Install Instructions

ManualsBrandsMcdonnell & Miller ManualsHeating SuppliesRB-122E, GuardDog Electronic, 120V Low Water Cut-Off - (Water)

B-122-E

OPERATION

The Model RB-122-E Low Water Cut-Off is specifically designed

to provide burner cut-off if there is an unsafe water loss, which

can result from a broken or leaking radiator or pipe, or a

cracked section in the boiler.

Model RB-122-E

Conductance Type

Low Water Cut-Offs

For Residential Hot Water Boilers

• Before using 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 HVAC 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, the boiler must be cooled to 80˚F (27˚C) and the pressure must

be 0 psi (0 bar) before servicing.

• To prevent dry fire, which could cause a fire, there must be a 2" (51mm) minimum

width in the boiler section or 14" (32mm) pipe inner diameter for probe installation and

operation.

• The probe control must be connected in series with all other boiler operating and

safety controls.

• 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

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 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).

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

WARNING

CAUTION

WARNING

Requires 120 VAC power supply and can switch 120 VAC

or 24 VAC burner control circuits

McDonnell & Miller

Installation & Maintenance

Instructions

MM-238(H)

Summary of content (8 pages)

PAGE 1
McDonnell & Miller Installation & Maintenance Instructions MM-238(H) Model RB-122-E Conductance Type Low Water Cut-Offs ® RB-122-E For Residential Hot Water Boilers Requires 120 VAC power supply and can switch 120 VAC or 24 VAC burner control circuits OPERATION The Model RB-122-E Low Water Cut-Off is specifically designed to provide burner cut-off if there is an unsafe water loss, which can result from a broken or leaking radiator or pipe, or a cracked section in the boiler.
PAGE 2
SPECIFICATIONS Features: - Automatic reset after power outage - Test button to verify operation - Short probe for installation in 1-1/4" or larger pipe - Self-cleaning probe Temperature: Storage: -40˚F to 120˚F (-40˚C to 49˚C) Ambient: 32˚F to 120˚F (0˚C to 49˚C) Humidity: 85% (non-condensing) Maximum Water Pressure: 160 psi (11 kg/cm2) Maximum Water Temperature: 250˚F (121˚C) Electrical Contact Ratings Voltage 120 VAC 240 VAC Pump Circuit Rating (Amperes) Full Load Locked Rotor 5.8 34.8 2.9 17.
PAGE 3
STEP 2 - Installation of the Low Water Cut-Off Based on the following criteria locate a suitable position for the probe (A): 1. Make sure that the end and sides of the probe are at least 1/4" (6.4 mm) from all internal metal surfaces to prevent shorting of the probe to ground. 2. Make sure that the probe extends into the boiler cavity in order to sense the water. 3. The probe (A) must be installed above the minimum safe water level (B) as determined by the boiler manufacturer. A a.
PAGE 4
STEP 3 - Electrical Installation ! WARNING • 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.
PAGE 5
(Follow the procedure below or on page 6, as appropriate for your application) Option 1: This diagram can be used if you are wiring the RB-122-E to interrupt ALL power to the boiler when a low water condition occurs. The control can be wired this way if the total amp load of the boiler does not exceed 5.8 amps @ 120 VAC when the boiler is running. If the total amp load exceeds 5.8 amps @ 120 VAC when the boiler is running, the control should be wired as shown in Option 2.
PAGE 6
Option 2: This diagram can be used if you are wiring the RB-122-E to interrupt power to the boiler burner or safety circuit only. The control can be wired this way to interrupt either a 24 VAC or 120 VAC burner control safety circuit. Consult boiler manufacturers wiring diagrams to identify the safety circuit and recommended location to connect the Yellow wires. • Connect White (N) wire as shown to 120VAC circuit neutral wire.
PAGE 7
STEP 4 - Testing Start-Up a. Before filling the system, turn on the electric power to the boiler. The low water cut-off's green "Power On" LED should be illuminated. With the room thermostat set on "heat", confirm that the burner will not operate without water in the system. The low water cut-off's red LED should be illuminated. NOTE: The burner will come on briefly (1 second or less) and then shut off to verify proper operation. ON OFF b. Fill the system with water.
PAGE 8
McDonnell & Miller MAINTENANCE SCHEDULE: • • • • Test the low water cut-off annually or more frequently. Remove and inspect the self-cleaning probe every 5 years. Replace probe every 10 years. Replace the low water cut-off every 15 years. TROUBLESHOOTING Refer to Step 2 on page 3. Problem: 1. Failure to Operate a. Cause: No voltage is being supplied to the probe control. c. Test: Using a voltage meter, verify that voltage is being sent to wire (H) and (N) of the probe control.