Lennox G21 V SERIES User manual

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G21V SERIES UNITS
GAS UNITS
503,226M
7/97
Supersedes 7/96
7$%/( 2) &217(176
UNIT DIMENSIONS 2................................
PARTS ARRANGEMENT 3...........................
G21V TYPICAL INSTALLATION 4.....................
REQUIREMENTS 5..................................
GENERAL 6.........................................
INSTALLATION--Setting and Leveling Equipment 6.....
RETURN AIR OPENING GUIDELINES 6................
FILTER ASSEMBLY AND FILTERS 7...................
DUCT SYSTEM 7....................................
EXHAUST, INTAKE & CONDENSATE PIPING 7.........
GAS PIPING 15......................................
ELECTRICAL 16.....................................
UNIT START--UP 18..................................
GAS PRESSURE ADJUSTMENT 19...................
HIGH ALTITUDE INFORMATION 19...................
OTHER UNIT ADJUSTMENTS 19.....................
ELECTRONIC IGNITION 19...........................
VSP2--1 BLOWER CONTROL BOARD 19...............
BLOWER SPEED AND ADJUSTMENT 20..............
VSP2--1 OPERATION 23..............................
SERVICE 24.........................................
REPAIR PARTS LIST 25..............................
START--UP AND PERFORMANCE CHECK LIST 26......
G21V TROUBLESHOOTING 26.......................
WHAT TO DO IF YOU SMELL GAS:
If the information in this manual is not
followed exactly, a fire or explosion
may result causing property damage,
personal injury or loss of life.
WARNING
Do not store or use gasoline or other
flammable vapors and liquids in the
vicinity of this or any other appliance.
Installation and service must be per-
formed by a qualified installer, service
agency or the gas supplier.
-Do not try to light any appliance.
-Do not touch any electrical switch; do not
use any phone in your building.
-Immediately call your gas supplier from a
neighbors phone. Follow the gas suppliers
instructions.
-If you cannot reach your gas supplier, call
the fire department.
-Extinguish any open flames.
Litho U.S.A.

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INTAKE PIPE 2
(51mm) PVC
EXHAUST PIPE
2(51mm) PVC
GAS
CONNECTOR
CONTROL
ACCESS PANEL
BLOWER
COMPARTMENT
ACCESS PANEL
RETURN
AIR
SUPPLY AIR
CONDENSATE DRIP LEG
ISOLATION PADS (ISOMODE) (4)
MANUAL
MAIN SHUT OFF
VALVE
DRIP LEG
FLEXIBLE BOOT IN PLENUM
OR DUCT (SUPPLY AIR)
RETURN AIR PLENUM DUCT LINING
1.5 TO 3 LB. (24 TO 48 kg) DENSITY,
MATTE FACE, 1 (25mm)
THICK INSULATION INSULATED
PAST FIRST ELBOW
SUPPLY AIR PLENUM
1.5 TO 3 LB. (24 TO 48 kg) DENSITY,
MATTE FACE, 1 (25mm) THICK IN-
SULATION INSULATED PAST FIRST
ELBOW
ELECTRICAL CONDUIT:
IF CLAMPED TO UNIT
IT MUST BE ISOLATED
FROM DUCT WORK AND
JOISTS
FLEXIBLE BOOT IN DUCT OR PLENUM (SUPPLY AIR)
FLEXIBLE BOOT IN
DUCT OR PLENUM
(RETURN AIR)
FLEXIBLE BOOT IN PLENUM
OR DUCT (RETURN AIR)
MUFFLER**
MUFFLER**
**All G21-80/100 units require the use of at least one muffler in the exhaust pipe and one in the intake pipe. Mufflers are recommended
options on all other units.
*Installation procedures outlined inthis manual are presentedas recommendation only and donot supersede or replace local orstate
code. If local or state codes do not exist, the procedures outlined in this manual are recommended only and do not constitute code.
(Gas connector may be used for Ca-
nadian installation if acceptable by
local authority having jurisdiction.)
NOTE--Many of the specific installation recommendations such as insulated plenums, flexible boots and isolation hangers are strongly
suggested to control vibration and to ensure acceptable sound levels in the conditioned space. The recommendations should be used
as a guideline when installing the system. Specific installation methods, duct construction and insulation methods may vary and are
acceptable provided the methods provide the same objective, are industry accepted and meet code requirements.
FLEXIBLE ISOLATION
HANGER
GAS SUPPLY PIPING
CENTERED IN INLET
HOLE (SLOT)

