LOT 201.41 ESF Load Sequencer

Question 1

• LOT 201.41 ESF Load Sequencer*
• • *

What are the different modes of the ESF sequencers?

Answer 1

• *MODE I: SI Signal**
• ≥ 4 of 6 slave relays from ESF actuation cabinets giving SI signal*
• *MODE II: LOOP**
• UV on 4.16 kV bus [2/4]*
• *MODE III: SI AND LOOP**
• Conditions for MODE I and MODE II exist*

Question 2

• LOT 201.41 ESF Load Sequencer*
• • *

What is the MODE I sequence of starting loads?

Answer 2

• 6 Sec / 10 Sec:*
• *HHSI / LHSI**
• 15 Sec:*
• *Containment Spray** (1st Try)
• *RCFC (11/12)**
• 20 Sec / 25 Sec:*
• *CCW / ECW**
• 30 Sec:*
• *AFW**
• 35 Sec:*
• *CR / EAB HVAC (Emergency MODE)**
• *Essential Chilled Water Pump**
• *Standby Essential Chiller**
• 40 Sec:*
• *Containment Spray** (2nd Try / Locks in)
• 240 Sec:*
• *Running Essential Chiller(s)**
• 280 Sec:*
• *Sequence Complete**

Question 3

• LOT 201.41 ESF Load Sequencer*
• • *

If a MODE I sequence is in progress and a LOOP occurs, what will the ESF sequencer do?

Answer 3

Strips Bus and restarts in MODE III

Question 4

• LOT 201.41 ESF Load Sequencer*
• • *

Where are the ESF load sequencers physically located?

Answer 4

EAB 10’

Each sequencer has it’s own room

Question 5

• LOT 201.41 ESF Load Sequencer*
• • *

Plant Conditions:

• ESF DG in parallel with offsite
• SI occurs

What does the ESF DG load sequencer do?

Answer 5

Output bkr will open and then MODE I will occur

If output bkr does not trip within 1 sec, incoming breaker will trip, sequencer will strip bus w/ exception of LC breakers and MODE III sequence will run.

Question 6

• LOT 201.41 ESF Load Sequencer*
• • *

What does the sequencer reset button on CP003 do?

Answer 6

Resets MODE I, II, and III

• Initiating condition must of cleared
• Sequence Complete (280 sec)
• For SI, must reset SI 1^st (CP001)​

Reset button also on local panels

• Note:*
• Does not clear MODE I logic to MODE III. Must dispatch operator with key to reset locally (MODE I logic key switch).
• If not done, a LOOP will result in a MODE III.

Question 7

• LOT 201.41 ESF Load Sequencer*
• • *

What permissives must be met for the ESF DG output breaker to close during a MODE II or MODE III sequence?

Answer 7

95% of rated voltage and frequency achieved

6 sec TD from LOOP signal received

• *Breakers open for stripped loads**
• If breaker failed to open, the sequencer locks up*

Question 8

• LOT 201.41 ESF Load Sequencer*
• • *

What is the MODE II sequence of starting loads?

Answer 8

• 1 Sec:*
• *480 V Buses**
• 15 Sec:*
• *RCFC (11/12)**
• 20 Sec / 25 Sec:*
• *CCW / ECW**
• 30 Sec:*
• *AFW**
• 35 Sec:*
• *CR / EAB HVAC (Emergency MODE)**
• *Essential Chilled Water Pump**
• *Standby Essential Chiller**
• 240 Sec:*
• *Running Essential Chiller(s)**
• 280 Sec:*
• *Sequence Complete**

• Note:*
• Can manually initiate with unlabeled shielded red pushbutton on CP003.*

Question 9

• LOT 201.41 ESF Load Sequencer*
• • *

What is the purpose of the ESF load sequencers?

Answer 9

Prevent overloading ESF bus and associated Standby DG due to high motor starting currents

Question 10

• LOT 201.41 ESF Load Sequencer*
• • *

What is the MODE III sequence of starting loads?

Answer 10

• 1 Sec:*
• *480 V Buses**
• 6 Sec / 10 Sec:*
• *HHSI / LHSI**
• 15 Sec:*
• *Containment Spray** (1st Try)
• *RCFC (11/12)**
• 20 Sec / 25 Sec:*
• *CCW / ECW**
• 30 Sec:*
• *AFW**
• 35 Sec:*
• *CR / EAB HVAC (Emergency MODE)**
• *Essential Chilled Water Pump**
• *Standby Essential Chiller**
• 40 Sec:*
• *Containment Spray** (2nd Try / Locks in)
• 240 Sec:*
• *Running Essential Chiller(s)**
• 280 Sec:*
• *Sequence Complete**