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Gauge Glass Mounted

Directly into Boiler

CUT-OFF
LEVEL

1" BLOW DOWN

VALVE

For Boilers with

Independent Water Columns

1" STEAM

EQUALIZING PIPE

MODEL 63
LOW WATER
CUT-OFF

1" WATER

EQUALIZING PIPE

1" WATER

EQUALIZING PIPE

1" WATER

EQUALIZING PIPE

CUT-OFF
LEVEL

MODEL 63
LOW WATER
CUT-OFF

2

a.

Whether the gauge glass is mounted directly into the boiler or on an independent water column, the 
cut-off line on the 63 body casting should be mounted 1/2” (15mm) above the lowest visible point of the 
gauge glass.

a.

Locate the gauge glass and 
determine the level that the 63 
has to be mounted at in order 
to achieve the criteria in Step 1.

b.

Pipe the 63 following the 
diagrams shown to the right.
Follow the diagram that 
represents your boiler.

c.

Crosses should be used at 
each right angle connection for 
inspection and cleaning.

d.

Make sure the blow-down 
valves are full port.

e.

While the burner is operating, 
open the blow-down valve, 
causing the water level to drop in 
the float chamber while burner is 
operating. As the float drops the 
alarm circuit (if used) closes first;
then on further drop the cut-off 
circuit will open, shutting the 
burner off.

f.

Test the Model 63 before leaving 
the site.

STEP 2 - Installation of the Model 63

Model 63 – For Steam Boilers with 1” (25mm) Equalizing Lines

INSTALLATION –

TOOLS NEEDED:

One (1) flathead screwdriver and two (2) pipe wrenches.

STEP 1 - Determine the Location of the Low Water Cut-Off

For 63 models with float block

CUT  OFF

LEVEL

A

Using pipe wrench

• Remove float blocking plug (A) from low 

water cut-off body tapping.

• Screw 3/4” NPT steel plug (provided) in 

tapping.

Summary of Contents for McDonnell & Miller 63 Series

Page 1: ...INSTRUCTION MANUAL MM 206H 246746...

Page 2: ...the diagram that represents your boiler c Crosses should be used at each right angle connection for inspection and cleaning d Make sure the blow down valves are full port e While the burner is operati...

Page 3: ...riser going to the radiation or to the compression tank IMPORTANT The horizontal equalizing pipe should be below the horizontal run going to the radiation If it is not an air pocket will be created a...

Page 4: ...te the installation as described in the low water cut off installation instructions 6 After all piping assembly has been completed refill the system with water turn on all electrical supply and bring...

Page 5: ...N C C N O N C C Neutral 120 V A C Supply Hot Low Water Alarm Burner Circuit Line Load SCHEMATIC OF SWITCH OPERATION Water Level Normal Burner On Alarm Off Low Water Alarm Terminals Low Water Cut Off T...

Page 6: ...k 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 verify proper switch operation Solution Replace...

Page 7: ...es no longer operate properly If you choose to replace the switch es order the proper McDonnell Miller replacement switch or switch assembly and follow the Repair Procedure provided More frequent blo...

Page 8: ...ngs and other wear parts or consumables all of which are not warranted except as otherwise provided in the quotation or sales form will be free from defects in material and workmanship for a period of...

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