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All G21 units are A.G.A. (American Gas Association)
and C.G.A (Canadian Gas Association) certified.
Installation of Lennox gas central furnaces must con-
form with local building codes or, in the absence of local
codes, with the current National Fuel Gas Code (ANSI--
Z223.1). The National Fuel Gas Code is available from :
American National Standards Institute, Inc.
1430 Broadway
New York, NY 10018
The installation of Lennox high efficiency gas furnaces
must conform with the current Installation Code for
Gas Burning Appliances and Equipment CAN/CGA--
B149.1-- (natural gas) or CAN/CGA--B149.2-- (propane
gas) and/or local codes. For unspecified requirements
the installation must conform with the manufacturers
C.G.A. certified instructions contained herein.
The electrical installation must conform with the Cana-
dian Electrical Code Part 1, C.S.A. C22.1, and/or local
codes.
The plumbing installation must comply with local
plumbing or waste water codes where applicable.
The furnace is certified for installation clearances to
combustible material as listed on the appliance rating
plate and table 1.
Clearances Location Inches (mm)
Service access
To combustible
materials
Front
Top
36 (914)
1 (25)
6 (152)
*Appliance shall not be installed directly on carpeting, tile or oth-
er combustible material other than wood flooring.
NOTE--Service access clearance must be maintained.
TABLE 1
Exhaust side
Exhaust 0
(from side of unit)
Side, rear and front 0
Floor 0*
Appliance shall not be installed directly on carpeting, tile
or other combustible material other than wood flooring.
Accessibility and service clearances must take prece-
dence over fire protection clearances.
For installation in a residential garage, unit must be lo-
cated or protected to avoid physical damage by ve-
hicles. Unit must be adjusted to obtain a temperature
rise and external static pressure within the range speci-
fied on appliance rating plate.
G21V units must be installed so that electrical compo-
nents are protected from water.
When this furnace is used in conjunction with cooling
units, it shall be installed in parallel with or on the up-
stream side of the cooling units to avoid condensation
in the heating element. With a parallel flow arrange-
ment, damper (or other means to control flow of air)
shall be adequate to prevent chilled air from entering
furnace and, if manually operated, must be equipped
with means to prevent operation of either unit unless
damper is in full heat or cool position.
When installed, furnace must be electrically grounded
in accordance with current National Electric Code,
ANSI/NFPA No. 70 in the U.S. and with current CSA
C22.1 Canadian Electrical Code Part 1 in Canada, if an
external electrical source is utilized. The National Elec-
tric Code is available from:
National Fire Protection Association
470 Atlantic Avenue
Boston, MA 02210
Wiring to be done in the field, between the furnace and
devices not attached to the furnace or between sepa-
rate devices which are field--installed and located, shall
conform with the temperature limitation for typeTwire
[63 E F (17 E C) rise] when installed in accordance with
these instructions.
When a furnace is installed so that supply ducts carry air
circulated by the furnace to areas outside the space con-
taining the furnace, the return air shall also be handled
by a duct(s) sealed to the furnace casing and terminat-
ing outside the space containing the furnace.
WARNING
Product contains fiberglass wool.
Disturbing the insulation in this product during in-
stallation, maintenance, or repair will expose you
to fiberglass wool dust. Breathing this may cause
lung cancer. (Fiberglass wool is known to the
State of California to cause cancer.)
Fiberglass wool may also cause respiratory, skin,
and eye irritation.
To reduce exposure to this substance or for further
information, consult material safety data sheets
available from address shown below, or contact
your supervisor.
Lennox Industries Inc.
P.O. Box 799900
Dallas, TX 75379--9900
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A -- Shipping Damage
Check unit carefully for shipping damage. Receiving
party should contact last carrier immediately if any
shipping damage is found.
NOTE -- Special care should be taken to check the align-
ment of thegas piping atthe point itpenetrates the ves-
tibule panel. Inspect the rubber grommet for damage;
there must be no direct contact between the gas pipe
and the vestibule panel.
B -- Shipping and Packing List
1 -- Assembled G21V furnace
1 -- Filter
1 -- Filter rack
1 -- Bag assembly containing:
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C -- Shipping Bolt Removal
Remove four heat section shipping bolts from bottom
side of blower deck before starting unit. Access bolts
through blower compartment.
WARNING
Improper installation, adjustment, alteration, ser-
vice or maintenance can cause property damage,
personal injury or loss of life. Installation and ser-
vice must be performed by a qualified installer,
service agency or the gas supplier.
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When unit is installed where freezing temperatures are
possible, condensate trap and condensate line must be
protected by a grounded and sheathed self--regulating
heating cable and insulation. Condensate trap must be
accessible for servicing and unit must be level to ensure
proper drainage from coil. Heating cable kit is available
from Lennox in various lengths; 6 ft. (1.8m) -- kit no.
18K48; 24 ft. (7.3m) -- kit no. 18K49; and 50 ft. (15.2m) --
kit no. 18K50. Heat cable kit may also be used on ex-
haust vent pipe and terminations to keep moisture
from freezing.
1 -- Holes are provided in the corners of unit base for
leveling unit. Install leveling bolts (if desired as
shown, or shim under unit. See figure 2.
CAUTION
If leveling bolts are used, install the plastic nuts as
shown and tighten snugly before setting unit.
CABINET
SIDE
AFTER UNIT IS
LEVEL, TIGHTEN THIS NUT
UNIT BASE
LEVEL UNIT
WITH THIS NUT
INSTALL PLASTIC
NUTS WITH FLAT
SIDE TOWARD BASE .LEVELING BOLT
LEVELING BOLT INSTALLATION
FIGURE 2
2 -- Set unit in desired location keeping in mind clear-
ances listed on unit rating plate. Keep in mind gas
supply connection, electrical supply, vent connec-
tions and clearances for installing and servicing unit.
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Return air can be brought in either side or bottom of
unit. Scribe lines show the outline of each return air
opening. Remove remaining insulation from around
return air opening. See figure 3.
FIGURE 3
G21V UNIT
RETURN AIR
PLENUM
ISOLATION
PADS
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NOTE -- Insulation adhesive is only used inside of
scribe lines.
NOTE -- Units with V5 blowers use larger opening.
1 -- Cut opening in floor or platform.
2 -- Flange return air plenum and lower into opening.
3 -- Place glass fiber insulation strips around opening.
Position isolation mounting pads at corners of in-
sulation. Insulation should not overlap mounting
pads. Trim away any excess insulation from strips.
4 -- Set unit. Make sure unit is sitting on isolation pads.
NOTE -- Be careful not to damage glass fiber insula-
tion. Check for tight seal.

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G21V series unit is equipped with a reusable foam filter.
Filter must be in place any time unit is in operation. The
filter clips are required for bottom return. Install filter
mounting clips, provided, and secure with sheet metal
screws. If side return air is required, filter clips can be
used to mount the filter inside the unit or the provided
external filter kit can be used.
1 -- Turn off electrical power to unit.
2 -- Using the mounting frame and figure 4 as a guide,
cut an opening in the unit.
3 -- Secure filter rack to unit using four existing outside
screws on blower deck and base of unit. Secure duct
to flange on filter rack using sheet metal screws.
4 -- Slide filter in rack from the front.
5 -- Restore electrical power to unit and check unit for
proper operation.
FIGURE 4
EXTERNAL SIDE RETURN FILTER RACK FOR G21V
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1 -- Install flexible canvas boots or equivalent on both
supply and return air plenums. Boots should be
placed as close as possible to unit.
2 -- Insulate supply air plenum and duct system at least
through the first elbow. Use 1--1/2 to 3 lb. (24 to 48
kg) density, matt face, 1 (25mm) thick insulation.
Provisions must be made to keep insulation in place
and to protect edges from airflow deterioration.
3 -- Size and install supply and return system using in-
dustry--approved standards that result in a quiet
and low--static system with uniform distribution.
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A--Exhaust and Intake Piping Requirements
For U.S. installation, venting requirements must comply
with the current AGA/GAMA standards. For Canadian
installation, the venting system must comply with cur-
rent ULC standard for type BH gas vents No. S636. Fur-
nace shall not be connected to any type B, BW or L vent
or vent connector and shall not be connected to any
portion of a factory built or masonry chimney.
Two mufflers (one each in the exhaust and intake piping)
are required and furnished for use with the G21--80/100
units. See table 2 for optional usage of mufflers with G21
units. Mufflers should be located and installed as di-
rected in instructions packaged with muffler kit.
IMPORTANT
Exhaust piping muffler(s) installed horizontally in
unconditioned spaces must be protected by self--
regulating heating cable and insulation.
TABLE 2
MODEL NO. EXHAUST MUFFLER INTAKE MUFFLER
G21V--60 1 (optional) 1 (optional)
G21V--80/100 1 (required)
2 (additional option)
1 (required)
2 (additional option)
All PVC pipe, fittings, primer and solvent cement must
conform with American National Standard Institute and
the American Society for Testing and Materials (ANSI/
ASTM)standards.Refertotable3forapprovedpiping
and fitting materials. The solvent shall be free flowing
and contain no lumps, undissolved particles or any for-
eign matter that adversely affects the joint strength or
chemical resistance of the cement. The cement shall
show no gelation, stratification, or separation that can-
not be removed by stirring.
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CAUTION
Solvent cements for plastic pipe are flammable
liquids and should be kept away from all sources
of ignition. Do not use excessive amounts of sol-
vent cement when making joints. Good ventila-
tion should be maintained to reduce fire hazard
and to minimize breathing of solvent vapors.
Avoid contact of cement with skin and eyes.
Primers and solvents must meet ASTM specifications.
PVC primer is specified in ASTM F 656. Use PVC solvent
cement as specified in ASTM D 2564. Low temperature
solvent cement is recommended. Metal, plastic strap-
ping or large wire ties may be used for vent pipe hangers.

