McDonnell & Miller MM 286 Series 1575 Low Water Cut-Off - Manual (Page 4)

4
When the water level in the boiler drops below the
middle probe, the circuit is broken which will
a c t i vate the pump relay, turning the pump on. W h e n
the water level rises above the shortest probe, the
circuit is made and the pump relay is deactiva t e d ,
t u rning the pump off. When the water level in the boiler drops below the
longest probe, the circuit is broken which will
d e a c t i vate the bu rner relay, turning the bu rner off.
When the water level is restored to the middle
p r o b e, the bu rner relay will be activated (bu rner on)
for auto reset controls only.
SWITCH SETTINGS:
Chamber
STEP 1 - Installation
TOOLS NEEDED:
One (1) pipe wrench, one (1) flathead screwdriver and/or 11/32" nut driver,
one (1) metal-cutting saw, one (1) 9/16" socket or wrench and pipe sealing compound.
If the control will be the primary low water fuel
cut-off, size the steam (top) and water (bottom)
equalizing pipe lengths to the chamber so that the
cut-off level mark is 1
1 /
2
" (38mm) below the
boiler’s normal water level, but not lower than
the lowest safe permissible water level, as
determined by the boiler manufacturer.
OR
If the control will be the secondary low water
fuel cut-off, s i ze the steam (top) and water (bottom)
equalizing pipe lengths to the chamber so that the
cut-off level mark is at or abov e the lowest safe
p e r m i s s i bl e water level, as determined by the
boiler manufacturer.
• Mount C o n t rol Box in a suitable location near
the boiler’s main electrical panel.
• Install electrical conduit between electrical
enclosure of the P robe Chamber and
C o n t rol Box .
• Pull four (4) wires through conduit.
Boiler sight glass must be visible from location of
Control Box and must be within 25 feet of Control
Box.
NOTE
R e fer to and fo l l ow local codes and standard s
when selecting conduit and electrical fittings.
Wires from Electrical Enclosure of the Pro b e
Chamber to Control Box must be in their own
c o n d u i t . If they are run in conduit with other wires,
there may be interference that can affect the
performance of the control.
NOTE
Wire must be 18 AWG stranded with glass braided
silicone jacket (UL 3071) suitable for high temper-
ature (200˚C) service.
NOTE
SPECIFICATIONS (cont.)