Honeywell L404T Manuel D’Utilisation

71-2429—2

4

Locate the L404F where the ambient temperature will not 

exceed 66°C (150°F). The L404F can be mounted near the 

pressure gauge, at a remote location, in a fitting provided by 

the boiler manufacturer, or in a special mounting on low water 

cutoffs. The L404F should always be mounted above the 

water line in steam boiler applications.

NOTE: For accurate operation, supplemental heat should be 

added to installations where temperatures fall below 

-29°C (-20°F).

A steam trap must be connected between the L404F and the 

boiler (see Fig. 2) to prevent boiler scale and corrosive vapors 

from attacking the elbows or diaphragm. 

To mount beside a pressure gauge, remove the gauge, and 

install in its place the steam trap with a tee on top. Mount the 

PressureTrol

®

 unit and pressure gauge on the side of the tee 

by means of nipples and elbows (see Fig. 2).

Excessive vibration at the boiler may affect the operation of 

the L404F. In these cases, the L404F should be remotely 

located, subject to the following:

1. All piping must be suitable and properly pitched to drain 

all condensation back to the boiler.

2. The remote mounting must be solid.

3. A steam trap must be used at one end of the piping.

If it is not convenient to mount the L404F adjacent to the 

pressure gauge, install a steam trap at the location 

recommended by the boiler manufacturer, then screw the 

device directly to the steam trap.

NOTE: For most accurate operation, supplemental heat 

should be added to installations where the 

temperature falls below -20°F (-29°C).These 

controllers can be mounted at any location in the oil 

supply line, depending on the application. Typical 

locations are shown in Fig. 3. The low oil pressure 

controller should be located upstream from the 

safety shutoff valve(s). In a downstream location, 

there would be zero pressure when the burner is not 

running and the safety shutoff valve(s) is (are) 

closed. This could prevent startup or require manual 

reset every time the burner is started. The high oil 

pressure controller should be located as near to the 

burner as possible.

Mount the oil pressure controller directly on the main pipe. 

Insert a tee in the pipe line, and connect a pipe nipple of 

appropriate size to the tee (see Fig. 4). Screw the hexagonal 

fitting (1/4-18 NPT internal thread) of the pressure controller to 

the pipe nipple. To avoid leaks and damage to the case, use a 

parallel jaw wrench on the hexagonal fitting close to the pipe 

nipple. Do not tighten the pressure controller by hand by 

holding the case. 

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 may clog the 

orifice in the pipe fitting and prevent the controller from 

operating properly.

4-1/2 TO 5-1/2

(114.3 TO 139.7)

BOILER

14026

STEAM TRAP

(SIPHON LOOP)

TEE

PRESSURE

GAUGE

PRESSURE

CONTROLLER

M8934B

1

1

1/4 IN. BLACK IRON PIPE WITH 1/4 - 18 NPT EXTERNAL 

THREADS ON BOTH ENDS AND 2-1/4 IN. DIAMETER LOOP. 

MAIN 

OIL

LINE

TO OIL

BURNER

ATOMIZER

ATOMIZING MEDIUM

(AIR OR STEAM)

MANUAL

SHUTOFF

VALVE

LOW OIL

PRESSURE

CONTROLLER

HIGH OIL

PRESSURE

CONTROLLER

RECIRCULATING 

VALVE AND SAFETY 

SHUTOFF VALVE

OIL 

PUMP WITH

PRESSURE RELIEF

LOW OIL

TEMPERATURE

STRAINER

MANUAL

SHUTOFF

VALVE

M17861