3DJH 
PVC pipe used for exhaust and intake lines should be
sized per table 4. Note that maximum length of vent
pipe is for one run; either intake or exhaust. Maximum
vent length given is not the total length of intake + ex-
haust vents.
3
(76mm)
2--1/2
(64mm)
2--1/2
(64mm)
2--1/2
(64mm) 3
(76mm) 3 (76mm) 3 (76mm)
3
(76mm) 3 (76mm) 3 (76mm)
TABLE 4
MINIMUM DIAMETER FOR G21 VENTING
Number of 90 E Elbows
Linear Pipe
Len gth
(Max. Feet) 02468
5
(1.5m)
10
(3m)
20
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(12.2m)
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(15.2m)
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(18.3m)
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(21.3m)
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(24.4m)
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(27.4m)
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2--1/2
(64mm)
Each 90 E elbow is equivalent to 5 ft. (1.52m) of vent
pipe. Two 45 E elbows are equivalent to one 90 E elbow.
One 45 E elbow is equal to 2.5 feet (.75M) of vent pipe.
If intake and exhaust piping runs are notequalin length
and combination, the larger diameter pipe (as sized per
table 4) must be used for both runs. Regardless of the
diameter of pipe used, the standard roof and wall ter-
minations described in section D--Intake and Exhaust
Piping Terminations should be used. Exhaust piping
must terminate with 1--1/2 (38mm) pipe.
Muffler lengths should be excluded when measuring
vent pipe runs for sizing. Vent pipe must be sized at 2
(51mm) between unit and mufflers.
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1-- Measure and cut PVC pipe to desired length.
2-- Debur and chamfer end of pipe, removing any
ridges or rough edges. If end is not chamfered,
edge of pipe may remove cement from fitting
socket and result in a leaking joint.
3-- Clean and dry surfaces to be joined.
4-- Test fit joint and mark depth of fitting on outside of
pipe.
5-- Uniformly apply liberal coat of primer to inside
socket surface of fitting and male end of pipe to
depth of fitting socket.
6-- Promptly apply solvent cement to end of pipe and
inside socket surface of fitting. Cement should be
applied lightly but uniformly to inside of socket.
Take care to keep excess cement out of socket. Ap-
ply second coat to end of pipe.
IMPORTANT--Time is critical at this stage. Do not
allow primer to dry before applying cement.
7-- Immediately after applying last coat of cement to
pipe, and while both inside socket surface and end
of pipe are wet with cement, forcefully insert end
of pipe into socket until it bottoms out. Turn pipe
1/4 turn during assembly (but not afterpipe is fully
inserted) to distribute cement evenly.
NOTE--Assembly should be completed within 20
seconds after last application of cement. Hammer
blows should not be used when inserting pipe.
8-- After assembly, wipe excess cement from pipe at
end of fitting socket. A properly made joint will
show a bead around its entire perimeter. Any gaps
may indicate a defective assembly due to insuffi-
cient solvent.
9-- Handle joints carefully until completely set.
B--Exhaust a nd Condensate Piping
This unit is designed for either right or left side exit of
exhaust piping.
NOTEIf unit is equipped with a V5 blower and side re-
turn air is used, it is recommended that the exhaust
piping drip leg be routed out of the side opposite the
return air duct. This should be done to avoid interfer-
ence between the drip leg and the return air duct. The
drip leg may be installed on the return air side provided
it clears the duct.
1-- Cut PVC pipe (provided) to the desired length for
exit from the unit.
2-- Slide PVC pipe through rubber grommet in cabi-
net. Care must be taken to center pipe in hole.
3-- Compression elbow is mounted for left side ex-
haust pipe exit on G21V--60/80 units and right side
exit on G21V--100 units. If piping must exit on other
side, disconnect exhaust pressure tubing, rotate
and tighten compression elbow and reconnect
tubing.
NOTEDifferential pressure switch will not oper-
ate properly if tubing is kinked.
4-- Cement PVC pipe to compression elbow which is
already in place.
NOTECare must be taken to assure a secure,
tight seal between compression elbow assembly
and manifold outlet.
5-- Cement drip leg assembly tee to PVC pipe as
shown in figure 5.

