Lennox MPGA 050 B3, Application Manual

SERVICING THE FURNACE

ELECTRICAL SHOCK, FIRE OR EXPLOSION
HAZARD

Failure to follow safety warnings exactly could result
in dangerous operation, serious injury, death or
property damage.

Improper servicing could result in dangerous
operation, serious injury, death or property damage.

•

Before servicing, disconnect all electrical
power to furnace.

•

Wehn servicing controls, label all wires
prior to disconnecting. Reconnect wires
correctly.

•

Verify proper operation after servicing.

The ability to properly perform maintenance on this
equipment requires certain mechanical skills and
tools. If you are at all uncertain, contact your
dealer for qualified maintenance and service since
improper service could lead to furnace shutdown or
a hazardous condition which could lead to an
unsafe condition and bodily harm.

Combustion  Component  Check:

The heat exchanger, gas burners and venting system

must be checked each year, prior to the heating season,
by a qualified dealer/serviceman.

The following procedures should be performed:

 
 1. Remove the burner/manifold assembly from the

furnace, follow the instructions found on this page.

 2. Place the burner/manifold assembly on a flat work

area and vacuum the burners. It might be necessary
to use a soft bristly brush to remove dirt and then
vacuum.

 3. Disconnect wiring to combustion blower.
 4. Disconnect wiring to pressure switch, and remove

pressure switch.

 5. Remove the burner opening inlet plate and the flue

collector box with the combustion blower attached.
This will expose both the burner and flue openings of
the primary heat exchangers.

 6. Vacuum the length of each heat exchanger tube

using a straight attachment into the burner openings
and the flue openings.

 7. Replace the flue collector box, burner opening inlet

plate, and burner/manifold assembly. Insure that all
gaskets are properly positioned and that no leaks
exist.

 8. Reattach all wiring and piping as per the wiring

diagram and installation instructions.

 9. Turn on utilities and check for leaks using soapy

water and a brush.

10. A visual check of the main burner should be made at

the beginning of each heating season. 

11. Check the input rate and adjust if necessary.
12. Perform a safety check of the limit control and

pressure switch.

13. Check the air filter, clean and/or replace as

necessary.

14. Replace the appropriate access panels or door.

Never use an open flame when testing for gas
leaks! Use of an open flame could lead to a fire or
explosion!

Many soaps used for leak testing are corrosive to
certain metals. Piping must be rinsed thoroughly
with clean water after leak check has been
completed.

Manifold (or Burner/Manifold) Removal/Replacement:

1.

Make sure that all utilities (gas and electricity) are
turned off upstream of the furnace.

2.

Remove the louvered access door by sliding the door
straight up, swinging the bottom of the door away
from the furnace, and pulling the door down and out
of the furnace (See Figure 17).

3.

Disconnect the gas line from the gas valve. Be sure
that a wiring diagram is available, or be ready to
mark any wires that are disconnected. Unplug the
three connectors from the gas valve.

Figure 17

FURNACE PANEL REMOVAL

20541501

Issue 0240

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