18
TO
115V
SUPPLY
L1
N H
115V 60 CYCLE
SUPPLY
24 VOLT
THERMOSTAT
L2 T T
TO
24V
THERM
AQUASTAT
RELAY
A95602
Fig. 19 -- Wiring Connections to Aquastat Relay
Table 9 – Recommended Operating Control Settings
OPERATING CONTROL
CONTROL
SETTING
High Limit
Standing Radiators
180
°
F
Baseboard and
Convectors
200
°
F
Low Limit (When Used)
140
°
F
Differential (When Used)
10
°
F
1. Thermostat calls for heat completing circuit between
terminals T and T on L8124C aquastat controller
energizing the 1K relay coil.
2. With 1K relay coil energized, contacts 1K1 and 1K2 are
closed. Terminal B1 is energized providing power to
R4184 oil burner primary control. This in turn powers
ignition coil and burner motor.
3. With R4184 primary control energized, burner operation
starts and burner remains running as long as cad cell
senses flame. In the event of a flame failure or if flame is
not fully proven within 45 sec of initial start--up, the
R4184 primary control locks out and opens burner circuit.
This requires a manual start--up of burner.
4. As long as flame is proven through cad cell relay, burner
remains on until circuit is interrupted by boiler water
temperature reaching high limit setting (opening high limit
contacts BR), or thermostat is satisfied breaking T--T
circuit.
5. Circulator pump is powered through terminal C1 and runs
when boiler water temperature is above low limit setting.
6. If boiler water temperature reaches high limit setting, high
limit contacts BR open de--energizing terminal B1 and
shutting off burner. Circulator pump remains running as
long as thermostat calls for heat.
7. If boiler water temperature falls 10
_
below high limit
setting, contacts BR close energizing burner.
8. Thermostat is satisfied terminating call for heat. Relay coil
1K is de--energized opening 1K1 and 1K2 contacts. Both
burner and circulator pump cease operation.
NOTE
: The high limit setting must be set a minimum of 20
_
higher than low limit setting.
B.
Boiler Without Tankless Coil
AQUASTAT HIGH LIMIT CONTROLLER
The aquastat control’s high limit contacts open and turn off the
burner when the boiler water temperature reaches the control’s
high limit set point. The high limit contracts automatically reset
after the boiler water temperature drops past the set point by 10
_
F, which is a fixed differential. When the thermostat controls call
for domestic space heating, the sequence of operation for the
burner and circulator is as follows:
1. Thermostat calls for heat, completing the circuit between
terminals T and T on the aquastat controller, energizing
the 1K relay coil.
2. With the 1K relay coil energized, contacts 1K1 and 1K2
are closed. Terminals C1 and C2 are energized providing
power to the circulator. Terminal B1 is energized,
providing power to the oil burner primary control. This in
turn powers the ignition coil and burner motor.
3. With the primary control energized, the burner operation
starts and remains running as long as the cad cell senses
flame. In the event of flame failure or the flame is not fully
proven within the trial for ignition period, the primary
control will lockout and open the burner circuit. This will
require a manual startup of the burner.
4. As long as flame is proven through the cad cell relay, the
burner will remain on unit the circuit is interrupted by the
boiler water temperature reaching the aquastat’s high limit
setting (opening high limits contracts BR), or the
thermostat is satisfied breaking the T—T circuit.
5. If the boiler water temperature reaches the aquastat’s high
limit setting, the high limit contact BR is de--energized
turning the burner off. However, the circulator pump will
continue to run, as long as, the thermostat calls for heat.
6. After the high limit contact BR is de--energized, the boiler
water temperature must fall 10
_
F below the aquastat’s
high limit setting for the high limit contacts BR to close
and energize the burner.
7. When the thermostat is satisfied, the call for domestic
space heating is ended. Relay coil 1K is de--energized,
opening 1K1 and 1K2 contacts. Both the burner and
circulator pump operation stop.
BW
4
/BW
5