3DJH 
FIGURE 5
COMPRESSION
ELBOW
(Factory Installed)
EXHAUST PIPING
(Field--provided)
STAND PIPE
(Must be left open.)
CONDENSATE
CONNECTION
(Rotate to proper
drain position before
cementing.)
DRIP LEG ASSEMBLY
PVC PIPE
(Cut to correct
length for exit
from unit.)
DRIP LEG
ASSEMBLY TEE
RUBBER BOOT
WITH HOSE CLAMP
(Loosen clamp and remove
to facilitate cleanout)
6 -- Make sure rubber clean--out boot is securely fas-
tened to drip leg by hose clamp. Rotate condensate
connection to suitable drain position and cement
drip leg subassembly to drip leg assembly tee.
IMPORTANT -- Debris may buildup in bottom of drip leg
and prevent proper drainage. Leave enough clearance
below drip leg to remove clean-out boot for future
maintenance.
IMPORTANT -- Stand pipe must remain open at the top
to vent drain. Open end of pipe must not be used to
connect drain hoses or other condensate hoses.
7 -- Cement exhaust pipe into top of drip leg assembly
tee and route to outside of structure using exhaust
and intake piping requirements listed in section A.
All horizontal runs of exhaust pipe must slope back
toward unit. A minimum of 1/4 (6mm) drop for
each 12 (305mm) of horizontal run is mandatory
for drainage. Horizontal runs of exhaust piping
must be supported every 5 ft. (1.52m) using isola-
tion hangers.
NOTE -- Exhaust piping must be insulated with 1/2
(13mm) Armaflex or equivalent when run through un-
heated space. Do not leave any area of exhaust pipe
open to outside air; exterior exhaust must be insulated
with 1/2 (13mm) Armaflex or equivalent.
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8 -- Connect condensate drain line (1/2 [13mm] SDR
11 plastic pipe or tubing) to condensate connec-
tion on drip leg assembly and route to open drain.
Condensate line must be sloped downward away
from drip leg to drain. If drain level is above drip
leg, condensate pump must be used to conden-
sate line. Condensate drain line should be routed
within the conditioned space to avoid freezing of
condensate and blockage of drain line. If this is not
possible, a heat cable kit may be used on the con-
densate drip leg and line. Heating cable kit is avail-
able from Lennox in various lengths; 6ft. (1.8m) --
kit no. 18K48; 24ft. (7.3m) -- kit no. 18K49; and 50ft.
(15.2m) -- kit no. 18K50.
CAUTION
Do not use copper tubing or existing copper con-
densate lines for drain line.
9 -- Seal unused exhaust line piping hole in cabinet
with snap--plug provided.
CAUTION
The exhaust vent pipe operates under positive
pressure and must be completely sealed to pre-
vent leakage of combustion products into the liv-
ing space.
C--Intake Piping
1 -- Cement intake piping in slip connector located at
top of unit.
2 -- Determine intake piping size using table 4.
3 -- Suspend piping at a minimum of every 5 ft.
(1.52m) using isolation hangers. A suitable hang-
er can be fabricated by putting a sleeve of Arma-
flex refrigeration piping insulation around the pipe
and suspending it using metal strapping as shown
in figure 6. Place a small sheet metal strip between
the Armaflex and the metal strapping to prevent
crimping. Do not secure piping directly to joist or
flooring.
4 -- In areas where piping penetrates joists or interior
walls, hole must be large enough to allow clear-
ance on all sides of pipe through center of hole us-
ing an isolation hanger.
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3DJH 
5-- Route piping to outside of structure. Continue
with installation following instructions given in ex-
haust and intake piping termination section.
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D--Removal of Unit from Common Venting System
If a G21V furnace replaces a furnace which was com-
monly vented with another gas appliance, the size of
the existing vent pipe for that gas appliance must be
checked. Without the heat of the original furnace flue
products, the existing vent pipe is probably oversized
for the single water heater or other appliance. The vent
should be checked for proper draw with the remaining
appliance.
The following test should be conducted while all ap-
pliances (both in operation and those not in operation)
are connected to the common venting system. If the
venting system has been installed improperly, correc-
tions must be made.
1-- Seal any unused openings in the common venting
system.
2-- Visually inspect the venting system for proper size
and horizontal pitch and determine there is no
blockage or restriction, leakage, corrosion and
other deficiencies which could cause an unsafe
condition.
3-- Insofar as is practical, close all building doors and
windows and all doors between the space in which
the appliances remaining connected to the com-
mon venting system are located and other spaces
of the building. Turn on clothes dryers and any ap-
pliances not connected to the common venting
system. Turn on any exhaust fans, such as range
hoods and bathroom exhausts, so they will oper-
ate at maximum speed. Do not operate a summer
exhaust fan. Close fireplace dampers.
4-- Follow the lighting instruction. Place the appliance
being inspected in operation. Adjust thermostat
so appliance will operate continuously.
5-- Test for spillage at the draft hood relief opening af-
ter 5 minutes of main burner operation. Use the
flame of a match or candle, or smoke from a ciga-
rette, cigar or pipe.
6-- After it has been determined that each appliance
remaining connected to the common venting sys-
tem properly vents when tested as outlined above,
return doors, windows, exhaust fans, fireplace
dampers and any other gas--burning appliance to
their previous condition of use.
7-- If improper venting is observed during any of the
above tests, the common venting system must be
corrected. The common venting system should be
re--sized to approach the minimum size as deter-
mined by using the appropriate tables in appendix
G in the current standards of the National Fuel Gas
Code ANSI Z223--1 in the U.S.A., and the appropri-
ate Category 1 Natural Gas and Propane ap-
pliances venting sizing tables in the current stan-
dards of the CAN/CGA--B149.1 and .2 in the Natural
Gas and Propane Installation Code in Canada.
E--Intake and Exhaust Piping Terminations
Intake and exhaust pipes may be routed either hori-
zontallythroughanoutsidewallorverticallythrough
the roof. In attic or closet installations, vertical termi-
nation through the roof is preferred. Figures 7
through 18 show typical terminations.
CAUTION
Care must be taken to avoid recirculation of ex-
haust back into intake pipe.
1-- Use PVC pipe for both intake and exhaust piping
2-- Secure all joints, including drain leg, gas tight us-
ing approved PVC solvent.
3-- Piping diameters should be determined according
to length of pipe run. See table4. Locate intake pip-
ing upwind (prevailing wind) from exhaust piping.
To avoid re--circulation of exhaust gas on roof ter-
minations, end of exhaust pipe must be higher
than intake pipe.
Exhaust and intake exits must be in same pressure
zone. Do not exit one through the roof and one on
the side. Also, do not exit the intake on one side
and the exhaust on another side of the house or
structure.

3DJH 
4-- Intake and exhaust pipes should be placed as close
together as possible at termination end (refer to il-
lustrations). Maximum separation is 3 (76mm)
on roof terminations and 6 (152mm) on side wall
terminations.
5-- Exhaust piping must terminate straight out or up
as shown. On roof terminations, the intake piping
should terminate straight down using two 90 E el-
bows (See figure 7). In rooftop applications, a 2 X
1--1/2 (51mm x 38mm) reducer must be used on
the exhaust piping at the point where it exits the
structure to improve the velocity of exhaust away
from the intake piping.
FIGURE 7
ROOF TERMINATION KIT
(15F75) LB--49107CC for 2 (50.8) Venting
(44J41) LB--65678A for 3 (76.2) Venting
UNCONDITIONED
ATTIC SPACE
1/2 (12.7) FOAM
INSULATION IN
UNCONDITIONED
SPACE
3 x 2 (76.2 x 50.8) OR
2 x 1--1/2 (50.8 x 38.1)
PVC REDUCER
3(76.2) MAX.
12 (304.8) ABOVE
AVERAGE SNOW
ACCUMULATION
3 (76.2) OR
2 (50.8) PVC
PROVIDE SUPPORT
FOR INTAKE AND
EXHAUST LINES
8 (203.2) MIN
Inches(mm)
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NOTE--If winter design temperature is below 32 E F(0 E C),
exhaust piping must be insulated with 1/2 (13mm), Ar-
maflex or equivalent when run through unheated space.
Do not leave any surface area of exhaust pipe open to
outside air; exterior exhaust pipe must be insulated with
1/2 (13mm) Armaflex or equivalent. In extreme cold cli-
mate areas, 3/4 (19mm) Armaflex or equivalent is rec-
ommended. Insulation on outside runs of exhaust pipe
must be painted or wrapped to protect insulation from
deterioration.
NOTE--During extremely cold temperatures, below
approximately 20 E F (6.67 E C), units with long runs of
vent pipe through unconditioned space, even when in-
sulated, may form ice in the exhaust termination that
prevents the unit from operating properly. Longer run
times of at least 5 minutes will alleviate most icing
problems. A low ambient thermostat kit (70G49) can be
installed to increase run times. Also, a heating cable
may be installed on exhaust piping and termination to
prevent freeze--ups. Heating cable installation kit is
available from Lennox. See Exhaust and Condensate
Piping section for part numbers.
NOTE--Care must be taken to avoid re--circulation
of exhaust back into intake pipe.
6-- On field supplied terminations on side wall exits,
exhaust piping should extend a maximum of 12
(305mm) beyond the outside wall. Intake piping
should be as short as possible. See figure 8.
7-- On field supplied terminations a minimum separa-
tion distance between the end of the exhaust pipe
and the end of the intake pipe is 8 (203mm).
8-- If intake and exhaust piping must be run up a side
wall to position above snow accumulation or other
obstructions. Piping must be supported every 3 ft.
(.91m) as shown in figure 6. Refer to figures 12 and
13 for proper piping method. WTK wall termina-
tion kit must be extended for use in this applica-
tion. See figure 16 or use kit WTKX shown in figure
17. When exhaust and intake piping must be run
up an outside wall, the exhaust piping is reduced
to 1--1/2 (38mm) after the final elbow. The intake
piping may be equipped with a 90 E elbow turn-
down. Using turndown will add 5ft. (1.52m) to the
equivalent length of the pipe.
),*85( 
1/2 (13) ARMAFLEX
INSULATION IN
UNCONDITIONED SPACE
2 (51) PVC 1--1/2 (38) PVC
12 (305) MIN.
2 X 1--1/2
(51 x 38)
PVC REDUCER
1/2 (13) ARMAFLEX
INSULATION
6 (152)
MAXIMUM
2 (51) PVC
COUPLING
8 (203)
MINIMUM
OUTSIDE
WALL
Inches (mm)
TOP VIEW
WALL RING KIT
(15J74) LB--49107CB for 2 (50.8) Venting

