Xylem MM 273E User Manual

Model 750-HW-MT-120

5-1/2"

odel

-MT

Con

Uni

Probe Type High Water Manual Reset Control Unit

Applications: Conductance type control for steam boilers when a manual reset high water alarm or cut-off is required.

INSTRUCTION MANUAL

MM-273E

Model 750-HW-MT-120

Control Unit

WARNING

• Before using product, read and understand instructions.

N O I T

IN N R

• Save these instructions for future reference.

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

• 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.

• To prevent serious burns, allow the control and surrounding equipment to cool to 80˚F (27˚C) and allow pressure to release to 0 psi (0 bar) before servicing.

• To prevent an electrical fire or equipment damage, electrical wiring insulation must have a rating of 167˚F (75˚C) if the liquid's temperature exceeds 180˚F (82˚C).

• This control can be installed in series with all other limit and operating controls installed on the boiler. After installation, check for proper operation of all the limit and operating controls, before leaving the site.

• When using mixed voltages, do not jumper from terminal 1 to terminal 3.

• To prevent electrocution, when the electrical power is connected to the control, do not touch the terminals, or electrical wires.

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

•

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 fo

llow this warning could cause property damage, personal injury 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.

SPECIFICATIONS

The Model 750-HW-MT-120 control provides continuous protection against a high water condition in steam boilers. It can be used to interrupt the burner circuit to turn off the burner, interrupt the feedwater pump circuit to turn off the pump, or both. The control can also be used to provide an alarm (light, horn or both) when a high water condition occurs. The manual reset function will require that the unit be reset after water has dropped below the level of the probe.

Manual Reset

If a high water condition occurs (water is on the probe),

the Burner will turn Off. The Manual Reset button must

be pressed to make the control back to function after the

water level drops below the probe.

Control Unit Temperature Ratings:

Storage: -40˚F to 135˚F (-40˚C to 57˚C)

Ambient: 32˚F to 120˚F (0˚C to 49˚C)

On Manual Reset Units, if the control is in high water

condition (water reaches the probe) and there is an

interruption of electric power, the Burner will remain off

even if power is restored. The Reset button must be

depressed to make the control back to function after

the water level drops below the probe.

est

Green

Power On

High

Water

Model

Type

robe

5-1/2"

ontr

Reset Button

HW-M

Water

igh

l Unit

120

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Humidity: 85% (non-condensing) Electrical Enclosure Rating: NEMA 1 General Purpose

RS-1-BR1 Remote Sensor Maximum Steam Pressure: 250 psi (17.6 kg/cm2) Maximum Water Pressure: 250 psi (17.6 kg/cm

)

Maximum Water Temperature: 406˚F (208˚C) Electrical Enclosure Rating: NEMA 4X Watertight,

Corrosion Resistant

Connection Size: 1” NPT RS-1-LP

Maximum Steam Pressure: 15 psi (1.0 kg/cm2)

Maximum Water Pressure: 160 psi (11.2 kg/cm

)

Maximum Water Temperature: 250˚F (121˚C) Electrical Enclosure Rating: NEMA 1 General Purpose Connection Size: 3/4” NPT

Electrical Specifications

Motor Switch Rating (Amperes)

Model Voltage Full Load Locked Rotor Pilot Duty

120 VAC

120 VAC 7.2 43.2

240 VAC 3.6 21.6

125 VA at

120 or 240 VAC

50 or 60 Hz

Control Voltage: 120 VAC Hz: 50/60 Control Power Consumption: 3 VA (max.) Probe Sensitivity: 20,000 ohm

STEP 1 - Where to Install the Remote Sensors

Upright or Vertical

Position

Sideways or Horziontal

Position

Determine where to install the remote sensor (sold separately) based on the following requirements:

Option A a. The Remote Sensor can be installed directly in a 1"

or larger tapping in the top of the boiler.

b. The probe of the RS-1-BR-1 Remote Sensor will

need to be cut to appropriate length based upon the level where high water cutoff/alarm is desired.

c. The probe of the RS-1-LP Remote Sensor is

approximately 2" long therefore high water cutoff/alarm will occur at that level.

d. There must be a minimum 1/4" (6.4mm) clearance

between the probe and any grounding surface inside the boiler or pipe.

Option B a. The Remote Sensor can be installed directly into the

1" fittings of the boiler’s equalizing piping.

b. If installed in the upright or vertical position:

• The probe of the RS-1-BR-1 Remote Sensor will need to be cut to appropriate length based upon the level where high water cutoff/alarm is desired.

• The probe of the RS-1-LP Remote Sensor is approximately 2" long therefore high water cutoff/alarm will occur at that level.

c. If installed in the sideways or horizontal position:

• The probe of the RS-1-BR-1 Remote Sensor cannot exceed 4" in length.

NOTE: The Remote Sensors SHOULD NOT be installed in equalizing piping that is smaller than 1" NPT.

d. There must be a minimum 1/4" (6.4mm) clearance

between the probe and any grounding surface inside the boiler or pipe.

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