Install Instructions

ManualsBrandsMcdonnell & Miller ManualsHeating Supplies751P-MT-U-120, GuardDog Electronic Manual Reset Low Water Cutoff w/ Probe(Water)

Series 751P/ 752P

• 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,

i n s t a l l a t i o n , and maintenance of plumbing and electrical equipment and/or systems in

a c c o r dance with all applicable codes and ord i n a n c e s .

• 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 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 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.

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

WARNING

Series 751P

Series 752P

Probe Type Low Water Cut-Off

Applications:

– Primary conductance type control for

commercial or industrial hot water boilers.

– Secondary control for commercial or

industrial steam boilers.

McDonnell & Miller

Installation & Maintenance

Instructions

MM-283

Summary of content (8 pages)

PAGE 1
McDonnell & Miller Installation & Maintenance Instructions MM-283 Series 751P Series 752P Probe Type Low Water Cut-Off Applications: Series 751P/ 752P – Primary conductance type control for commercial or industrial hot water boilers. – Secondary control for commercial or industrial steam boilers. WARNING • Before using product, read and understand instructions. • Save these instructions for future reference.
PAGE 2
SPECIFICATIONS The Series 751P & Series 752P probe type LWCO's provide protection against low water conditions for commercial and industrial applications. These controls are fully CSD-1 compliant and can be used as the primary LWCO on hot water boilers and as the secondary LWCO (manual reset) on steam boilers. Automatic Reset Models Whenever water is below the level of the probe, the control will go into a low water condition.
PAGE 3
STEP 1 - Where to Install a. Based on the following criteria locate a suitable position for the probe (A): For all Applications: 1. Make sure probe is installed above minimum safe water line as determined by the boiler manufacturer. 2. Make sure that ends and sides of the probe are at least 1/4” (6.4mm) from all internal metal surfaces. 3. Make sure the probe is positioned to shut off the boiler before the water level falls below the lowest visible part of the gauge glass. For Steam Boilers: 1.
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b. Apply a small amount of pipe dope to the first external threads (D) of the probe (A). IMPORTANT: Do not use Teflon® tape or thread sealant. c. Using a wrench, tighten the probe (A) into the tapped connection (E) that was determined in Step 1 of these instructions. Tighten to 47 ft•lb (64 N•m). NOTE: Be sure to align the probe so that the mounting screws (F) are in a hori zontal position. d.
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a. Push out the probe knockouts and remove completely from the control housing. b. Using a flatblade screwdriver, loosen the probe mounting screws (F) 1/8" (3mm) about 1-1/2 turn s and slip the control housing (G) over these two screws at a 20˚ angle. c. Rotate the control housing (G) 20˚ counterclockwise so that the slots in the control base are firmly under the screw heads. Tighten the mounting screws (F) to approximately 2 ft•lb (2.6 N•m). d.
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STEP 5 - Electrical Wiring WARNING To prevent electrical fire or equipment damage, electrical wiring must have a rating of 167°F (75C) if the liquid's temperature exceeds 180°F (82°C). Failure to follow this warning could cause property damage, personal injury or death. IMPORTANT Boiler manufacturer schematics should always be follow e d. 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.
PAGE 7
STEP 6 - Testing and Diagnostic Procedures Series 750 LWCO with Green Power On LED and Red Low Water LED Start-Up a. Before filling the system, turn on the electric power to the boiler. 1. Upon initial power up, the Green and Red lights will flash simultaneously 4 times. 2. The Green and Red lights will turn “ON”. 3. The burner will never turn “ON” d u ring power up, If water is off the probe. b. Now fill the boiler with water. (auto reset units only) 1.
PAGE 8
McDonnell & Miller If control fails to operate, perform the following diagnostic checks. 1. Check to be sure the water level in the boiler is at or above the level of the probe. 2. Re-check all wiring to ensure proper connections as specified in boiler manufacturers wiring diagrams or these instructions. 3. Check to ensure that Teflon® tape has not been used on the threaded connection of the electrode to the boiler. 4. Re-check the electrical ground connection for the remote sensor and control unit. 5.