Service Manual

SYSTEM OPERATION

Venting

The venting system should be planned and installed with

the following in mind;

• Should not be longer than necessary

• Use 45°elbows rather than 90° elbows when possible

• Must not sag or otherwise trap condensate

• Use longest radius fittings possible

• If using 3" venting, make the transition from 2" to 3"

as close as practically possible

• Make sure there is no flue gas recirculation into the

combustion air pipe

Condensate Drainage

Furnace combustion can be affected if a furnace is holding

condensate. Check for proper connections of drain hoses,

make sure furnace condensate trap is clean. Make sure

furnace is not improperly sloped. Make sure air condition-

ing coil drain is not interfering with furnace drain.

Other Causes

1. Manifold Gas Pressure must be set for the gas being

used, Natural or L.P., high and low firing rates. If con-

verted to L.P. gas, check size of all orifices

2. Remove Draft Inducer, Check the integrity of the gasket

between the inducer and the collector box cover, any air

leak here will have a negative effect on combustion.

Check the orifice hole in the collector box, it must be

free of burrs on both sides

3. Make sure burners are clean, not out of position and line

up correctly with exchanger tubes, including the heat

exchanger orifice plate between the burners and the heat

exchanger tubes, make sure it is not loose, missing a

screw or hanging down between the burners and heat

exchangers causing flame impingement.

4. Make sure the field installed gas line is not binding and

causing distortion of burner assembly

5. If the furnace is installed as a one pipe system; make

sure the surrounding area and structure are adequate

to provide combustion air

6. Make sure there are no cabinet air leaks allowing sup-

ply air to affect combustion

7. If heat exchanger integrity is uncertain, follow proce-

dures in Service Bulletin SF-041

ComfortNet™ System