3DJH 
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TOP VIEW
WALL TERMINATION
(22G44) LB--49107CD for 2 (50.8) Venting
(44J40) LB--65701A for 3 (76.2) Venting
Inches(mm)
OUTSIDE WALL
1/2 (12.7) FOAM INSULATION
IN UNCONDITIONED SPACE
Optional Turndown
Shown
(Intake Only)
),*85( 
12 (305) ABOVE
AVERAGE SNOW
ACCUMULATION
EXHAUST
EXHAUST
TERMINATION
INTAKE
TERMINATION
INTAKE
Inches (mm)
CONCENTRIC ROOFTOP TERMINATION
(60G77) LB--49107CE for 2 (50.8) Venting Only
9-- Position termination ends so they are free from
any obstructions and above the level of snow ac-
cumulation (where applicable). Termination ends
must be a minimum of 12 (305mm) above grade
level. Do not point into window wells, stairwells,
alcoves, courtyard areas or other recessed areas.
Do not position termination ends directly below
roof eaves or above a walkway. Since the G21 unit
is a certified, direct vent Category IV gas furnace,
the location of the termination is limited by local
building codes. In the Absence of local codes, refer
to the current National Fuel Gas Code Z223.1 in the
US, and the current standards CAN/CGA--B149.1
and --B149.2 of the natural gas and propane instal-
lation instructions in Canada for details. The ter-
mination should be at least 12 (305mm) from any
opening through which flue products could enter
the building.
When horizontally vented, minimum clearance for
termination from electric meters, gas meters, reg-
ulators and relief equipment is 4 ft. (1.2m) for US
installations. Refer to the current CAN/CGA--
B149.1 and --B149.2 for installations in Canada or
with authorities having local jurisdiction.
At vent termination, care must be taken to main-
tain protective coatings over building materials
(prolonged exposure to exhaust condensate can
destroy protective coatings). It is recommended
that the exhaust outlet not be located within 6 ft.
(1.82m) of a condensing unit because the conden-
sate can damage the painted coating.
IMPORTANT
Combustion air intake inlet and exhaust outlet
should not be located within 6 ft. (1.82m) of dryer
vent or combustion air inlet or outlet of another
appliance. Piping should not exit less than 3 ft.
(.91m) from opening into another building.
IMPORTANT
For Canadian Installations Only:
In accordance to CAN/CGA--B149.1 and .2, the
minimum allowed distance between the combus-
tion air intake inlet and the exhaust outlet of other
appliances shall not be less than 12 (305mm).
10-- Suspend piping at a minimum of every 5 ft. (1.52m)
using isolation hangers. A suitable hanger can be
fabricated by putting a sleeve of Armaflex refrigera-
tion piping insulation around the pipe and suspend-
ing it using metal or plastic strapping or a large wire
tie or other flexible strap to dampen the vibrations as
shown in figure 6. Place a small sheet metal strip be-
tween the Armaflex and the metal strapping to pre-
vent crimping. Do not secure piping directly to joist
or flooring.
11-- In areas where piping penetrates joists or interior
walls, hole must be large enough to allow clear-
ance on all sides of pipe through center of hole us-
ing an isolation hanger.
12-- Isolate piping at the point where itexits the outside
wall or roof. Use termination kit LB--49107C.
13-- When furnace is installed in a residence where unit
is shut down for an extended period of time, such
as a vacation home, make provisions for draining
drip leg on exhaust line.
14-- Based on the recommendation of the manufactur-
er, a multiple furnace installation may use a group
of up to four termination kits WTK assembled to-
gether horizontally, as shown in figure 15.

3DJH 
FIGURE 11
EXHAUST
EXHAUST
TERMINATION
INTAKE
TERMINATION
INTAKE 12 (305mm) Min.
above grade.
CONCENTRIC WALL TERMINATION
(60G77) LB--49107CE for 2 (50.8) Venting Only
,QFKHV PP
FIGURE 12
12 (305) ABOVE
AVERAGE S NOW
ACCUMULATION
UNCONDITIONED
SPACE
12 (305) MIN. for 2 (51)
20 (508) MAX. for 3 (76)
8 (203)
MIN.
1/2 (13) FOAM
INSULATION
1/2 (13) FOAM
INSULATION IN
UNCONDITIONED
SPACE
PROVIDE SUPPORT
FOR INTAKE AND
EXHAUST LINES EVERY
36 (914)
OUTSIDE WALL
Inches(mm)
SIDE VIEW
WALL RING TERMINATION
(15F74) LB--49107CB for 2 (51) Venting
FIGURE 13
,QFKHV PP
FRONT VIEW
WALL TERMINATION
(22G44) LB--49107CD for 2(50.8) Venting
(44J40) LB--65701A for 3(76.2) Venting
3 (76.2) OR
2 (50.8) 90 E ELBOW
1/2 (12.7)
FOAM
INSULATION
Inches(mm)
3 (76.2) OR
2 (50.8) 90 E ELBOW
3 x 2 (76.2 x 50.8) OR
2 x 1--1/2 (50.8 x 38.1)
REDUCER BUSHING LOCATION
FOR OFFSET TERMINATION
Optional Turndown
(Not Shown)
May Be Used on
Intake Only
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FIGURE 15
EXHAUST
VENT
INTAKE VENT
5--1/2
(140mm)
Front View
12
(305mm)
5
(127mm)
18 MAX.
(457mm)
EXHAUST VENT
INTAKE VENT
Side View
OPTIONAL VENT TERMINATION FOR
MULTIPLE UNIT INSTALLATION
WALL TERMINATION KIT WTK

