SYSTEM OPERATION
19
•
Furnace operates; integrated control module monitors
safety circuits continuously.
•
R and W thermostat contacts open, completing the call
for heat.
•
Gas valve closes, extinguishing flame.
•
Induced draft blower is de-energized following a thirty
second post purge.
•
Circulator blower continues running for selected heat off
delay period factory set at 120 seconds. If required this
can be changed in the field.
•
Electronic air cleaner is de-energized.
•
Furnace awaits the next call from thermostat.
Cooling Mode
The normal operational sequence in cooling mode is as
follows:
•
R, Y and G thermostat contacts close, initiating a call
for cool.
•
Integrated control module performs safety circuit checks.
•
Outdoor fan and compressor are energized.
•
Circulator blower is energized on cool speed following a
fixed six second on delay. If required this can be changed
in the field to 45 seconds. Electronic air cleaner terminal
is energized with circulator blower.
•
Furnace circulator blower and outdoor cooling unit
run, integrated control module monitors safety circuits
continuously.
•
R, Y and G thermostat contacts open, completing the
call for cool.
•
Outdoor fan and compressor are de-energized.
•
Circulator blower is de-energized following a fixed forty
firve second cool off delay period. Electronic air cleaner
terminal is de-energized.
•
Furnace awaits the next call from thermostat.
Fan Only Mode
The normal operational sequence in Fan Only Mode is as
follows:
•
R and G thermostat contacts close, initiating a call for
fan.
•
Integrated control module performs safety circuit checks.
•
Circulator blower is energized on low heat speed.
Electronic air cleaner terminal is energized.
•
Circulator blower runs, integrated control module
monitors safety circuits continuously.
Combustion Quality
Combustion quality can be affected by several factors. Major
factors are venting and draining.
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 conditioning
coil drain is not interfering with furnace drain.
Other Causes
1. Manifold Gas Pressure must be set within the range stated
on the furnace rating plate.
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 the field installed gas line is not binding and
causing distortion of burner assembly
4. If the furnace is installed as a one pipe system; make
sure the surrounding area and structure are adequate
to provide combustion air
5. Make sure there are no cabinet air leaks allowing sup-
ply air to affect combustion
6. If heat exchanger integrity is uncertain, follow proce-
dures in Service Bulletin SF-041
Concentric Vent Kits (DCVK) Application
The DCVK-20 and DCVK-30 kit is designed to allow the
terminations of a direct vent furnace to be “concentrically”
vented through a wall or roof. This kit allows a single
penetration to support terminations for both the vent/flue pipe
and the combustion air intake pipe.
(DCVK) Vent Termination Clearances
1. Determine termination locations based on clearances
specified in furnace installation instructions, and following
steps as shown in Figures 1,3,6,7,8 and 9.
2. The vent termination must be located at least 12” above
ground or normally expected snow accumulation levels.
3. Do NOT terminate over public walkways. Avoid areas
where condensate may cause problems such as above
planters, patios, or adjacent to windows where steam
may cause fogging.
4. The vent termination shall be located at least 4’
horizontally from any electric meter, gas meter, regulator
and any relief equipment. These distances apply ONLY
to U.S. Installations.
