Xylem MM 226C User Manual

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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.

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.

SCHEMATIC OF TWIN SWITCH

INTERNAL OPERATION

NORMAL WATER LEVEL

FEEDER OR ALARM OPERATING LEVEL

LOW WATER CUT-OFF OPERATING LEVEL

NEUTRAL WIRE

HOT WIRE

TO BURNER

TO ALARM

SAFETY SWITCH

USED AS MAIN LINE SWITCH

Diagram 1

Diagram 2

TO LINE

TO BURNER

STARTER

SAFETY SWITCH

L1 L2 L3

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

NEUTRAL WIRE

TWO WIRES OF 101A

OR TO ALARM CIRCUIT

HOT WIRE

TO BURNER

JUMPER

SAFETY SWITCH

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

⁄8

(105)

169 3

⁄

(79)

269 2

⁄

(57) 1 (25) 4

⁄

(105)

⁄

(3) 2

⁄

(241)

369 1

⁄

(45)

469, 569 1

⁄

(30)

Dimensions, in. (mm)

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

120 VAC

240 VAC

7.4 44.4

3.7

22.2

CUT-OFF

LEVEL

OFF

• 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.

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

Wiring Instructions

• To prevent electrical shock, turn off the electrical power before making electrical connections.

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

TOP LEFT BOTTOM RIGHT

TOP12

Electrical connector is movable into any one of four positions illustrated, by simply removing two black headed screws and rotating housing.

NOTE: This control should be wired with materials suitable for use at 75˚C.

Switch Operation

The No. 11 switch can be identified by a black terminal panel. The switch contains two (2) single pole single throw switches to control the water feeder and the low water cut-off. The low water cut-off switch is between terminals marked “1” and “2”. A second switch is located between terminals marked “3” and “4”. This can be used to operate a low water alarm or a McDonnell & Miller electric water feeder.

Wiring Diagrams: Series 69 Low Water Cutoff with M&M Model 101-A Electronic Water Feeders

120V Burner and 120V Feeder

BURNER

120 VAC SUPPLY

101A

Using a wire nut, connect a wire from the neutral side of the power supply to one of the wires inside the feeder's junction box. (Does not make a difference which one). Connect a wire from the "hot" side of the power supply to terminal 2 of the Series 69 junction box. Connect the neutral side of the power supply to the burner. Connect the wire from the burner to terminal 1 of the low water cut-off. Connect a "jumper" from terminal 2 to terminal 3 of the low water cut-off. Connect a wire from terminal 4 of the low water cut-off to the remaining wire in the 101-A water feeder.

24V Burner and 24V Feeder

BURNER

101A-24

120 VAC SUPPLY

24V TRANSFORMER (101-24V-48)

12 34

24V

Connect the "hot" wire from the boiler transformer to terminal 2 of the low water cut-off. Connect the "hot" side of the water feeder transformer to terminal 3 of the low water cut-off. Connect the neutral side of the boiler transformer to the burner. Using a wire nut, connect the neutral side of the water feeder transformer to the water feeder. Connect the wire from the burner to terminal 1 of the low water cut-off. Connect a wire from terminal 4 of the low water cut-off to the remaining wire in the water feeder.

To prevent damage to the water feeder, a McDonnell & Miller transformer Model 101-24V-48 must be used.

IMPORTANT

BURNER

101A

120 VAC SUPPLY

24V

12 34

Wiring Alternatives - Controls of Different Voltages

For 120V Burner/24V Feeder setups For 24V Burner/120V Feeder setups

BURNER

101A-24

120 VAC SUPPLY

24V TRANSFORMER (101-24V-48)

TO AVOID DAMAGE TO 101A SOLENOID COIL, TRANSFORMER 101-24V-48 MUST BE USED.

12 34

Wire only terminals 1 and 2 into the millivolt circuit. Do not attach any other wiring to terminals 1 and 2.

Install wire (A) from water feeder to 120 volt Neutral wire. Install wire (B) from water feeder to terminal 4 of the low

water cut-off. Install wire (C) from terminal 3 of the low water cut-off to 120

volt Hot wire.

MILLIVOLT

BURNER CIRCUIT

101A

FEEDER

120 VAC SUPPLY

HOT

NEUTRAL

WIRE NUTS

Models 69-MV-P and 369-MV Millivolt Burner Circuit Controls with Water Feeder Millivolt Burner Control and Model 101-A 120V Water Feeder

24V TRANSFORMER

(101-24V-48)

101A-24

120 VAC

SUPPLY

WIRE NUTS

MILLIVOLT

BURNER CIRCUIT

Wire only terminals 1 and 2 into the millivolt circuit. Do not attach any other wiring to terminals 1 and 2.

Install wire (A) from 120 volt circuit Neutral wire to the transformer input Neutral terminal.

Install wire (B) from burner circuit Hot wire to the transformer input Hot terminal.

Install wire (C) from transformer output Neutral terminal to the water feeder.

Install wire (D) from the water feeder to terminal 4 on the low water cut-off.

Install wire (E) from terminal 3 on the low water cut-off to the transformer output Hot terminal.

Millivolt Burner Control and Model 101-A 24V Water Feeder

To prevent damage to the water feeder, a McDonnell & Miller transformer Model 101-24V-48 must be used.

IMPORTANT

To prevent damage to the water feeder, a McDonnell & Miller transformer Model 101-24V-48 must be used.

IMPORTANT

24V Burner/120V Feeder

120V Burner/120V Feeder

24V Burner/24V Feeder

Connect a wire from the "Hot" side of the power supply to the water feeder terminal 3, and low water cut-off terminal 2. Connect a wire from the neutral side of the power supply to the water feeder terminal 2, and to the neutral side of the burner.