3DJH 
FIGURE 16
12 MIN.
(305)
Above Grade
COVER EXHAUST
VENT WITH
1/2 (13)
FOAM
INSULATION
Front View
Side View
VENT TERMINATIONS
MODEL WTK WALL TERMINATION KIT (30G28)
EXTENDED VENT FOR GRADE CLEARANCE
Inches (mm)
5
(127)
5-1/2
(140)
EXHAUST
AIR
INTAKE
AIR
GRADE
12
(305)
8 (203)
Minimum
12 (305)
Minimum
ABOVE GRADE
INTAKE
AIR
EXHAUST
AIR
GRADE
FIGURE 17
VENT TERMINATIONS
MODEL WTKX (30G79)
EXTENSION RISER FOR GRADE CLEARANCE
4
(102)
8 MIN.
(203.2)
EXHAUST VENT
INTAKE
VENT
GRADE
GRADE
EXHAUST
VENT
INTAKE
VENT
34
(864)
12
(304.8)
9
(228.6)
NOTE--Enclosed exhaust pipe
is insulated with 1/2 (13mm)
foam insulation. If intake and
exhaust pipes are reversed, slit
and remove foam insulation
and reapply to other vent. Ex-
haust vent must be insulated.
Front View
Side View
OUTSIDE WALL
G21 VENTING IN EXISTING CHIMNEY
FIGURE 18
NOTE--Do not discharge exhaust gases directly
into any chimney or vent stack. If vertical dis-
charge through an existing unused chimney or
stack is required, insert piping inside chimney
until the pipe open end is above top of chimney
and terminateas illustrated. In anyexteriorpor-
tion of chimney, the exhaust vent must be insu-
lated. An alternate method is to fill the chimney
with vermiculite or equal to take advantage of
its acoustic and thermal properties.
8 -- 12
(203mm -- 305mm)
3 -- 8
(76mm--
203mm)
3 -- 8
(76mm--
203mm)

3DJH  
*$6 3,3,1*
A--Gas Supply
The unit is shipped standard for right--side installation
of gas piping. A piping hole is also fabricated in the left
side for an alternate piping arrangement.
1-- When connecting the gas supply, the length of run
from the meter, the number of fittings and furnace
rating must be considered in determining the pipe
size to avoid excessive pressure drop. Table 5 lists
recommended pipe sizes for typical applications.
A drip leg should be installed in the pipe run to the
unit. In some localities, codes may require a
manual main shut--off valve and union (furnished
by installer) installed external to unit. Union must
be of ground joint type.
A 1/8 (3.2mm) N.P.T. plugged tapping, accessi-
ble for test gauge connection, must be installed
immediately upstreamofthe gas supply connec-
tion to the furnace.
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2-- The use of one of the following gas connectors is
recommended:
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The above connectors may be used if acceptable by
the authority having jurisdiction. A gas connector is
provided and, if used, should be installed between
the manual main shut--off valve and ground joint
union. See figure 19 for correct piping.
CAUTION
Flexible gas connector must not be used to exit the
unit. Flex connector must be installed in U--shaped
fashion in order to achieve its purpose (See figure
19). Do not secure to unit ducting or structure.
3-- Center gas line through piping hole. Gas line
should not touch side of unit.
4-- Connect gas supply line.
TABLE 5
GAS PIPE CAPACITY -- FT
3
/HR (kL/HR)
Nominal Internal Length of Pipe--Feet(m)
Nominal
Iron Pipe Size
--Inches(mm)
Internal
Diameter
--Inches(mm) 10
(3.048) 20 (6.096) 30 (9.144) 40 (12.192) 50 (15.240) 60 (18.288) 70 (21.336) 80 (24.384) 90 (27.432) 100 (30.480)
1/4
(6.35) .364 (9.246) 43 (1.13) 29 (.82) 24 (.68) 20 (.57) 18 (.51) 16 (.45) 15 (.42) 14 (.40) 13 (.37) 12 (.34)
3/8
(9.53) .493 (12.522) 95 (2.69) 65 (1.84) 52 (1.47) 45 (1.27) 40 (1.13) 36 (1.02) 33 (.73) 31 (.88) 29 (.82) 27 (.76)
1/2
(12.7) .622 (17.799) 175 (4.96) 120 (3.40) 97 (2.75) 82 (2.32) 73 (2.07) 66 (1.87) 61 (1.73) 57 (1.61) 53 (1.50) 50 (1.42)
3/4
(19.05) .824 (20.930) 360 (10.19) 250 (7.08) 200 (5.66) 170 (4.81) 151 (4.28) 138 (3.91) 125 (3.54) 118 (3.34) 110 (3.11) 103 (2.92)
1
(25.4) 1.049 (26.645) 680 (919.25) 465 (13.17) 375 (10.62) 320 (9.06) 285 (8.07) 260 (7.36) 240 (6.80) 220 (6.23) 205 (5.80) 195 (5.52)
1--1/4
(31.75) 1.380 (35.052) 1400 (39.64) 950 (26.90) 770 (21.80) 660 (18.69) 580 (16.42) 530 (15.01) 490 (13.87) 460 (13.03) 430 (12.18) 400 (11.33)
1--1/2
(38.1) 1.610 (40.894) 2100 (59.46) 460 (41.34) 1180 (33.41) 990 (28.03) 900 (25.48) 810 (22.94) 750 (21.24) 690 (19.54) 650 (18.41) 620 (17.56)
2
(50.8) 2.067 (52.502) 3950 (111.85) 2750 (77.87) 2200 (62.30) 1900 (53.80) 1680 (47.57) 1520 (43.04) 1400 (39.64) 1300 (36.81) 1220 (34.55) 1150 (32.56)
2--1/2
(63.5) 2.469 (67.713) 6300 (178.39) 4350 (123.17) 3520 (99.67) 3000 (84.95 2650 (75.04) 2400 (67.96) 2250 (63.71) 2050 (58.05) 1950 (55.22) 1850 (52.38)
3
(76.2) 3.068 (77.927) 11000 (311.48) 7700 (218.03) 6250 (176.98) 5300 (150.07) 4750 (134.50) 4300 (121.76) 3900 (110.43) 3700 (104.77) 3450 (97.69) 3250 (92.03)
4
(101.6) 4.026 (102.260) 23000 (651.27) 15800 (447.39) 12800 (362.44) 10900 (308.64) 9700 (274.67) 8800 (249.18) 8100 (229.36) 7500 (212.37) 7200 (203.88) 6700 (189.72)
NOTE--Capacity given in cubic feet of gas per hour (kilo liters of gas per hour) and based on 0.60 specific gravity gas.

