4. Heat pump mode
When installed with a heat pump, the furnace control auto-
matically changes the timing sequence to avoid long blower
off time during demand defrost cycles. When the W-Y or
W-Y-G thermostat inputs are received at the same time, the
control changes the blower to heating speed or starts the
blower if it was off, and begins a heating cycle. The blower
remains on until the end of the prepurge period, then shuts off
until the end of the ignition warm up and trial for ignition
periods (a total of 24 sec). The blower then comes back on at
heating speed.
When the W input signal disappears, the control begins the
normal inducer post-purge period and the blower changes to
cooling speed after a 1-sec delay. If the W-Y-G signals
disappear at the same time, the blower remains on for the
selected heating blower off delay period and the inducer goes
through its normal post-purge period. If the W-Y inputs
should disappear, leaving the G signal input, the control goes
into continuous blower and the inducer remains on for the
normal post-purge period.
Anytime the control senses false flame, the control locks out
of the heating mode. This occurs because the control cannot
sense the W input due to the false flame signal and, as a result,
sees only the Y input and goes into cooling mode blower off
delay. All other control functions remain in standard format.
NOTE:
EAC-1 terminal is energized whenever blower operates.
HUM terminal is only energized when gas valve is energized.
START-UP PROCEDURES
1. Purge gas lines—After all connections have been made, purge
the lines and check for leaks.
Never purge a gas line into a combustion chamber. Never use
matches, candles, flame, or other sources of ignition to check
for gas leakage. Use a soap-and-water solution to check for
gas leaks. Failure to follow this warning could result in fire,
explosion, personal injury, or death.
2. Component test—The furnace control allows all components,
except gas valve, to be run for a short period of time.
This feature helps diagnose a system problem in case of a
component failure. To initiate component test procedure, short
(jumper) the TEST 3/16-in. quick connect terminal on control
(adjacent to diagnostic light) and the C
OM
-24V terminal on
furnace thermostat connection block for approximately 2 sec.
(See Fig. 14.)
NOTE:
Component test feature will not operate if any thermostat
signal is present at control.
Component test sequence is as follows.
a. Momentarily jumper TEST and C
OM
-24V terminals until
LED goes off.
b. LED will display previous status 4 times.
c. Inducer motor starts and continues to run for entire com-
ponent test.
d. Hot surface igniter is energized for 15 sec, then de-
energized.
e. Blower motor operates on cooling speed for 10 sec, then
stops.
f. Blower motor operates on heating speed for 10 sec, then
stops.
g. Inducer motor stops.
3. To operate furnace, follow procedures on operating instruction
label attached to furnace.
4. With furnace operating, set thermostat below room tempera-
ture and observe that furnace goes off. Set thermostat above
room temperature and observe that furnace restarts.
ADJUSTMENTS
1. Set gas input rate
Furnace gas input rate on rating plate is for installations at
altitudes up to 2000 ft. Furnace input rate must be within
±
2
percent of input on furnace rating plate.
a. Determine natural gas orifice size and manifold pressure
for correct input.
(1.) Obtain average yearly gas heat value (at installed
altitude) from local gas supplier.
(2.) Obtain average yearly gas specific gravity from local
gas supplier.
(3.) Verify furnace model. Table 8 can only be used for
model 58RAV Furnaces.
(4.) Find installation altitude in Table 8.
NOTE:
For Canada altitudes of 2000 to 4500 ft, use U.S.A.
altitudes of 2001 to 3000 ft in Table 8.
(5.) Find closest natural gas heat value and specific gravity
in Table 8.
(6.) Follow heat value and specific gravity lines to point of
intersection to find orifice size and manifold pressure
settings for proper operation .
EXAMPLE: (0—2000 ft altitude)
Heating value = 1050 Btu/cu ft
Specific gravity = 0.62
Therefore: Orifice No. 43*
Manifold pressure 3.6-in. wc
* Furnace is shipped with No. 43 orifices. In this example
all main burner orifices are the correct size and do not need
to be changed to obtain proper input rate.
(7.) Check and verify burner orifice size in furnace.
NEVER
ASSUME
ORIFICE
SIZE.
ALWAYS
CHECK AND VERIFY.
b. Adjust manifold pressure to obtain input rate.
(1.) Remove regulator adjustment seal cap. (See Fig. 17.)
(2.) Turn adjusting screw, counterclockwise (out) to de-
crease manifold pressure or clockwise (in) to increase
manifold pressure.
Table 7—Altitude Derate Multiplier for U.S.A.
ALTITUDE
(FT)
% OF
DERATE
DERATE MULTIPLIER
FACTOR FOR U.S.A*
0—2000
0
1.00
2001—3000
8—12
0.90
3001—4000
12—16
0.86
4001—5000
16—20
0.82
5001—6000
20—24
0.78
6001—7000
24—28
0.74
7001—8000
28—32
0.70
8001—9000
32—36
0.66
9001—10,000
36—40
0.62
* Derate multiplier factor is based on midpoint altitude for altitude range.
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