Dettson AMP1-IE2 Guide D'installation Et Manuel Du Propriétaire page 42

5) SEALED COMBUSTION SYSTEM
(SCS) OPERATION
5.1) General:
Note: Refer to electric wiring diagram (figures # 6.7
and # 6.8) and parts list page # 31.
Normal operation
When thermostat calls for heat after a 3 seconds
period, the contact closed on T-T of primary control
terminal of the burner.
power to the burner motor and igniter. Then, After
valve-on delay period of 15 seconds, apply power to
the solenoid valve.
When the burner blower starts, a pressure is created
in the combustion chamber and a vacuum is created
in the burner casing. These pressures act on pressure
switches by opening the normally closed contact of
PS-1 pressure switch (open at 0.15'' W.C.).
important to know that the two pressures act in the
same way on the diaphragm pressure switch. In less
then four (4) seconds, the total pressure (see
article 5.2) should stabilize between 0.20'' and
0.70'' W.C. . The PS-2 normally opens contact close
at a pressure of 0.8'' W.C. and more. Therefore, the
PS-1 and PS-2 contacts are open in normal operation
of the heating unit.
Abnormal operation (during the prepurge period)
Sealed combustion system (SCS) incorporates a
safety shutdown system that will shut the burner off in
the eventuality of a blocked intake or blocked vent
outlet. After a call for heat, during the pre purge
period, if one of the pipe is blocked:
1. One of PS-1 and PS-2 contact closes (abnormal
total pressure).
2. The TDR-1 contact closes (after 4 seconds) and
the electric power is applied on the C coil of SPDT
relay.
3. The normally closed contact of SPDT relay opens,
burner motor and ignition system shut down
immediately.
4. The L-1 light stays on for the rest of pre purge
period plus the lockout timing of 15 seconds or 30
seconds depends on lockout timing (maximum
time is 41 seconds approximately)
5. The control enters in lockout state (see 5.3
article).
Primary control will apply
It is
Note: L-1 light ON during a certain time is an
indication of a problem with the SCS pressures or
the pressure switches.
Abnormal operation (flame shut down)
Sealed combustion system (SCS) incorporates a
safety shutdown system that will shut the burner off in
the eventuality of a totally or partially blocked intake,
totally or partially blocked vent outlet or an extremely
high wind. When flame is present, If the pressure is
out of the limits:
1. The pressure switches react and one of PS-1 and
PS-2 contact closes (abnormal total pressure).
2. The TDR-1 contact closes (after 4 seconds) and
the electric power is applied on the C coil of SPDT
relay.
3. The normally closed contact of SPDT relay opens,
burner motor, ignition system and valve shut down
immediately.
4. The L-1 light stays OFF in this case.
5. The control enters in Recycle mode (see 5.3
article).
6. When the control enters Trial and there is still a
problem, the system react according to ''Abnormal
operation (during the pre purge period)''.
5.2) Overfire pressure and burner casing
vacuum verification:
Verify that the pressure switches are in working order
by measuring the total pressure (addition of overfire
pressure and vacuum in the burner casing). Overfire
pressure reading are taken by removing the plug on
the observation door and the vacuum by removing the
plug on the top of burner casing. Use a differential
pressure gage 0 – 1.0 W.C. (see figure # 4). If the
burner enters in Lockout state, put a jumper
between # # 2 and # # 3 connection on the terminal
strip of the burner to temporary by-pass the safety
shut down system.
CAUTION
Remove the jumper after the verification
The total pressure must not be more then 0.8 W.C. If
it is the case, the pressure and vacuum can be
verified separately to identify the problem:
11