5
A.
Intermittent Circulator Operation
1.
ROOM THERMOSTAT CLOSES
2. CIRCULATOR MOTOR ENERGIZED
a. As the thermostat closes its contacts, a low
voltage circuit (24V.) is completed to the bimetal
heater in the circulator relay (24A51). After
a time delay of 15 seconds, the main contacts
(120V.) of the circulator relay close to start the
circulator.
3. HEATING ELEMENT #1 ENERGIZED
a. Simultaneous with the completing of the circuit
for the circulator relay, two additional circuits
are completed.
b. The fi rst circuit is for the Heating Element
Relays which pull in immediately and the
second is for the bimetal heater in the #1 Heating
Element Sequencer (24A54).
c. These two circuits will be energized only if the
boiler is not “OFF” on limit.
d. After a time delay of 45 seconds (30 seconds
after the circulator has started) the main and
auxiliary contacts of the #1 Sequencer close;
the main contacts (240V.) energizing heating
element #1 and its pilot light (located at the
bottom of the side panel), the auxiliary contacts
(24V.) energizing the bimetal heater in the #2
Heating Element Sequencer.
4. HEATING ELEMENT #2 ENERGIZED
a. 45 seconds after bimetal heater in #2 Heating
Element Sequencer is energized, its main
contacts (240V.) and auxiliary contacts close;
the main contacts energizing heating element #2
and its pilot light (3
rd
lowest in the boiler), the
auxiliary contacts (24V.) energizing the bimetal
heater in the #3 Heating Element Sequencer.
5. HEATING ELEMENT #3 ENERGIZED
a. 45 seconds after bimetal heater in the #3 Heating
Element Sequencer is energized, its main
contacts and auxiliary contacts close; the main
contacts (240V.) energizing heating element #3
and its pilot light (2
nd
lowest in the boiler), the
auxiliary contacts (24V.) energizing the bimetal
heater in the #4 Heating Element Sequencer.
6. HEATING ELEMENT #4 ENERGIZED
a. 45 seconds after bimetal heater in #4 Heating
Element Sequencer is energized, its main
contacts and auxiliary contacts close, the main
contacts (240V.) energizing heating element #4
and its pilot light (highest in the boiler) – nothing
is connected to the auxiliary contacts.
SECTION II: OPERATING AND SERVICE INSTRUCTIONS
7. ROOM THERMOSTAT OPENS
8. HEATING ELEMENTS DE-ENERGIZED
When the thermostat is satisfi ed and opens its
contacts, the low voltage circuits to the Heating
Element Relay and the Heating Element Sequencers
are broken. The Heating Element Relays “drop-out”
immediately and totally de-energize the Heating
Elements and pilot lights. After a time delay of 45
seconds, the main contacts of all the Sequencers
“break” thus resetting the Heating Element Relays.
9. CIRCULATOR MOTOR DE-ENERGIZED
Simultaneous with the breaking of the low voltage
circuit to the Heating Element Sequencers is the
breaking of the low voltage circuit to the Circulator
Relay by the opening of the thermostat contact.
After a time delay of 90 seconds after all Heating
Elements are “off” the bimetal heater opens the
main contacts in the Circulator Relay thus stopping
the circulator. When the boiler is zoned with
circulator and switching relays as illustrated in
Figure 6 on Page 8 the circulator switch must be in
the “constant” position; therefore the circulator will
not have any delay when the thermostat(s) closes or
opens its contacts.
B.
Continuous Circulator Operation
If the Circulator Switch (located in the control portion
of the Boiler Jacket) is placed in the “CONT.” position,
the Circulator will run continuously and the Heating
Elements will sequence as in steps 3-6 and 8 above.
C.
Dual Limit Operation
The Dual Limit Control consists of two independently
adjustable temperature limits. The left hand adjustment
is for the safety limit and should be set initially for
220°F. The lower right hand adjustment is for the
operating limit and should be set for 210°F with a
differential setting (upper right hand adjustment) of 10º.
These adjustments may be varied to suit the individual
installation, with minimum of 10° difference between
the limit settings. If the setting of the operating Limit
or the safety limit is reached, the Heating Elements only
will be de-energized; the Circulator will continue to
run. If the Circulator Switch is in the “INT.” position,
the Circulator runs until the thermostat is satisfi ed and
the main contacts on the Circulator Relay open.
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