Product Data

L404A,B PRESSURETROL® CONTROLLERS
Location and Mounting
NOTE: For most accurate operation; add supplemental heat
to installations where the heat falls below -20°F
(-29°C). Never locate the controller where the
temperature falls below -35°F (-37°C), because
mercury in the switch freezes at this temperature.
When used with steam boilers, always mount the controller
above the water line in the boiler. A steam trap (siphon loop)
must always be connected between the controller and the
boiler (see Fig. 2) to prevent boiler scale and corrosive vapors
from attacking the diaphragm. The loop on the steam trap
must always be perpendicular to the face of the controller. If
the loop is parallel to the controller, expansion or contraction
of the loop tips the controller and causes inaccurate operation
of the switch.
The controller can be mounted:
a. alongside the pressure gauge,
b. in a fitting on the boiler provided by the
manufacturer,
c. at a remote location in case of excessive vibration,
d. in a special mounting on a low water cutoff.
4-1/2 TO 5-1/2
(
114.3 TO 139.7)
BOILER
14026
STEAM TRAP
(SIPHON LOOP)
TEE
PRESSURE
CONTROLLER
1
CORRECT
PRESSURE
GAUGE
2-1/4
(57.2)
DIA.
BOILER
INCORRECT
1
1/4 IN. BLACK IRON PIPE WITH 1/4 - 18 NPT EXTERNAL
TRHEADS ON BOTH ENDS. BEND THE STEAM TRAP
(SIPHON LOOP) TO LEVEL THE CONTROLLER.
M8934
A
Fig. 2. Right and wrong mounting of a steam trap (siphon
loop), with approximate dimensions in in. (mm).
Make all pipe connections in accordance with approved
standards. Use only a small amount of pipe compound to seal
the connection joints. Excess pipe compound can clog the
small hole in the fitting and prevent the controller from
operating properly.
To avoid leaks and damage to the case, use a parallel jaw
wrench on the controller hexagonal fitting. Do not tighten the
controller by hand by holding the case.
Leveling
A controller with a mercury switch must be accurately leveled
for proper operation. It is level when the leveling indicator (see
Fig. 7) hangs freely with its pointer directly over the index
mark inside the back of the case. Level the controller by
carefully bending the steam trap (siphon loop).
Mounting Alongside a Pressure Gauge
To mount the controller alongside a pressure gauge (Fig. 2),
remove the gauge. In its place, install a steam trap (siphon
loop) with a tee on top. Using elbows and pipe nipples, mount
the controller and pressure gauge on the ends of the tee.
Level the controller after installation.
Mounting on a Boiler
If it is not convenient to mount the controller alongside the
pressure gauge, install steam trap (siphon loop) in the fitting
provided by the boiler manufacturer. If there is no fitting,
mount the steam trap at a location recommended by the boiler
manufacturer. Screw the controller directly to the steam trap
and level the controller.
Mounting at a Remote Location
If there is excessive vibration at the boiler than can adversely
affect the operation of the controller, mount the controller at a
remote location. All piping from the boiler must be suitable and
solidly mounted. The piping must be properly pitched to drain
all condensation back to the boiler. A steam trap (siphon loop)
must be mounted between the remote piping and the
controller. Level the controller after installation.
Supervision of Atomizing Medium Pressure (Air or
Steam)—L404B
When air or steam is used as an atomizing medium in an oil
burner system, authorities having jurisdiction (approval bodies
and codes) often require a low limit to prevent opening the
main oil valve until sufficient atomizing pressure is present,
and to shut down the system when the atomizing pressure
falls too low.
The L404B is recommended for this application. It makes a
circuit when the pressure rises to the setpoint and breaks
when the pressure falls to the setpoint minus the differential
(Fig. 7).
Wiring
WARNING
Electrical Shock Hazard.
Can cause severe injury, death or equipment
damage.
Disconnect the power supply before beginning wiring
to prevent electrical shock or equipment damage.
5 95C-10187B–1