Xylem MM 251C User Manual

Series 750B-C3 Chamber

with 3 Probes

Series 750B-C4 Chamber

with 4 Probes

Features

• Cast Iron Body

• Sight Glass Tappings

• Gage Cock Tappings

• Stainless Steel Probes

• NEMA 4X Electrical Enclosure

• 250 psi Maximum Working Pressure

Designed for use with the Series 750B remote
mount control module to make a complete system
for level control in a boiler or other vessel.

INSTRUCTION MANUAL

MM-251C

Remote Chamber

WARNING

!

• Before using this product read and understand instructions.

TION

U

CA

G

IN

RN

A

W

• Save these instructions for future reference.

• All work must be performed by qualified personnel trained in the proper application,
installation, 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 the limit and
operating controls, before leaving the site.

• 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.

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 follow this warning could cause property damage, personal inj ury 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.

&

'

4-3/16"
(106.4)

4-3/8"

(111)

A

B

C

D

2-1/2"
(63.5)

3-1/4"
(82.5)

3-1/4"
(82.5)

3-1/8"
(79.4)

1" NPT

11-1/2"

(292)

18-5/8"

(473)

1/2" NPT

1/2" NPT

1/2" NPT

CONDUIT

CONNECTION

1"
NPT

1" NPT

1/2" NPT

ELECTRODE

PRE-CUT

9" PROBE ROD

CUT AS

NEEDED

SPECIFICATIONS

Maximum Water Temperature: 406˚F (208˚C)
Maximum Water Pressure: 250 psi (17.6 kg/cm
Maximum Steam Pressure: 250 psi (17.6 kg/cm

All probes are cut to 9" length (229mm). Any of these probes can
be used as the low water cut-off level probe. The remaining
probes can be ‘cut to length’ in the field using a metal cutting saw
to achieve desired pump control or additional alarm activation.

C3 C4

No. of 3 4

Probes

AXX

BXX

CXX

DX

2

)

2

)

INSTALLATION –

TOOLS NEEDED:

One (1) pipe wrench, one (1) flathead screwdriver and/or 11/32" nut driver,
one (1) metal-cutting saw, and pipe sealing compound.

2