Safety Function Of The 700; 700Ac Or 700Dc Signal Processor Proof Test Interval; The Flame Relay; Dependence Of The Pfd Avg On The Proof Test Interval For 700Ac - Honeywell 700 User Manual

HONEYWELL MODEL 700/800 SIGNAL PROCESSOR AND VIEWING HEAD

Safety Function of the 700

The safety function of the 700 signal processor consists of a
Flame Relay which comprises its safety function and behaves
as follows:
The Flame Relay (Normally Open)
• The Flame Relay will be energized when the signal
processor is powered and a flame on condition is detected.
• The Flame Relay will be de-energized when the signal
processor is powered, a flame of condition is detected, and
the FFRT (Flame Failure Response Time) has elapsed.
• The Flame Relay will be de-energized when the signal
processor is powered and detects a fault condition.
• The Flame Relay will be de-energized when power to the
signal processor is off.
As an added safety feature, the coil of the Flame Relay is
wired in series with a second pole of contacts on a Self Check
Relay. The Self Check Relay is designed to be closed during
normal operation of the signal processor and open during
detection of a fault or power down. It is physically impossible
for the Flame Relay to be closed if the Self Check Relay is
4.00E -04
3.50E
-04
3.00E
-04
2.50E
-04
2.00E -04
PFD
AVG
1.50E
-04
1.00E -04
5.00E
-05
0.00E
+00
0
Fig. 26. Dependence of the PFD
66-2069—01
700 AC PFD
1 2 3 4
AVG
open, unless the contacts of the Flame Relay are welded
closed or the contacts of the Self Check Relay are welded
closed. To reduce the chance of a false flame on condition, it
is recommended that the user wire the Flame and Self Check
Relays in series.
Also, as another added safety feature, neither relay can be
driven by a simple continuously high or continuously low
signal which could potentially be cuased by a fault. Each relay
must be driven by an alternating signal of the proper
frequency and duty cycle from the processor.
700AC or 700DC Signal Processor
Proof Test Interval
The Proof test must be conducted every 1 to 5 years. This
range is given to allow for the test to be performed during the
normally scheduled burner shutdown period. It is the
responsibility of the user to perform the proof test in the
specified time frame.
The following diagram presents the dependence of the
PFD on the proof test interval. The PFD
AVG
the proof test interval increases.
VS TIME
AVG
5 6 7
TIME (YEARS)
on the proof test interval for 700AC.
36
increases as
AVG
8 9 10
M35037