Honeywell 800 Series Manual page 4

HONEYWELL MODEL 700/800 SIGNAL PROCESSOR AND VIEWING HEAD
Signal Processor Power
Connections
The Model 700ACSP power and relay connections are
shown in Fig. 1. The AC power supply to the 700ACSP
Signal Processor passes through a 2A fuse and an inrush
current limiter.
The Model 700DCSP power and relay connections are
shown in Fig. 2. The maximum current requirement for
each 700DCSP is 250mA.
In the Model 700 signal processors the flame relay (RF
A/B ON, OFF, COM) has two sets of FORM C (SPDT)
contacts and the self-check relay (SC ON, OFF, COM) has
one set (Fig. 1 and Fig. 2). The self-check relay is
energized whenever the signal processor is powered and is
operating normally, whether the flame relay is energized
or not. Internally, the flame relay is wired in series with the
self-check relay (not shown), which prevents the flame
relay from energizing if the self-check relay is not
energized.
Unique fail-safe circuitry for the self-check and flame
relays ensure that in the event of any critical component
failure occurrence, system response will be to de-energize
66-2069EP—08
the self-check relay, which in turn de-energizes the flame
relay.
Some of the internal power wiring of the Model 700ACSP
and Model 700DCSP signal processors is shown in Fig. 1
and
Fig. 2. Rectifier diodes separate the battery backup input
from the main power bus until the battery voltage exceeds
the internal DC voltage plus a diode voltage drop.
Resettable fuses (shown as resistors with slashes) and
conventional fuses prevent internal failures from loading
the power sources.
With the Model 700DCSP, if a backup battery is to be used
with a main power supply, the two power sources would be
wired as shown in Fig. 2. If no backup battery is to be
installed, the main power supply can be connected at +26V
PWR and GND as shown in Fig. 2 or it can be connected to
the +24V BATT input and GND. It is preferable to use the
battery connections because it takes advantage of the
resettable fuse at the battery input; resettable fuses
recover automatically from a fault within a few seconds
after power is removed. At the +26V PWR input and its
associated GND, conventional1A fuses are used because
they are able to protect against 240VAC being applied by
accident (this could happen if a Model 700DCSP is
installed in a cabinet wired for a Model 700ACSP).
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