Xylem MM 414B Series 150E and 157E Low Water Cut-Off/Pump Controllers For Steam Boilers and Other Level Control Applications - Manual (Page 15)

15
Valve #1
Valve #2
BLOW DOWN PROCEDURE:
When blowing down a control at pressure, the blow
down valves should be opened slowly. The piping needs
to be warmed up and stagant water in the drain piping
needs to be pushed out. Suddenly opening a blow down
valve causes steam to condensate, which creates water
hammer. Damage to components can occur when water
hammer occurs due to improper blow down piping.
For these reasons, McDonnell & Miller recommends a
dual valve blow-down system for each control.
Blow down the low water cut-off when the water level is
at its normal level (pump/valve off) and the burner is on.
• Open the upper “Positive Shut-off Ball Valve” (#1).
• Slowly open lower “Throttling Gate Valve” (#2).
• With both valves open, the water level will drop in
the sight glass.
• When the water falls below the level of the middle
probe, the pump or valve should turn ON.
• When the water falls below the level of the bottom
probe, the burner should turn OFF. NOTE: The
Red LED will turn ON to indicate low water condition.
• Slowly close the lower “Throttling Gate Valve” (#2).
• The water level should begin to rise and the burner
should turn ON (Red LED turns off) when the level
is at the middle probe. The pump or valve should
turn OFF when the water level rises above the top
probe postion.
NOTE: On manual reset models, the red reset button will
need to be pressed after the water level is restored to the
level of the middle probe before the burner will operate.
• Close the upper valve “Positive Shut-off Ball Valve” (#1).
• Observe that the water level returns to its normal level
before leaving the site.
To prevent serious personal injury from steam
pipe blow down, connect a drain pipe to the
control opening to avoid exposure to steam
discharge.
Failure to follow this caution could cause
personal injury.
! CAUTION
MAINTENANCE
SCHEDULE:
Blow down control as follows when boiler is in
operation.
• Daily if operating pressure is above 15 psi.
• Weekly if operating pressure is below 15 psi.
Disassemble and inspect annually.
• Inspect the float/probe chamber and equalizing
piping annually. Remove all sediment and
debris from chamber and/or equalizing piping.
• Inspect and clean probes. Use a non-abrasive
cloth to clean probes and water-side of
probe-mounting flange. Replace head mechanism
and probes if probes are worn, corroded or have
excessive coating of scale or rust that cannot be
easily cleaned off.
Replace head mechanism every 5 years.
More frequent replacement may be required when
severe conditions exist.
Replacement parts are available from your
local authorized McDonnell & Miller
Distributor. The use of parts or components other
than those manufactured by McDonnell & Miller
will void all warranties and may affect the units'
compliance with listings or regulating agencies.
WARNING
DO NOT REMOVE PROBES FROM FLANGE. Replace probe
flange assembly if probe Teflon
® insulation is broken, torn
or frayed.
NOTE
The probes may need to be inspected and cleaned more
frequently on systems where there is the potential of
coating build-up on the probes. This includes systems:
• With high raw water make-up
• With no condensate return
• With untreated boiler water
• Where significant changes have been made to the
boiler-water chemical treatment process
• With oil in the boiler water
NOTE
More frequent blow-down may be necessary due to
dirty boiler water and/or local codes.
NOTE
If this sequence of actions does not occur, as
described, immediately close all valves, turn off the
boiler and correct the problem. To correct the problem,
inspection/cleaning of all probes may be required.