3DJH 
FIGURE 19
MANUAL MAIN
SHUT--OFF VALVE
GAS CONNECTOR*
GAS VALVE
GROUND JOINT
UNION
LEFT SIDE PIPING
MANUAL MAIN
SHUT--OFF VALVE
GAS CONNECTOR*
GAS VALVE
GROUND JOINT
UNION
RIGHT SIDE PIPING
(STANDARD)
1/8 (3.2mm)
N.P.T.
PLUGGED TAP
1/8
(3.2mm)N.P.T.
PLUGGED TAP
*Gas connector may be used forCanadian installation if acceptable by local authority
having jurisdiction.
B--Leak Check
After gas piping has been completed, carefully check all
piping connections (factory and field) for gas leaks. Use
a leak detecting solution or other preferred means.
CAUTION
Some soaps used for leak detection are corrosive
to certain metals. Carefully rinse piping thorough-
ly after leak test has been completed. Do not use
matches, candles, flame or other sources of igni-
tion to check for gas leaks.
IMPORTANT
The furnace must be isolated from the gas supply
piping system by closing its individual manual
shut--off valve during any pressure testing of the
gas supply piping system at test pressures equal
to or less than 1/2 psig (3.45 kPa).
The furnace and its individual shut--off valve must
be disconnected from the gas supply piping sys-
tem during any pressure testing of the system at
test pressures greater than 1/2 psig (3.45 kPa).
(/(&75,&$/
1-- Select fuse and wire size according to blower mo-
tor amps. For V5 units, the minimum circuit am-
pacity is 17.4 amps and maximum fuse or circuit
breaker size is 25 amps. For V3 units, the minimum
circuit ampacity is 12 amps and maximum fuse or
circuit breaker size is 15 amps.
2-- Access openings are provided on both sides of
cabinet to facilitate wiring.
3-- Install room thermostat according to instructions
provided with thermostat. See figure 20 for ther-
mostat designations.
4-- Install a separate fused disconnect switch near the
unit so that power can be turned off for servicing.
5-- Complete wiring connections to equipment using
provided wiring diagrams.
6-- Electrically ground unit in accordance with local
codes or, in the absence of local codes, in accor-
dance with the National Electric Code ANSI/NFPA
70 in U.S. and Canadian Electrical Code Part 1 in
Canada.
7-- Install an auxiliary receptacle near unit.
FIGURE 20
G21V and OUTDOOR UNIT
THERMOSTAT DESIGNATIONS
G21V Furnace
1ST STAGE
COMPRESSOR
COMMON
Y2 C
RW2 G CR
HS/HP UNIT
COMMON
HS/HP UNIT
COMPRESSOR
Outdoor Unit
Thermostat
W1
G
Y1
Y2
W1 Y1
TO EFFICIENCY+, HARMONYI AND II
2ND STAGE
COMPRESSOR HS/HP UNIT
COMPRESSOR
1ST STAGE HEAT
POWER
2ND STAGE HEAT
BLOWER
C
W2
R
DS
NM
(Not all connections apply. Refer to specific
thermostat, accessory and outdoor unit.)
Terminal Strip Designations Unique to G21V Units
(Figure 21)
R This signal provides 24VAC to the thermostat and,
in Harmony II zoning applications, to the control
center.
DS This is the speed regulation input that switches
the blower from LOW to HIGH speed, in cooling
mode. DS is the PWM (pulse width modulation) in-
put in zoning applications that use Harmony II zon-
ing system.
NM This terminal is used for non--zoning (Non--Har-
mony), non--modulating applications where heat
exchanger modulation is NOT desired. The heat
demand from the thermostat should be wired to
this terminal instead of W1.

3DJH 
CAUTION
Do not connect the heat demand wire to both the
W1 and the NM terminals. Damage to the unit will
occur. Use the W1 terminal for zoning (Harmony)
applications and the NM terminal for non--zoning
(Non--Harmony) applications.
W1 This terminal is used for zoning (Harmony) mod-
ulating applications where heat exchanger modu-
lation IS desired. This terminal is also used for the
first stage of a two--stage heating application.
W2 This terminal is used for two--stage heating.
Two--stage heating is not available when using the
non--modulating NM terminal.
G21V TERMINAL STRIP
FIGURE 21
W1
W2
R
3 AMP
TYPE
MDX
SLOW BLOW
G
Y2
Y1
DS
C
NM
FIGURE 22
TYPICAL G21V WIRING DIAGRAM

3DJH 
81,7 67$5783
FOR YOUR SAFETY READ BEFORE LIGHTING
WARNING
Do not use this furnace if any part has been under
water. Immediately call a qualified service techni-
cian to inspect the furnace and to replace any part
of the control system and any gas control which
has been under water.
WARNING
If overheating occurs or if gas supply fails to shut
off, shut off the manual gas valve to the appliance
before shutting off electrical supply.
CAUTION
Before attempting to perform any service or main-
tenance, turn the electrical power to unit OFF at
disconnect switch.
BEFORE LIGHTING smell all around the appliance area
for gas. Be sure to smell next to the floor because some
gas is heavier than air and will settle on the floor.
Use only your hand to push in or move the gas control
lever or switch. Never use tools. If the lever or switch
will not push in or move by hand, do not try to repair it,
call a qualified service technician. Force or attempted
repair may result in a fire or explosion.
A--Gas Valve Operation
WARNING
If you do not follow these instructions exactly, a
fire or explosion may result causing property dam-
age, personal injury or loss of life.
This unit is equipped with an automatic spark ignition
system with flame rectification. Once combustion has
started, the purge blower and spark ignitor are turned
off. Do not try to light by hand.
Gas Valve Operation for Robertshaw and White
Rodgers Valves (Figure 23)
1-- Set thermostat to lowest setting.
2-- Turn off all electrical power to furnace.
FIGURE 23
ROBERTSHAW 7200 GAS VALVE
GAS VALVE
SELECTO R ARM
IN OFF
POSITION
WHITE RODGERS
36E GAS VALVE
GAS VALVE
SHOWN
IN OFF
POSITION
3-- This appliance Is equipped with an ignition device
which automatically lights the burner. Do not try to
light the burner by hand.
4-- Remove unit access panel.
5-- On Robertshaw 7200 gas valve, depress lever on gas
control and move to OFF and release. For White
Rodgers 36E gas valves, move switch to OFF .Do
not force.
6-- Wait five (5) minutes to clear out any gas. Smell for
gas, including near the floor. If you then smell gas,
STOP! Immediately call your gas supplier from a
neighbors phone. Follow the gas suppliers in-
structions. If you do not smell gas go to next step.
7-- On Robertshaw 7200 gas valve, depress lever on
gas control and move to ON and release. For White
Rodgers 36E gas valves, move switch to ON .
8-- Replace unit access panel.
9-- Turn on all electrical power to unit.
10-- Set thermostat to desired setting.
11-- If the furnace will not operate, follow the instruc-
tions To Turn Off Gas To Unit and call your ser-
vice technician or gas supplier.
B--To Turn Off Gas To Unit
1-- Set thermostat to lowest setting.
2-- Turn off all electrical power to unit if service is to be
performed.
3-- Remove heat section access panel.
4-- On Robertshaw 7200 gas valve, depress lever on
gas control and move to OFF and release. For
White Rodgers 36E gas valves, move switch to
OFF . Do not force.
5-- Replace unit access panel.

