Xylem MM 209D Series 6667 Replacement Mechanism - Manual (Page 4)

Xylem Inc.
8200 N. Austin Avenue
Morton Grove, Illinois 60053
Phone: (847) 966-3700
Fax: (847) 965-8379
www.xyleminc.com/brands/mcdonnellmiller
McDonnell & Miller is a trademark of Xylem Inc. or one of its subsidiaries.
© 2012 Xylem Inc. MM-209D April 2012 Part No. 246776
MAINTENANCE
SCHEDULE:
• Blow down weekly during heating season.
(On 61, 67, 767, 70 and 70B). Blow down
weekly if operating pressure is 15 psi or lower.
Blow down daily if operating pressure is 15 psi
or higher.
• Follow ASME Boiler and Pressure Vessel
Code - Section VI Paragraph 7.07G. It states
that the controls should be dismantled annually
by qualified personnel, to the extent necessary
to insure freedom from obstructions and proper
functioning of the working parts.
• Check for leaks at the gasket surfaces and
solder joints. Repair or replace components as
needed.
• Check all wiring for brittle or worn insulation.
• Replace control every 10 years.
Problem:
1. Control does not turn burner off on low water.
a.
Cause: Build up of scale and sediment.
Test: Dismantle control and check for any
build up or any other obstructions that
would prevent the control from turning
off the burner. Don’t forget to check the
corrugations of the bellows.
Solution: Clean or replace as necessary.
b.
Cause: Terminals 1 and 2 on the No. 11 switch
are not opening up on low water.
Test: With a continuity meter or ohm meter
check if terminals 1 and 2 open on low
water. If they do not open, take the switch
off the control and work it manually.
Solution: If terminals 1 and 2 do not open when
operated manually, replace the switch. If
they do open see item
a. above.
Problem:
2. Control does not turn electric feeder off.
a.
Cause: Build up of scale between the corruga-
tions of the bellows. On 69 units the float
shield could be tipped down.
Test: Dismantle the control and check for
scale build up between the bellow corru-
gations. On the 69 series control check
the float shield to make sure it is in the
proper position.
Solution: Clean or replace as necessary. On 69
series reposition the float shield.
TROUBLESHOOTING