Connect the wire from the burner to terminal 1 of the low water cut-off. Connect a jumper from terminal 2 to terminal 3 of the low water cut-off. Connect a wire from terminal 4 of the low water cut-off to terminal 1 of the water feeder.

120V Burner/24V Feeder

Switch Initial Initial Dwell/Feed

Position Dwell Feed Cycles

M&M 60 60 Repeats until LWCO

seconds seconds reactivates the

burner circuit

2 90 90 One

seconds seconds

3 100 100 One

seconds seconds

Wiring Diagrams (continued): Series 69 Low Water Cut-off with M&M Model WF-2-U Electronic Water Feeders

The Uni-Match®water feeders have a three-position

slide switch which initiates a dwell period specific to the position of the switch. If the system condensate raises the boiler water level above the cut-off level during the dwell period, no additional water will be added to the boiler. Once the dwell period has passed, the feeder will be activated and water will be added to the boiler. The feeder will be deactivated when the LWCO reactivates the burner circuit.

The position of the slide switch also sets the length of the dwell period, the length of time valve is open and the number of dwell/feed cycles. The control is set with the slide switch in position 3 and can be changed in the field after installation. The chart on the right indicates the cycles and length of dwell/feed cycles for each position.

WIRING ALTERNATIVES

WHEN USING MIXED VOLTAGES

M&M

BURNER

WF2-U-120 or WF2-U-24

12 3 4

W or

Supply Voltage SAME as Feeder

24V

TRANSFORMER

BURNER

12 3 4

WF2-U-120

BURNER

12 3 4

WF2-U-24V

120 VAC SUPPLY

120 VAC

SUPPLY

24V TRANSFORMER

TESTING

• Manually fill boiler until water level in the sight glass is above the control.

• Turn on the power to the boiler and water feeder. Activate the burner by raising the thermostat set point.

• Using the sight glass as a reference, slowly drain water from boiler by opening the blow down valve or the boiler drain until the low water cut-off activates the water feeder.

IMPORTANT: If the water feeder does not activate before the water level reaches the bottom of the sight glass, immediately close any open drain or blow down valve and check controls and piping for proper installation. Correct any problems.

• Continue to drain the boiler slowly. If the burner does not turn off before the water level reaches the bottom of the sight glass, immediately close any open drain or blow down valve. Check control for proper installation. Correct any problems.

• Once the burner turns off on low water, close all boiler drains or blow down valves.

• Using the sight glass as a reference, see that the water feeder activates and fills to approximately 1/2” to 1” (13 - 25mm) above the burner cut-off level of the low water cut-off.

IMPORTANT: If the water feeder does not turn off once the water level has surpassed the halfway point of the sight glass, immediately turn off the power to the boiler and water feeder and check control for proper installation. Correct any problems.

• Repeat test 2 or 3 times. Restore boiler and controls to normal settings.

INSTALLATION COMPLETE

LWCO

Level

Cover

Switch

Housing

Replace the cover on the switch housing and, using a flathead screwdriver, tighten the one (1) screw to approximately 2 ft•lb (2.6 N•m).

TROUBLESHOOTING

Problem:

1. Burner does not shut off on low water.

a. Cause: Float shield is loaded with mud or sedi-

ment. Shield may be out of position or damaged; bellows folds obstructed.

Test: With water level below the control check if

terminals 1 and 2 are open. If not, remove switch and manually test if terminals 1 and 2 can be opened.

Solution: Remove the control and clean. At this time,

check for a build-up of scale or sediment between corrugations of the bellows.

b. Cause: Contacts are fused together.

Test: Remove switch and operate manually to ver-

ify proper switch operation.

Solution: Replace switch. Check electrical load and

make sure it is within the ratings of the switch.

MAINTENANCE

SCHEDULE:

• Blow down weekly (at least once) when the

boiler is in operation.

• Disassemble and inspect annually. Replace

the low water cut-off if it is worn, corroded,

or if components no longer operate properly.

• Inspect the shield, float and bellows annually. Remove all sediment and debris.

• We recommend replacement when the switch no longer operates properly.

If you choose to replace the switch, order the McDonnell & Miller replacement switch and follow the Repair Procedure provided.

• Replace the low water cut-off every 10 years.

More frequent replacement may be required when severe conditions exist such as rapid switch cycling, surging water levels, and use of water treatment chemicals.

2. Electric water feeder does not shut off.

a. Cause: Float obstructed or damaged. Build-up of

scale or sediment between corrugations of the bellows. Shield may be out of position.

Test: With water level above the control, check if

terminals 3 and 4 are open. If not, remove switch and manually test to verify terminals 3 and 4 can be opened.

Solution: Check the clearance of the shield; replace

or clean the bellows.

b. Cause: Contacts are fused together.

Test: Remove switch and operate manually to

verify proper switch operation.

Solution: Replace switch. Check electrical load and

make sure it is within the ratings of the switch.

PROCEDURE:

CAUTION

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

Failure to follow this caution could cause personal

injury.

Test the low water cut-off when the water level is at its normal level and the burner is on. Slowly open the boiler drain valve and observe the water level fall in the gauge glass. Close the valve after verifying that the alarm/feeder contacts have closed and the burner shuts off. If this does not happen, immediately shut off the boiler and correct the problem.

Xylem Inc.

8200 N. Austin Avenue Morton Grove, Illinois 60053 Phone: (847) 966-3700 Fax: (847) 965-8379 www.xyleminc.com/brands/mcdonnellmiller

McDonnell & Miller is a trademark of Xylem Inc. or one of its subsidiaries.

Xylem MM 226C User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual