Install Instructions

ManualsBrandsMcdonnell & Miller ManualsHeating Supplies94-7B, Combo Low Water Cut-Off & Pump Controller w/ No. 7B Switch

Series 93/193 and Series 94/194

Low Water Cut-Off/Pump Controllers

For Steam Boilers and Level Control Applications

Typical Applications:

– Primary or secondary pump controller/

low water fuel cut-off

for steam boilers

– Motorized valve controller

– Proportional valve controller

– Low water cut-off

– High water cut-off

– Alarm actuation

• 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, instal-

lation, 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 exceed the switch contact rating.

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

WARNING

Series 93 or Series 94

Series 193 or Series 194

McDonnell & Miller

Installation & Maintenance

Instructions

MM-404(H)

Summary of content (12 pages)

PAGE 1
McDonnell & Miller ® Series 93/193 and Series 94/194 Low Water Cut-Off/Pump Controllers Installation & Maintenance Instructions MM-404(H) For Steam Boilers and Level Control Applications Typical Applications: – Primary or secondary pump controller/ low water fuel cut-off for steam boilers – Motorized valve controller – Proportional valve controller – Low water cut-off – High water cut-off – Alarm actuation Series 93 or Series 94 Series 193 or Series 194 ! WARNING CAUT WARN ING ION • Before using t
PAGE 2
OPERATION Maximum Pressure: Series 93/193: 150 psi (10.5 kg/cm2) Series 94/194: 250 psi (17.6kg/cm2) Electrical Ratings Models with 7B or 7B-M Switch Models with 5 or 5-M Switch Voltage 120 VAC Switch Ratings Pump and Burner Switch Contact Ratings Pilot Duty Only Burner 120 VAC 345 VA 240 VAC Valve 345 VA 0 - 135 ohms @ 24 VAC 240 VAC Switch Settings Values are ± 1/8 ” (3mm) Models with 7B or 7B-M Switches Approximate Distance Above Cast Line In.
PAGE 3
INSTALLATION – TOOLS NEEDED: Two (2) pipe wrenches, one (1) flathead screw driver, and pipe thread dope. IMPORTANT: Follow the boiler manufacturer's instructions along with all applicable codes and ordinances for piping, blow-down valve, water gauge glass, tri-cock and electrical requirements.
PAGE 4
STEP 2 - Installing the Low Water Cut-Off/Pump Controller For Series 93/193 or 94/194 (except 94-A, 193-D and 193-G Models) a. Mount and pipe the control (A) on vertical equalizing pipes (B) at the required elevation as determined in Step 1. Install a full-ported blow-down valve (C) directly below the lower cross. B A NOTE: 1” (25mm) NPT tappings are provided on Series 93/193 controls. 1 1/4” (32mm) NPT tappings are provided for Series 94/194 controls and 193-B Model. C For 94-A and 193-G Models a.
PAGE 5
STEP 3 - Removing Float Blocking Plugs and Dowels ! CAUTION The plug and rod must be reinstalled before control is shipped installed on the boiler, and removed after boiler is placed and installed. Failure to follow this caution may damage the float and operating mechanism. a. Using a pipe wrench, remove the float blocking plugs (I) and dowels (H) from the control as shown below. b. Using a pipe wrench, screw the pipe plugs provided with control into the open tappings.
PAGE 6
STEP 4 - Installing a Water Gauge Glass and Tri-Cocks NOTE: A separate water column for installation of gauge glass and tri-cocks may be required for boilers with a Series 93 or Series 94 control. Follow the manufacturer’s instructions to install the water column. a. Determine pipe size of tri-cock and sight glass tappings for the control being installed including center distance of sight glass tappings.
PAGE 7
STEP 5 - Electrical Wiring 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 8
Low Water Cut-Off Only LOW WATER CUT-OFF CIRCUIT BLUE RED 1 2 LINE NO. 5 SWITCH BURNER STARTER Pump Control Only PUMP CONTROL CIRCUIT BLUE RED 4 3 LINE NO. 5 SWITCH PUMP STARTER Low Water Alarm Only ALARM CIRCUIT BLUE RED 3 4 NO. 5 SWITCH ALARM TRANS.
PAGE 9
For Series 93/193 or 94/194 with 7B or 7B-M Red terminals 1 and 2 are the burner circuit contacts, terminals 3 and 4 are the low level alarm circuit contacts. Blue terminal 3 is the common contact, terminals 1 and 4 are the output contacts.
PAGE 10
Wiring Connections a. Remove two screws (A) and lift off switch cover. A SWITCH COVER b. Connect BX armored cable or Thinwall electrical metal tubing to the integral fitting hub. Connect wires to terminals following appropriate wiring diagram from pages 8 and 9 for your application. NOTE: Follow local codes and standards when selecting the types of electrical fittings and conduit to connect to control. c. Replace switch cover and fasten with two screws (A).
PAGE 11
STEP 6 - Testing TROUBLESHOOTING – Dimensions shown are typical. – The following testing procedure is only meant to serve as a verification of proper operating sequence. Erratic operation of the control is the most common symptom that occurs. Erratic operation can be defined as pump and/or burner switches not switching at proper levels. Refer to the following list of items to check if the control is not operating properly. 1. Float Ball is Crushed Crushed floats are typically caused by improper blowdown.
PAGE 12
MAINTENANCE SCHEDULE: Blow down control as follows when boiler is in operation. • Daily if operating pressure is above 15 psi. • Weekly if operating pressure is below 15 psi. NOTE More frequent blow-down may be necessary due to dirty boiler water and/or local codes. • Remove head assembly and inspect water side components annually. Replace head assembly if any of the internal components are worn, corroded or damaged or if control no longer operates properly.