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8-13GFK-0787B Chapter 8 Installation Information
commanded state. If it does not, the point is pulsed Off again for about 7.5mS. A
maximum of two pulses of approximately 5mS and 7.5mS duration can occur. The 7.5mS
pulse occurs only if the volts feedback for the first pulse is incorrect.
Each output device’s characteristics should be checked against the list above to verify
that it can be autotested and/or used in the 4-block output group. Often, in cases where
a desired output device does not by itself meet a requirement, external components can
be added to change its characteristics and allow it to operate in a 4-block output group
and be autotested. Or, a diagnostic feature (such as autotest, No Load, or Overload) can
be disabled to allow it to operate in a 4-block output group. The following are two
examples.
GE Catalog Number CR120BDXXX48 Series A 600–Volt Industrial Relay
XXX represents a 3-digit number identifying the type and number of contacts.
This relay has a NEMA A600 rating: Maximum AC Voltage = 600
Maximum continuous current: = 10A
The 24 VDC coil typically draws 117 milliamps at 24 VDC when the relay is picked up.
This meets the GMR requirement of a minimum of 100 milliamps to be able to use the
No Load diagnostic without using additional external components to increase the load.
However, the 24 VDC coil is a dual winding type which draws a higher current during
the first part of the armature stroke. Its inrush current is approximately 9.8 Amps at
24 VDC, which causes an Overload diagnostic (overload=more than 2.8 Amps) to be
generated by the Genius output circuits. To overcome the high inrush current, the
Overload diagnostic must be set to NO for those outputs that would be wired to this
type or relay. This relay, with no external components, does not exhibit any chatter
during the output autotesting, although a flyback diode is still recommended to reduce
noise on the 24VDC power lines.
GE Catalog Number CR7RBXXEL Spectra 700 IEC Control Relay
XX represents a 2-digit number identifying the type and number of contacts.
This relay has a NEMA A600 rating: Maximum AC Voltage = 600
Maximum continuous current: = 10 A
The 24 VDC coil typically draws 230 milliamps at 24 VDC when the relay is picked up.
This also meets the GMR requirement of a minimum of 100 milliamps to be able to use
the No Load diagnostic without using additional external components to increase the
load. The inrush current for this relay is low enough that the Overload can be left
enabled. However, this relay, with no external components, does exhibit very minor
chatter during the output autotesting, although its contacts do not begin to open. A
flyback diode wired across the coil eliminates all the chatter and is also recommended to
reduce noise on the 24VDC power lines.