Page 30 - Webster Service Manual

To meet the needs of today' s
fuel-efficient, downsized and
space efficient burners,
Webster's M34DM-3 incorpo-
rates improved access to both
the bleed valve and bypass
plug. Locating the bleed port plug assembly on the side
of the fuel unit provides the service technician with one
visible and accessible location to either bleed the fuel
unit or change the bypass plug without removing the burner.
In addition to improved access the M34DM-3 cleaner
blade has been thickened to provide a more robust
cleaning action. For maximum protection, an additional
line filter should be used in accordance with recom-
mended standard practice All of the BUNA-N elastomers
have been replaced with VITON to provide extended life
at critical locations within the fuel unit.
The M34DM-3 retains all the industry accepted, state-of-
the-art features of the M34DK-3 fuel unit. These include
faster fuel cut-off, improved priming on single pipe instal-
lations. This unit can easily replace your standard M34D
or A2VA residential pump.
The M34DM-3 is capable of maintaining a three gallon
per hour fire size at up to 150 PSI throughout its design
life. The M34DM-3 is factory preset to 100 PSI and is
adjustable to 150 PSI.
General Operation and Fuel Unit Oil Flow
The compact M34DM-3 Fuel Unit is engineered for ef fi-
cient pumping of Bio fuel. The cut-away view illustrates
the oil flow through an M34DM-3 operating in a one pipe
system, with a suction line and no return to the storage
A one pipe system is frequent ly used when the storage
tank is located above the fuel unit, or when automatic
venting is not necessary . Vacuum at the pump inlet
should not exceed 10” Hg. For this type of installation to
be reliable, the total system must be completely airtight.
During installation or servicing of the fuel unit, air may be
manually bled from the system through the side-located
bleed valve.
The M34DM-3 will provide up to 10” Hg of inlet vacuum.
The two pipe system (shown below), with both a suction
and return line is self-venting. This allows any air in the
system to escape and be returned to the storage tank
through the return line.
M34DM-3 Bio Pump