Mcdonnell & miller – Xylem MM 273E Model 750-HW-MT-120 Probe Type High Water Manual Reset Control Unit User Manual

Page 8

Troubleshooting

MAINTENANCE

SCHEDULE:

• Inspect probe annually or more frequently for scale build-up and clean or replace if necessary.

Make certain there is no scale or build-up on the probe or its white PTFE insulator. Be careful not to damage
the PTFE insulator.

• Replace probe every 10 years. More frequent replacement of the probe is required if it is used in locales

where significant water treatment is required, or in applications with high make-up water requirements.

• Replace the control unit every 15 years.

If control fails to operate as required, perform the following diagnostic checks:

1. Check to be sure that the water level in the boiler is below the probe.

2. Re-check all wiring to ensure proper connections as specified in boiler manufacturer’s wiring diagrams

or these instructions.

3. Check to ensure that PTFE tape has not been used on the threaded base of the remote sensor

the boiler.

4. Re-check the electrical ground connection for the remote sensor and control unit.

Replace Probe if:
• PTFE insulator is cracked or worn.
• Probe is loose.
Failure to follow this caution could cause property damage, personal injury or death.

CAUTION

Clean probe by wiping with non-abrasive cloth and rinsing with clean water. DO NOT
use sharp instruments to remove any accumulations of rust or scale.

NOTE

McDonnell & Miller

Xylem Inc.
8200 N. Austin Avenue
Morton Grove, Illinois 60053
Phone: (847) 966-3700
Fax: (847) 965-8379
www.mcdonnellmiller.com

2013

Part No. 210564

E December