Time Mark 257 Data Sheet

MODEL 257

TIME MARK is a division of

3-Phase Monitor

⚫ Detects phase loss, low voltage, phase reversal

⚫ 50Hz, 60Hz and 400Hz models

⚫ Automatic or manual reset

⚫ Five year unconditional warranty

DESCRIPTION

The Model 257 continuously monitors 3­phase power lines for abnormal conditions.
When properly adjusted, the Model 257
monitor will detect phase loss on a loaded
motor even when regenerated voltage is
present.

This device consists of a solid-state voltage
and phase-angle sensing circuit, driving an
electromechanical relay. When correct
voltage and phase rotation are applied, the
internal relay will energize. A fault condition
will de-energize the relay. When the fault is
corrected, the monitor will automatically
reset (a manual reset version is also
available).

The Model 257 does not require a neutral
connection and can be used with Wye or
Delta systems. Voltage ranges are
sufficiently wide to allow for proper
adjustment to existing conditions. Both
“TRIP” and “NORM” condition indicators are
provided to aid in adjustment and system
trouble-shooting.

TYPICAL APPLICATION

SPECIFICATIONS

AUTO Reset
MANUAL Reset

Nominal AC
(phase to phase)

Case Color Gray Red Yellow Yellow Gray Red Yellow

Adjustment range 85-120VAC 160-240VAC 380-480VAC 300-400VAC 85-120VAC 160-240VAC 340-440VAC

Frequency 60Hz 60Hz 60Hz 50Hz 400Hz 400Hz 50Hz

Power
consumption

Transient
protection

Repeat accuracy ± 0.1% of set point (fixed conditions)

Response time 50ms drop out

Dead band Approximately 2%

Output contacts SPDT 10 amps at 240VAC resistive

Expected relay
life

Operating temp -20° to +131° F

Humidity
tolerance

Enclosure
material

Mounting 8-pin socket ( **sold separately)

Weight 5 ounces

Agency approvals UL Recognized* and CSA Certified

B257B

B257BM

120VAC 208/240VAC 480VAC 380VAC 120VAC 208/240VAC 415VAC

1.4W 2.4W 3.7W 3.0W 1.4W 2.4W 3.3W

Mechanical: 10 million operations
Electrical: 100,000 operations at rated load

*Conditions of acceptability: (1) the 380V and 480V versions must be used with a UL Recognized

600VAC socket. (2) For use in a Pollution Degree 2 environment (3) To be installed on the load side

257B

257BM

Shown with optional 8-pin socket

A257B

A257BM

of branch circuit protection rated 10A.

EX257B

EX257BM

2500VAC for 10ms

0 - 97% w/o condensation

ABS plastic cover

B257B-400

B257BM-400

** Order 8-pin socket number 51X120

257B-400

257BM-400

EX257B-415V

EX257BM-415V

DIMENSIONS

11440 East Pin e Str e et

Tul s a , O k laho m a 7 4 116

12/2018

© 2018 TIME MARK CORPORATION

MODEL 257

TIME MARK is a division of

3-Phase Monitor

READ ALL INSTRUCTIONS BEFORE INSTALLING, OPERATING OR SERVICING THIS DEVICE.

KEEP THIS DATA SHEET FOR FUTURE REFERENCE.

GENERAL SAFETY

POTENTIALLY HAZARDOUS VOLTAGES ARE PRESENT AT THE TERMINALS OF THE MODEL 257.

ALL ELECTRICAL POWER SHOULD BE REMOVED WHEN CONNECTING OR DISCONNECTING WIRING.

THIS DEVICE SHOULD BE INSTALLED AND SERVICED BY QUALIFIED PERSONNEL.

Installation Instructions

IN APPLICATIONS WHERE VOLTAGES IN EXCESS OF

WARNING

300VAC ARE TO BE MONITORED, BE CERTAIN TO USE
THE TIME MARK MODEL 51X120 8-PIN SOCKET, OR AN
EQUIVALENT UL APPROVED 600VAC RATED SOCKET.

INSTALLATION

Mount the 8-pin socket in a suitable enclosure. A NEMA-1
rated enclosure, designed for socket-mounted relays is
available from Time Mark Corporation.

Connect 3-phase power to terminals 3, 4, and 5 on the
socket. Phase rotation should be verified using a Time Mark
Model 108A or 108B Phase Sequence Detector.

Connect the load control wiring to the appropriate terminals
on the socket:

For motor control applications; use terminals 1 and 8.
For phase loss alarm applications; use terminals 1 and 2.

Insert the Model 257 into the socket and apply power. If the
contact does not transfer (green light ON), check that all
phases are present, and of the correct voltage. If power is
correct, rotate the level adjustment counter-clockwise.

If the contact still does not transfer, remove power and
reverse two of the three phase wires at the socket (phase
rotation is reversed). Re-apply power. The contact should
transfer to provide a signal path between pins 1 and 8.

NOTE: When installing the Model 257 monitor in areas of high
humidity or contamination, it is recommended that the base area
and all exposed metal parts of the socket be coated liberally with
a good quality silicone grease, such as Dow Corning DC-4 or DC­4X. Insert the unit into the socket and wipe off excess grease
around the base. This will prevent the entrance of moisture and
other contaminates into the base and socket areas.

ADJUSTMENT SETTINGS

The following procedure will allow the Model 257 to be
adjusted to achieve a trip point just below the nominal phase­to-phase voltage, where the unit is applied.

Rotate the adjustment control fully clockwise, or until the red
(TRIP) indicator illuminates.

Slowly rotate the adjustment control in a counter-clockwise
direction, just until the green (NORM) indicator illuminates.

At this point, the Model 257 is the most sensitive to irregular
power line conditions. If nuisance tripping occurs, turn the
control slightly farther counter-clockwise.

A more accurate setting will require the use of a 3-phase var­iac to lower the voltage to an exact measurable setting. Time
Mark also offers a factory set version of all models and voltage
ranges, for only a small additional charge.

TROUBLESHOOTING

Should the Model 257 Monitor fail to operate properly, check
that all three voltages are present, and are of the correct
voltage level and phase rotation (a Model 108A or 108B
Phase Sequence Detector should be used to verify phase
rotation). Check all fuses and verify that all wiring connections
are correct. If problems persist, contact your local Time Mark
Distributor, or the factory for assistance (Monday-Friday, 8
a.m. to 5 p.m. CST).

MANUAL RESET VERSIONS

IF YOU DO NOT WISH TO USE THE EXTERNAL RESET
SWITCH ON THE MANUAL RESET VERSION, YOU MUST
JUMPER PINS 6 AND 7. Refer to the Manual Reset 8-pin
diagram.

WARRANTY

This product is warranted to be free from defects in materials
and workmanship, and is covered by our exclusive 5-year
Unconditional Warranty. Should this device fail to operate
for any reason, we will repair it for five years from the date of
manufacture. For complete warranty details, see the Terms
and Conditions of Sales page in the front section of the Time
Mark catalog or contact Time Mark at 1-800-862-2875.

11440 East Pin e Str e et

Tul s a , O k laho m a 7 4 116

12/2018

© 2018 TIME MARK CORPORATION