Advertisement
LI
A POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
^ USE GREEN TERMINAL TO CONNECT CASE TO GROUND.
^ CONTACTS BREAK IN SEQUENCE ON TERMPERATURE RISE.
Ml 581
FIG. 7—RA817A WIRING DIAGRAM.
OPERATION
The schematic diagrams show all systems in the idle
condition:
•
Burner off, no call for heat.
•
Pyrostat contacts closed (RA116A).
•
"Cold"contactsclosed, "hot"contacts open (RA117A,
RA817A).
•
Safety switches closed.
•
All relays de-energized.
NORMAL OPERATING SEQUENCE
On a thermostat (or line voltage controller) call for heat,
the ignition, oil valve, and burner motor start. The safety
switch begins heating. Afterthe burner flame is established,
the stack temperature rises and expands the bimetal
detector element. The Pyrostat contacts open (RA116A) or
the "hot" contacts close and the "cold" contacts open
(RA117A, RA817A), de- energizing the safety switch heater.
The ignition circuit de-energizes (RA117A, RA817A only).
When the call for heat is satisfied, the system returns to
the idle condition.
IGNITION FAILURE
Iftheburnerflameis not established within approximately
75 seconds (nominal) of a thermostat (or line voltage
controller) call for heat, the Pyrostat contacts (RA116A) or
"cold" contacts (RA117A, RA817A) remain closed. During
that time, the safety switch is heated. If the burner flame is
not established after 75 seconds (nominal), the system
locks out and cannot be started again until the safety switch
is manually reset.
BURNER FLAME FAILURE DURING THE RUNNING
CYCLE
RA116A
The loss of burnerflame reduces the stacktemperature,
closes the Pyrostat contacts, and energizes the safety
switch. If the burner flame is not re-established within the
75 second (nominal) safety switch timing, the system locks
out and cannot be started again until the safety switch is
manually reset.
RA117A, RA817A
The loss of burnerflame reduces the stacktemperature,
opens the "hot" contacts, and shuts the system down by
de-energizing the 2K burner motor relay. After a one
minute (approximate) scavenging period, the "cold" con¬
tacts close and energize the safety switch heater. If the
thermostat (or line voltage controller) is still calling for heat,
the Protectorelay control makes one attempt to restart the
system. If the burner flame is not re-established in 75
seconds (nominal), the system locks out and cannot be
started again until the safety switch is manually reset.
POWER FAILURE DURING THE RUNNING CYCLE
A power failure shuts off the ignition and burner motor.
If the thermostat is still calling for heat when power is
restored, the stack temperature must cool and return the
system to the idle position. Once the system returns to the
idle condition, it begins the normal operating sequence.
7
68-0119
Advertisement
