Mounting on a Boiler
If it is not convenient to mount the controller alongside
the pressure gauge, install a 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 that 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 be-
tween 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 pres-
sure 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 set point, and
breaks when the pressure falls to the set point minus the
differential (Fig. 10).
1. Disconnect the power supply before beginning wiring
to prevent electrical shock or equipment damage.
2. Assume all wiring complies with applicable electrical
codes, ordinances, and regulations. Use NEC Class 1 (line
3. For normal installations, use moisture-resistant No. 14
wire suitable for at least 167!F (75!C) when you are using
the controller with a flame safeguard primary control, or at
least 194!F (90!C) when using it with a programming
4. For high temperature installations, use moisture-resis-
tant No. 14 wire, selected for a temperature rating above the
maximum operating temperature.
5. All models have a terminal block inside the cover (Fig.
3 and 4) and a 7/8 in. (22.2 mm) hole in one side for 1/2 in.
conduit, cable, or wires. Remove the front cover by loosen-
ing the screw at the bottom of the main scale.
6. Refer to Fig. 5 through 9 for typical hookups. Follow
the burner or boiler manufacturer's wiring diagram if pro-
7. Make sure the loads do not exceed the Switch Contact
Ratings in the Specifications section.
8. Replace the front cover when wiring is completed.
Fig. 3—L404 terminal blocks and internal
Fig. 4—L404 terminal block and internal
ON PRESSURE RISE TO SETPOINT.
SPDT SWITCH ACTION WITH JUMPER INSTALLED;
OTHERWISE, TWO ISOLATED SPST SWITCHES.
Fig. 5—L404 used as a limit or as an operating
PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION
HIGH LIMIT—L404A OR C BREAKS WHEN PRESSURE RISES
LOW LIMIT—L404B BREAKS WHEN PRESSURE FALLS TO SETPOINT
OPERATING CONTROLLER—L404A BREAKS WHEN PRESSURE RISES
TO SETPOINT, AND MAKES AGAIN WHEN PRESSURE FALLS TO
SETPOINT MINUS DIFFERENTIAL.
MAKES R-W ON