Xylem MM 712C Series 51/51 S/53 Replacement Float and Large Bellows Assembly - Manual (Page 2)

STEP 1 - Preparation
STEP 2 - Installation for Models 51, 51S, and 53
a. Clean gasket surfaces on head casting (B) and die casting and valve assembly (H).
b. Put gasket (K) in the recess on the head casting (B). Place the other gasket (L) over the bellow cup (J).
c. Install the bellow cup (J) into the head casting (B). Make sure the tab on the bellows cup fits into the
notch on the head casting.
d. Carefully slip die casting-and-valve assembly (H) over switch cam and attach it to head casting (B),
using the four (4) screws (G).
e. Screw float (E) into float arm (F) of bellow cup (J). Make sure float is screwed on all the way.
f. Install head casting (B) onto float chamber using new gasket (N) and six (6) bolts (A). Tighten in a
star pattern to 35 - 40 ft./lbs. (35-40 N•m).
g. Reinstall the piping and the No. 2 switch (P) if necessary.
a. If necessary, remove the four (4) screws that hold the No. 2 (P) switch and remove switch.
b. Remove piping from the valve assembly (H) only.
c. Remove the six (6) bolts (A) that hold the head onto the float chamber and remove the head flange (B).
d. Remove cotter pin (C) and pin (D) from the float arm and valve linkage.
e. Units manufactured before May 99 (99E) and starting February 05 (05B)
Use a wrench on both float and float arm to unscrew float (E) from float arm (F).
Units manufactured after May 99 (99E) through January 05 (05A)
Unscrew locking nut (M) and unscrew float (E) from float arm (F).
f. Remove four (4) screws or hex screws (G). Carefully slide die casting and valve assembly (H) over
switch cam and set aside. Remove bellows cup (J) from head casting (B).
2
Release pressure to 0 psi (0 bar) and let boiler cool to 80˚F (27˚C). Drain water level down below the float chamber.
Turn off all electrical power to the boiler.
Failure to follow this warning could cause property damage, personal injury or death.
! WARNING
Determine which series water feeder/low water cut-off you have from
figures 1 through 4 on page 3.
• Units manufactured before May 99 (99E) and starting February 05 (05B) use figure 1 or
NOTE: Units manufactured prior to May 99 (99 E) and those manufactured starting February 05 (05B)
have a simular design but use a different thread size. They are not interchangeable.
• Units manufactured after May 99 (99E) through January 05 (05A) use figure 2 or 4
NOTE: New replacement bellows cup (J) will require one time float (E) replacement. See figure 1 or 3.
Although similar, the floats and bellows assemblies from before May 1999 do not fit new assemblies.