component for EDG OPERABILITY as a result of degraded ventilation.