Xylem MM 221G Models 157S RBP MD Low Water Cut-Offs/Pump Controllers - Manual (Page 6)

Pump Control Only
1. Instal a starter or relay in pump control circuit,
as shown, to prevent damage to snap switch
and help insure proper switch/control operation.
Failure to do so may shorten the life of the
switch when actual amperage exceeds
switch rating.
2. Connect wires from holding coil of pump starter
or relay to terminals 1 and 2 as shown.
NOTE: To help insure most effective operation, bal-
ance boiler feed pump(s) to deliver required water
feeder rate to match boiler steaming requirements.
1 2 4 5 6
LOAD
LINE
6
WIRING DIAGRAMS
Low Water Cut-Off Only
1. Main Line Switch - For burner circuits within
the switch’s electrical rating.
1. Main Line Switch - For burner circuits within
the switch’s electrical rating.
2. Pilot Switch-To holding coil of a starter when the
burner circuit exceeds the switch’s electrical rating.
LINE LOAD
1 2 4 5 6
1 2 4 5 6
ALARM
NEUTRAL
HOT
ALARM
NEUTRAL
HOT
1 2 4 5 6
1 2 4 5 6
SEE PUMP
CONTROL
CIRCUIT
TO NEUTRAL
TO BURNER CONTROL CIRCUIT
HOT
ALARM
1 2 4 5 6
LOAD
LINE (3 PHASE) SEE PUMP
CONTROL
CIRCUIT
ALARM
1 2 4 5 6
LOAD
LINE
OR
OR
OR
Combination Pump Control, Low Water Cut-Off and Alarm
Alarm Circuit Only
1. Low Water Alarm 2. High Water Alarm
2. Pilot Switch - To holding coil of a starter when the
burner circuit exceeds the switch’s electrical rating.
1 8
7
6
2
L2
L1
N H
3
4 5
COMMON
Pump
AC SUPPLY
HIGH
PROBE
LOW
PROBE
GND
Securely tighten all electrical conductors
to terminals
N.C. CONT.
N.O. CONT.
CONTROL
HIGH
LEVEL
PROBE LOW
LEVEL
PROBE
ELECTRONIC PROBES: