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SAFETY FOR LIFE

S260-75-1

Timer Settings

IMPORTANT: Put control in manual mode prior to changing timer setting. There is no fault current protection when in manual mode. Failure to comply can cause unintended operation.

The two digital timers are identical. One timer controls the time required to transfer from the preferred source to the alternate source, the other timer controls the time to transfer from the alternate source to the preferred source.

OUT Indicator

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

OUT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Display

 

 

 

 

39

49

5

 

 

 

 

 

3.45

 

 

 

 

 

Digital Time

 

 

 

 

 

 

 

 

 

 

 

 

Thumb-Wheel

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Time Setting

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

9 9 9

 

 

Decimal Point

 

 

 

 

 

 

 

 

 

 

S

 

 

Indicator

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Time Range

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Selector

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 15.

Digital Timer and Time Ranges.

The two digital timers feature the following informational indicators and adjustment controls:

Digital Time Display

LED displays the time count. The timer counts up until it reaches the time delay setting of the thumbwheel switch.

Time Range Selector

The time range selector switch can be set to six different positions with a flat screwdriver. Each position indicates a time range. See chart below. The time range selector is preset to the time range of 0.1 to 99.9 seconds.

 

9.99

99.9

999

99.9

999

99.9

 

Indication

S

S

S

M

M

H

 

 

 

 

 

 

 

 

 

Time

0.01

0.1

1

0.1

1

0.1

 

to

to

to

to

to

to

 

Range

 

9.99

99.9

999

99.9

999

99.9

 

 

 

 

sec

sec

sec

min

min

hours

 

 

 

 

 

 

 

 

 

Thumbwheel Time Setting

IMPORTANT: Thumb-wheel time setting must be securely turned. Incomplete setting may cause timer malfunction and control misoperation.

Set the desired time delay setting by rotating the thumb- wheel switch. For example, if the thumbwheel time setting is 345 the timer will time out in 34.5 seconds based off the time range selector setting of 0.1 to 99.9 seconds.

Note: The thumb-wheel time setting, which does not turn infinitely, should not be turned beyond the limit.

Out Indicator

The out indicator briefly lights to signal completion of a timing interval and confirm that the timer has operated.

Normal Operation

The control will react to ongoing line voltage conditions and operate automatically as programmed. If equipped with the fault block accessory, transfer to the alternate source may be prevented when loss of voltage is due to

aload-side fault. See Fault Block Operating Instructions section for procedure to restore service.

THEORY OF OPERATION —BASIC S CONTROL

Refer to Figures 16 and 17 for the following sections:

Voltage Sensing

The S control will transfer the load to an alternate source when one or more phases of the preferred source is lost, provided normal voltage is present on all three phases of the alternate source. To perform this function, the control requires three-phase, low-voltage (120 Vac) input from both the preferred and alternate sources of power. Input from Source I is connected to terminals A, B, C and G1 of TB2, and input from Source II is connected to terminals X, Y, Z and G2.

Each of the three input phase leads for both Source I and Source II is shunted to ground by a capacitor–varistor combination to provide surge protection to the control. On the preferred source side of the voltage sensing cir- cuitry, the input lines then pass through 10 Amp fuses to the voltage sensing relays: R2 (Phase A), R9 (Phase B) and R10 (Phase C). R9 and R10 are connected directly to the input while N.O. contacts of R9 and R10 are in series with the R2 coil. Thus, R2 can be energized only if all three incoming phase voltages are above a predetermined value (approximately 97 volts). A similar arrangement is used for the alternate source sensing relays. R6 can be energized only if R7 and R8 are energized. The transfer bus across the top of the schematic diagram), which provides the operating power for the control is normally energized from Phase Y. If R7 drops out, due to loss of Phase Y, R11 will be energized from Phase B (through N.C. contact of R7) to re-energize the transfer bus. The contacts of R7 and R11 are so connected that the transfer bus can never be simultaneously energized from both B and Y phases.

17