HONEYWELL MODEL 700/800 SIGNAL PROCESSOR AND VIEWING HEAD
66-2069EP—04
4
installing any insulating material, for example a
rubber hose, in between the purge air line and the
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 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).