3DJH 
*$6 35(6685( $'-8670(17
Gas Flow
To check proper gas flow to combustion chamber, de-
termine Btu input from the appliance rating plate. Di-
vide this input rating by the Btu per cubic foot of avail-
able gas. Result is the number of cubic feet per hour
required. Determine the flow of gas through gas meter
for 2 minutes and multiply by 30 to get the hourly flow
of gas to burner.
Gas Pressure
1 -- Check gas line pressure with unit firing at maxi-
mum rate. Normal natural gas inlet line pressure
should be 7.0 in. w.c. (1.74 kPa). Normal line pres-
sure for propane/LP gas is 11.0 in. w.c. (2.75 kPa).
IMPORTANT -- Minimum gas supply pressure is
listed on unit rating plate for normal input. Opera-
tion below minimum pressure may cause nuisance
lockouts.
2 -- After line pressure is checked and adjusted, check
regulator pressure. Correct manifold pressure
(unit running) is specified on nameplate. To mea-
sure, connect gauge to pressure tap in elbow be-
low expansion tank.
+,*+ $/7,78'( ,1) 250$7,21
The G21V unit is approved for altitudes of 0 to 4,500 ft. (0
to 1,372 m) above sea level in both the U.S.A. and Cana-
da. No adjustment is necessary.. Due to the self--adjust-
ing characteristics of pulse combustion, no high altitude
kits should be necessary at any altitude.
27+(5 81,7 $'-8670(176
Heat Anticipation Settings
Units with White Rodgers gas valves ---- 0.6
Units with Robertshaw gas valves ---- 0.6
Propane/LP Gas Conversion
NOTE -- G21V series units are NOT shipped with the
components required for field conversion to propane/
LP gas. A separate kit must be ordered.
Limit/Modulation Control
Limit Control ---- Factory set: No adjustment necessary.
Modulation Control ---- The modulation control is facto-
ry set to maintain supply air temperature between
70 E F (21 E C) + lower limit of rise range and 70 E F (21 E C)
+ upper limit of rise range.
Temperature Rise and External Static Pressure
Check temperature rise and external static pressure. If
necessary, adjust blower speed to maintain tempera-
ture rise and external static pressure within range
shown on unit rating plate.
Electrical
1 -- Check all wiring for loose connections.
2 -- Check fuse located on unit control box. Fuse
should be a 3 amp MDX slow blow.
3 -- Check for correct voltage at unit (unit operating).
4 -- Check amp--draw on blower motor.
Motor Nameplate __________Actual__________.
NOTE -- Do not secure electrical conduit directly to
ducting or structure.
(/(&7521,& ,*1,7,21
The ignition control has an added feature of an internal
watchguard control.
The watchguard feature within the control serves as an
automatic reset device for ignition controls locked--out
because the burner has failed to light. This type of nui-
sance lock--out is usually attributed to low gas line pres-
sure. After one hour of continuous thermostat demand
for heat, the watchguard will break and remake thermo-
stat demand to the furnace and reset the electronic igni-
tion control to relight the furnace.
963 %/2:(5 &21752/ %2$5'
G21V units are equipped with a variable speed motor
that is capable of maintaining a specified CFM through-
out the external static range. The unit uses the VSP2--1
variable speed control board which controls the blow-
er speed and provides diagnostic LEDs. The control
has both a non--adjustable, factory preset ON fan
timing delay and an adjustable OFF timing delay.
The VSP2--1 also senses limit trip condition and turns
on the blower. The G21V limit switch is located in the
middle of the vestibule wall. When excess heat is
sensed in the heat exchanger, the limit switch will
open and interrupt the current to the gas valve, while at
the same time the VSP2--1 energizes the blower on
heating speed. The limit automatically resets when the
unit temperature returns to normal and the blower is
de--energized.
Diagnostic LEDs located on the VSP2--1 control board
are provided to aid in identifying the units mode of op-
eration. Certain scenarios will arise depending on the
jumper positions. Read through the diagnostic and
jumper settings sections before adjusting blower
speed. Refer to figure 24 for identification.

3DJH 
JP2
HIGH LOW ADJUST HEAT
CFM
HI/LOW
ON/OFF
HEAT
HTG.
BLOWER
12
DS2
DS3
DS1
DS4
1
2
3
4
1
2
3
4
1
2
3
4
TEST
--
+
NORM
210
150
90
270
JP1
VSP2--1 VARIABLE SPEED CONTROL BOARD SELECTIONS
FIGURE 24
DIAGNOSTIC
DS LEDS
FAN OFF
TIMING PINS
JP2
13 PIN PLUG
(BOARD TO MOTOR)
HEATING STAGE
JUMPER SELECTOR PINS
JP1
15 PIN PLUG
(BOARD TO VARIOUS POINTS
IN FURNACE)
HIGH SPEED
SELECTOR PINS
(COOLING ONLY)
LOW SPEED
SELECTOR PINS
(COOLING AND HEATING)
HEATING SPEED
SELECTOR PINS
OPERATIONAL
SELECTOR PINS
(Affects both heating and
cooling modes)
1
1
%/2:(5 63((' $1' $'-8670(17
Diagnostic LEDs
'6 k212))l
ON/OFF --DS3 indicates there is a demand for the blow-
er motor to run. When the ON/OFF LED--DS3 is lit, a de-
mand is being sent to the motor. In heating mode only,
there is a 45 second fan ON delay in energi zing ON/
OFF LED--DS3. Light will not go off until adjustable fan
OFF delay has expired.
If ON/OFF LED--DS3 is on and both HIGH/LOW LED--
DS1 & HEAT LED--DS2 are off, the motor will operate in
low speed.
'6 k+($7l
If HEAT LED--DS2 is on, the blower is running in the
heat speed according to the HEAT jumper setting. In
heating mode only, there is a 45 second delay in ener-
gizing HEAT LED--DS2. Light will not go off until adjust-
able fan OFF delay has expired.
'6 k+,/2:l
HIGH/LOW LED--DS1 indicates whether the blower is
operating in high or low speed. When the light is off,
the blower is running in low speed according to the
LOW jumper setting. When HIGH/LOW LED--DS1 is
on, the blower is operating in high speed according to
the HIGH jumper setting.
'6 k&)0l
CFM LED--DS4 indicates the CFM the unit is operating, ac-
cording to the jumper settings. The light flashes once for
approximately every 100 CFM (47 L/s). For example, if the
unit is operating at 1000 CFM (472 L/s), CFM LED--DS4 will
flash 10 times. If the CFM is 2050 (967 L/s), CFM LED--DS4
will flash 20 full times plus one fast or half flash.
At times the light may appear to flicker or glow. This
takes place when the control is communicating with
the motor between cycles. This is normal operation.
The appropriate speed according to application and
CFM need is selected by moving jumper pins.
Jumper Settings
IMPORTANT
Before changing jumper setting, make sure the
motor has completely stopped. Any jumper set-
ting change will not take place while the motor is
running.
To change jumper positions, gently pull the jumper off
the pins and place it on the desired set of pins. The fol-
lowing section outlines the different jumper selections
available and conditions associated with each one. Re-
fer to figure 24 for identification.
After the CFM for each application has been deter-
mined, the jumper settings must be adjusted to reflect
those given in tables 7 and 8. From tables 7 and 8, de-
termine which row of CFM volumes most closely
matches the desired CFM. Once a specific row has
been chosen (+, NORMAL, or --), CFM volumes from
other rows cannot be used. Below are the descriptions
of each of the jumper selections.
Refer to table 6 for factory settings. Refer to table 8 for
the approximate air volume for each setting.
TABLE 6
MODEL
NUMBER
G21V5--80
G21V3--60
G21V5--100
G21V3--80
VSP2--1 FACTORY SETTINGS
HIGH LOW HEAT
141
241
ADJUST
NORM
NORM