Essential Chilled Water (EC) Flashcards
What Auto starts the essential chillers?
SLAC-CC
SIAS
LOP
AFAS
CSAS
CREFAS
CRVIAS
What is the start sequence of the essential chillers?
How long after a start signal can the chiller be restarted?
T-0 – Chiller Circ pump starts immediately
T+23 seconds – Lube Oil pump starts
– Given 28 seconds to build up pressure and ensure bearings are lubricated
T+51 seconds – Chiller is started
20 minutes, unless an ESFAS signal is present. then it drops to 190 seconds (3 min 10 seconds)
What is the purpose of the variable inlet vanes in the essential chiller?
controls the rate at which liquid refrigerant flashes to vapor in the cooler
maintains chilled water outlet temperature at ~44*F
the essential chiller’s oil heater maintains oil temperature in the range of…?
130-150*F
What is the purpose of the Hot Gas Bypass in the essential chiller?
prevents surging during low load conditions
by opening a flowpath allowing hot compressor discharge to flow back to the cooler
this heats up and flashes some of the refrigerant, resulting in more flow from cooler to condenser
What is the purpose of the pump down unit in the essential chiller?
Transfers refrigerant to storage tanks when maintenance is required
What removes heat from the condenser section of the essential chiller?
EW (essential cooling water)
What is the purpose of the Refrigerant Head Pressure Control Valve (RHPCV)?
prevents stacking during low load conditions
by regulating EW flow through the condenser based on condenser pressure
What is the purpose of the flash economizer on the essential chiller?
intermediate pressure reservoir for liquid refrigerant before it is directed to the cooler
provides additional subcooling (improves efficiency)
What powers the EC circ pumps?
PHA/PHB
When will the EC circ pumps start?
whenever EC receives a start signal (auto or manual)
when the pump is started locally at the circ pump breaker
disconnect switch at the chiller (not normally used, inop’s chiller)
What is the purpose of the EC expansion tank?
What is the normal pressure of the tank?
monitoring for leakage
makeup
~28 psig N2
What signal would cause auto makeup to the EC expansion tank to automatically isolate?
Lo-Lo- level in the tank
How is EC flow throttled for most of the EC loads (automatically or manually)?
What is the one exception? How does this work?
manually throttled
Control Room essential
controlled by air temperature. cooling coils are normally bypassed when AHU isnt running
Where do the Control Room essential AHU EC valves get power from?
How do they fail?
PHA/PHB
as is
What EC system components have a SESS alarm?
Essential Chillers
EC Circ pumps
EC lube oil pumps
