Xylem MM 226C User Manual

Series 69
Low Water Cut-Offs
For Steam Boilers

Applications:
For residential and commercial boilers of any
steaming capacity.

INSTRUCTION MANUAL

MM-226C

Series 69

WARNING

!

CAUTION

WARNING

• Before using this product read and understand instructions.

• Save these instructions for future reference.

• All work must be performed by qualified personnel trained in the proper application, instal­lation, and maintenance of plumbing, steam, and electrical equipment and/or systems in
accordance with all applicable codes and ordinances.

• To prevent serious burns, the boiler must be cooled to 80˚F (27˚C) and the pressure must be
0 psi (0 bar) before servicing.

• 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.

• We recommend that secondary (redundant) Low Water Cut-Off controls be installed on all
steam boilers with heat input greater than 400,000 BTU/hour or operating above 15 psi of
steam pressure. At least two controls should be connected in series with the burner
control circuit to provide safety redundancy protection should the boiler experience a
low-water condition. Moreover, at each annual outage, the low water cutoffs should be
dismantled, inspected, cleaned, and checked for proper calibration and performance.

• To prevent serious personal injury from steam blow down, connect a drain pipe to the control
opening to avoid exposure to steam discharge.

• To prevent a fire, do not use this low water cut-off to switch currents over 7.2A, 1/3 Hp at
120 VAC or 3.6A, 1/3 Hp at 240 VAC, unless a starter or relay is used in conjunction with it.

•

California Proposition 65 warning! This product contains chemicals known to the
state of California to cause cancer and birth defects or other reproductive harm.

•

Previous controls should never be installed on a new system. Always install new
controls on a new boiler or system.

Failure to follow this warning could cause property damage, personal inj ury or death.

CAUTION:



•

A more frequent replacement interval may be necessary based on the condition of
the unit at time of inspection. McDonnell Miller s warranty is one (1) year from date
of installation or two (2) years from the date of manufacture.

!

&

'

2

The 69 Series Built-in Low Water Cut-Off is furnished
with a threaded barrel casting which fits right into a
2 1/2" tapping provided by some boiler manufacturers
in the side of the boiler. Selection of the particular
model depends upon the insertion length into the
boiler (see chart). Order the built-in which provides
maximum insertion within the boiler.

0

2

0

4

1

0

3

0

0

2

0

4

1

0

3

0

0

2

0

4

1

0

3

0

SCHEMATIC OF TWIN SWITCH

INTERNAL OPERATION

NORMAL WATER LEVEL

FEEDER OR ALARM
OPERATING LEVEL

LOW WATER CUT-OFF
OPERATING LEVEL

NEUTRAL WIRE

NEUTRAL WIRE

HOT WIRE

HOT WIRE

TO BURNER

TO ALARM

SAFETY
SWITCH

0

2

0

4

1

0

3

0

USED AS MAIN LINE SWITCH

Diagram 1

Diagram 2

TO LINE

TO BURNER

STARTER

SAFETY
SWITCH

L1
L2
L3

0

2

0

4

1

0

3

0

USED AS PILOT SWITCH IN SERIES WITH
HOLDING COIL OF AUTOMATIC STARTER

NEUTRAL WIRE

TO

TWO WIRES OF 101A

OR TO ALARM CIRCUIT

HOT WIRE

TO BURNER

JUMPER

SAFETY
SWITCH

0

2

0

4

1

0

3

0

USED WITH MODEL 101 ELECTRIC

WATER VALVE OR IN ALARM CIRCUIT

Diagram 3 Diagram 4

IMPORTANT: Low water cut-off circuit of the 69 series must be electrically wired in series with all other boiler

limit operating controls.

Based on desired usage, connect wires from low water cut-off to appropriate control/alarm.

OPERATION

Maximum Steam Pressure: 20 psi (1.4 kg/cm2)

Electrical Ratings

Motor Switch Rating (Amperes)

Voltage Full Load Locked Rotor Pilot Duty

125 VA at

120 or 240 VAC

ABCDEF

Insertion

Model Length NPT

69 4

1

⁄8

(105)

169 3

1

⁄

8

(79)

269 2

1

⁄

4

(57) 1 (25) 4

1

⁄

8

(105)

1

⁄

8

(3) 2

1

⁄

2

9

1

⁄

2

(241)

369 1

3

⁄

4

(45)

469, 569 1

3

⁄

16

(30)

Dimensions, in. (mm)

NOTE: MV models are rated at 24 VA @ 24 VAC to 120 VAC

A

F

C

120 VAC

240 VAC

7.4 44.4

3.7

22.2

D

CUT-OFF

LEVEL

B

E

12

34

AA

OFF

ON

• Turn the boiler off.

• Drain the water in the boiler to a level which is below the
tapping on the boiler. Allow the boiler to cool to 80˚F (27˚C)
and allow the pressure to release to 0 psi (0 bar).

• Determine where to install the control. The low water cut-off
must be positioned at or above the boiler manufacturer’s
minimum safe water level.

• Separate the mounting barrel from the control slightly by
loosening the eight (8) slotted screws on the clamping ring.
This allows the barrel to be turned into the tapping in the
boiler without rotating the whole control. (The barrel may
also be completely removed to install easily).

• Apply a small amount of pipe dope or thread sealant to the
2 1/2 NPT and hand screw the barrel into the boiler without
rotating the rest of the control. Tighten the barrel securely
using a pipe wrench to about 150 ft-lbs. (200 N•m) torque.

• Rotate the control in the barrel to the finished position using
a level to set the two (2) conduit housing screws (AA) in a
horizontal position. Complete the installation by securing the
control onto the barrel by tightening the eight (8) clamping
ring screws to 5 ft-lbs (7 N•m) torque. "TOP" on the switch
terminal panel MUST be in the up position.

INSTALLATION –

TOOLS NEEDED:

One (1) flathead screwdriver, one (1) level indicator
and one (1) pipe wrench.

3

Installation of the Low Water Cut-Off

The center line on the casting of the Series 69 must be installed above the lowest permissible water level
determined by the boiler manufacturer.

Whether the gauge glass is mounted directly into the boiler or on an independent water column, the cut-off line on
the 69 control should be mounted 1/2” (15mm) above the lowest visible point of the gauge glass.

IMPORTANT: Follow the boiler manufacturer's
instructions along with all applicable codes and
ordinances for piping, blow down valve and water
gauge glass requirements.

NOTE: To connect wires to the terminals on
the water feeder, burner, or low water cut-off,
place the bare end of the wire under the termi­nal screw and tighten the screw with a flathead
screwdriver.

Cover

Using a flathead screwdriver, remove the one (1)
screw that secures the switch cover.

minimum safe

water level

Cut-off

level

Clamping ring

and 8 screws

AA