Xylem MM 221G Models 157S RBP MD Low Water Cut-Offs/Pump Controllers - Manual (Page 4)

K
4
STEP 3 - Electrical Wiring
a. Using a flathead screwdriver, remove the
junction box cover (K) by unscrewing the four
(4) cover screws.
• To prevent electrical shock, turn off the electrical power before making electrical connections.
• This low water cut-off must be installed in series with all other limit and operating controls installed on the
boiler. After installation, check for proper operation of all of the limit and operating controls, before leaving
the site.
• Modification of the switch assembly before or after installation could cause damage to the boiler and/or
boiler system.
• Boiler manufacturer schematics should always be followed. In the event that the boiler manufacturer’s
schematic does not exist, or is not available from the boiler manufacturer, refer to the schematics provided
in this document.
Failure to follow this warning could cause electrical shock, an explosion and/or a fire, which could result in
property damage, personal injury or death.
! WARNING
Switch Operation - Float Control
Switch Operation - Probe Control
Boiler feed pump off,
burner on, alarm off.
Boiler feed pump on,
burner on, alarm off.
Boiler feed pump on,
burner off, alarm on.
1 2 4 5 6 1 2 4 5 6 1 2 4 5 6
Water “ON” High Probe
1 8
7
6
2
L2
L1
3
4 5
COMMON
HIGH
PROBE
LOW
PROBE
GND
N.C. CONT.
N.O. CONT.
Water “OFF” Low Probe
1 8
7
6
2
L2
L1
3
4 5
COMMON
HIGH
PROBE
LOW
PROBE
GND
N.C. CONT.
N.O. CONT.