PROBLEM 5: BURNERS LIGHT WITH HEATING DEMAND BUT UNIT SHUTS DOWN

PREMATURELY (CONT.)

Condition

Possible Cause

Corrective Action/Comments

 

 

 

5.3

 

ACTION 1 − Check that the manifold pressure

− Combustion air inducer energizes

 

matches value listed on nameplate. See installa-

 

tion instructions for proper procedure.

with a heating demand.

5.3.1

ACTION 2 − Verify that the installed orifice size

− Burners light.

Unit is firing above 100% of the

match the size listed on the nameplate or installa-

− Roll−out switch trips during the

tion instructions.

nameplate input.

ACTION 3 − Check gas valve sensing hose to in-

heating demand.

 

sure no leaks are present.

− Diagnostic lights flash roll−out fail-

 

ACTION 4 − Check the input rate to verify rate

ure.

 

matches value listed on nameplate.

 

5.3.2

ACTION 1 − Tighten orifice until leak is sealed.

 

NOTE: Be careful not to strip orifice threads.

 

 

LED#1−On

Gas orifices leak at the manifold

ACTION 2 − Check for gas leakage at the

threaded orifice connection. Use approved meth-

LED#2−Slow Flash

connection.

od for leak detection (see unit instructions).

 

 

 

 

 

 

5.3.3

ACTION 1 − Check for air leakage at all joints in

 

Air leakage at the connections

the heat exchanger assembly. Condition will

 

cause high CO2 with high CO.

 

between the primary heat exchanger,

 

ACTION 2 − Seal leakage if possible, replace

 

secondary heat exchanger, and

heat exchanger if necessary, tag and return heat

 

combustion air blower.

exchanger to proper Lennox personnel.

 

 

 

 

5.3.4

ACTION 1 − Check for sooting deposits or other

 

Insufficient flow through the heat

restrictions in the heat exchanger assembly.

 

Clean assembly as outlined in instruction manu-

 

exchanger caused by a sooted or

 

al.

 

restricted heat exchanger.

ACTION 2 − Check for proper combustion.

 

 

 

 

5.3.5

ACTION 1 − Check that the burners are firing into

 

 

 

Burners are not properly located in

the center of the heat exchanger openings. Cor-

 

the burner box.

rect the location of the burners if necessary.

 

 

 

 

 

5.4

5.4.1

 

− Combustion air inducer energizes

ACTION 1 − Check for proper flow of exhaust

Recirculation of flue gases. This

gases away from intake vent. Remove any ob-

with a heating demand.

stacles in front of the intake and exhaust vent

− Burners light roughly and the unit

condition causes rough ignitions and

which would cause recirculation.

fails to stay lit.

operation. Problem is characterized

ACTION 2 − Check for correct intake and exhaust

− Diagnostic lights flash watchguard

by nuisance flame failures.

vent installation. See instructions

 

flame failure.

 

 

 

5.4.2

ACTION 1 − Remove burner and inspect the

LED#1−Alternating Slow Flash

cross−overs for burrs, or any restriction or if

Improper burner cross−overs

crossover is warped. Remove restriction or re-

LED#2−Alternating Slow Flash

place burners.

 

 

 

 

Page 52

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Image 52
Lennox International Inc G61MP Combustion air inducer energizes, Burners light Unit is firing above 100%, Nameplate input
Page 51 Page 53

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