L8124A,B,C,E,G,L,M AQUASTAT® RELAYS
60-2061—10
10
Fig. 16. L8124E in a 24V, gas-fired forced hot water, tankless, zoned pump system.
OPERATION
High Limit Controller
The high limit opens and turns off the burner when the
water temperature reaches the set point. The high limit
automatically resets after the water temperature drops
past the set point and through the 10°F (6°C) differential.
Low Limit and Circulator Controllers
On a temperature rise, with the adjustable differential at the
minimum setting of 10°F (°C), the burner circuit (R-B) breaks
and the circulator circuit (R-W) makes at the control set point.
On a temperature drop of 10° F (6°C) below the set point, the
R-B circuit makes and the R-W circuit breaks. See Fig. 22.
At any differential setting greater than 10°F (6°C), the R-B
make temperature and R-W break temperature will remain the
same (control setting minus 10°F (6°C). The R-B break and
R-W make temperature will be the set point temperature plus
the difference between the differential setting and 10°F (6°C).
EXAMPLE:Set point of 140°F (60°C) differential set at 25°F
(14°C). On a temperature rise, R-B will break and R-W will
make at 155°F (68°C). On a temperature fall, R-B will make
and R-W will break at 130°F (54°C).
On the L8124M, the burner and circulator circuits are
controlled separately—the low limit controls the burner circuit
(R-B) as described above, while the low voltage thermostat
directly controls the circulator circuit (see Fig. 18).
SETTING AND CHECKOUT
WARNING
Fire or Explosion Hazard.
Can cause severe injury, death or property
damage.
Use product only in a system with a pressure relief
valve.
Setting
Follow the boiler manufacturer recommendation when making
the L8124 settings. The high limit setting must be at least 20°F
(11°C) higher than the low limit setting. Place the indicators
over the selected temperature marks. The low limit differential
is set by turning the differential adjustment knob to the desired
amount of differential.
Setting Stop
A setting stop (Honeywell part no. 126580, ordered
separately) may be installed on the adjusting knob to prevent
turning the knob beyond a predetermined point. Fig. 23 shows
it installed on the high limit switch knob to prevent setting
higher than 200°F (93°C).
IMPORTANT
The setting stop cannot be reset once it is in place. If
the stop must be removed, snip it off with cutters; do
not twist it off.
L1
(HOT)
L2
1
2
3
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
CONTROL CASE MUST BE CONNECTED TO EARTH GROUND. USE GROUNDING SCREW PROVIDED.
B1 IS 1/4 IN. TAB TERMINAL.
T
T
1
2
3
4
5
6
M1794A
TH
1
2
3
TR
LOW VOLTAGE
GAS VALVE
(eg, VR8300)
L8124E
AQUASTAT® RELAY
G
L2
L1
C1
C2
T
T
B2
B1
T87F
R845 RELAY
T
T
1
2
3
4
5
6
T87F
R845 RELAY
T
T
1
2
3
4
5
6
T87F
R845 RELAY
PUMP
PUMP
PUMP
