Carrier 58MXA 170 Series Installation, Start-Up, And Operating Instructions Manual page 42

NOTE: If TEST/TWIN and C
longer than 2 sec, LED will flash rapidly and ignore component
test request.
Component test sequence is as follows:
a. LED will display previous status code 4 times.
b. Inducer motor starts and continues to run until Step g of
component test sequence.
c. After 7 seconds the hot surface igniter is energized for 15
sec., then off.
d. Blower motor operates on Continuous-FAN speed for 10
sec.
e. Blower motor operates on HEAT speed for 10 sec.
f. Blower motor operates on COOL speed for 10 sec.
g. Inducer motor stops.
5. Reconnect R lead to furnace control, remove tape from blower
door switch, and re-install blower door.
6. Operate furnace per instruction on outer door.
7. Verify furnace shut down by lowering thermostat setting
below room temperature.
8. Verify that furnace restarts by raising thermostat setting above
room temperature.
Step 5—Adjustments
SET GAS INPUT RATE
Furnace gas input rate on rating plate is for installations at altitudes
up to 2000 ft.
In the U.S.A., the input ratings for altitudes above 2000 ft must be
reduced by 2 percent for each 1000 ft above sea level.
In Canada, the input ratings must be derated by 5 percent for
altitudes between 2001 ft to 4500 ft above sea level.
Furnace input rate must be within ± 2 percent of input on furnace
rating plate adjusted for altitude.
1. Determine natural gas orifice size and manifold pressure for
correct input.
a. Obtain average gas heat value (at installed altitude) from
local gas supplier.
b. Obtain average gas specific gravity from local gas supplier.
c. Verify furnace model and size. Table 9 can only be used for
model 58MXA furnaces with rating plate heating inputs
(1000's Btuh) of 040 through 120. Table 10 can only be
used for model 58MXA furnaces with a heating size of 140.
d. Find installation altitude in Table 9 or 10.
NOTE: For Canadian altitudes of 2001 to 4500 ft, use U.S.A.
altitudes of 2001 to 3000 ft in Table 9 or 10.
e. Find closest natural gas heat value and specific gravity in
Table 9 or 10.
f. Follow heat value and specific gravity lines to point of
intersection to find orifice size and manifold pressure
settings for proper operation.
-24v terminals are jumpered
OM
EXAMPLE: (0-2000 ft altitude using Table 9)
Heating value = 1050 Btu/cu ft
Specific gravity = 0.62
Therefore: Orifice No. 45 and
Manifold pressure 3.6-in. wc
* Furnace is shipped with No. 45 orifices. In this
example all main burner orifices are the correct size
and do not need to be changed to obtain the proper
input rate.
Check and verify burner orifice size in furnace. NEVER ASSUME
ORIFICE SIZE; ALWAYS CHECK AND VERIFY.
2. Adjust manifold pressure to obtain input rate.
NOTE: Manifold pressure must always be measured with burner
enclosure front REMOVED. Gas meter must always be clocked
with burner enclosure front INSTALLED.
ON/OFF SWITCH
INLET
PRESSURE TAP
Fig. 57—Redundant Automatic Gas Control Valve
a. Remove burner enclosure front.
b. Remove seal cap that conceals adjustment screw for gas
valve regulator. (See Fig. 57.)
c. Jumper R and W thermostat connections on control to start
furnace.
d. Turn adjusting screw, counterclockwise (out) to decrease
manifold pressure or clockwise (in) to increase manifold
pressure.
NOTE: This furnace has been approved for a manifold pressure
of 3.2 in. wc to 3.8 in. wc when installed at altitudes up to 2000 ft.
For altitudes above 2000 ft, the manifold pressure can be adjusted
from 2.0 in. wc to 3.8 in. wc. If manifold pressure is outside this
range, change burner orifices to obtain pressure in this range.
42
REGULATOR
SEAL CAP
REGULATOR
ADJUSTMENT
SCREW
REGULATOR SPRING
(PROPANE - WHITE, 6 TURNS
NATURAL - SILVER, 10 TURNS)
GAS PRESSURE
REGULATOR
ADJUSTMENT
MANIFOLD
PRESSURE TAP
A03142