Carrier Infinity 48XT A Series Installation Instructions Manual page 25

Table 5 – Altitude Derate Multiplier for U.S.A.*
Altitude ft (m) Percent of Derate
0- - 2000
(0- - 610)
2001- - 3000*
8- -12
(610- - 914)
3001- - 4000
12- -16
(915- - 1219)
4001- - 5000
16- -20
(1220- - 1524)
5001- - 6000
20- -24
(1524- - 1829)
6001- - 7000
24- -28
(1829- - 2134)
7001- - 8000
28- -32
(2134- - 2438)
8001- - 9000
32- -36
(2139- - 2743)
9001- - 10,000
36- -40
(2744- - 3048)
* In Canada see Canadian Altitude Adjustment
{Derate multiplier factors are based on midpoint altitude for altitude range.
b. When the gas supply being used has a different heating
value or specific gravity, refer to national and local
codes, or contact your distributor to determine the
required orifice size.
2. Adjust manifold pressure to obtain low stage input rate (See
Fig. 20).
a. Turn off gas supply to unit.
b. Remove pipe plug on manifold (See Fig. 21) and
connect manometer. Turn on gas supply to unit.
c. Turn gas valve switch to ON.
d. Set unit to run for 20 minutes in low- -stage gas heat
operation using the "INSTALLER CHECKOUT" menu
on the UI.
e. Remove regulator adjustment cap from low stage gas
valve pressure regulator (See Fig. 20) and turn
low- -stage adjusting screw (3/16 or smaller flat- -tipped
screwdriver) counterclockwise (out) to decrease rate and
clockwise (in) to increase input rate.
ON/OFF SWITCH
INLET
PRESSURE TAP
Fig. 20 - - Redundant Automatic Gas Control Valve
NOTE: DO NOT set low stage manifold pressure less than 1.4 in
wc or more than 2.0 in wc for natural gas. If manifold pressure is
outside this range, change main burner orifices.
f. Re- -install low stage regulator adjustment cap.
g. Leave manometer connected.
NOTE: If orifice hole appears damaged or it is suspected to have
been re- -drilled, check orifice hole with a numbered drill bit of the
correct size. Never re- -drill an orifice. A burr- -free and squarely
aligned orifice hole is essential for proper flame characteristics.
All manuals and user guides at all-guides.com
Derate Multiplier
Factor{
0 1.00
0.90
0.86
0.82
0.78
0.74
0.70
0.66
0.62
REGULATOR COVER SCREW
PLASTIC ADJUST SCREW
REGULATOR SPRING
HIGH STAGE GAS
PRESSURE REGULATOR
ADJUSTMENT
LOW STAGE
GAS PRESSURE
REGULATOR ADJUSTMENT
MANIFOLD
PRESSURE TAP
A04167
3. Verify natural gas low stage input rate.
a. Turn off all other gas appliances and pilots served by
the gas meter.
b. If unit is not running, set unit to run for 20 minutes in
low- -stage gas heat operation using the "INSTALLER
CHECKOUT" menu on the User Interface.
c. Record number of seconds for gas meter to complete
one revolution.
d. Divide number of seconds in step c. into 3600 (number
of seconds in 1 hour).
e. Multiply result of step d. by the number of cubic feet
shown for one revolution of test dial to obtain cubic feet
of gas flow per hour.
f. Multiply result of step f. by Btu heating value of the gas
to obtain total measured input shown in Table 3.
(Consult the local gas supplier if the heating value of
gas is not known).
EXAMPLE: Assume a 90,000 high stage input unit is being
installed. Assume that the size of the dial is 2 cubic ft., one
revolution takes 129 sec., and the heating value of the gas is 1025
Btu/ft3. Proceed as follows:
a. 129 sec. to complete one revolution
b. 3600/129 = 27.9
c. 27.9 x 2 = 55.8 ft3 of gas flow/hr.
d. 55.8 x 1050 = 58,590 Btuh input.
In this example, the nominal input rate for low stage is 58,500
Btu/hr, so the low stage manifold pressure is correctly set.
If the measured low stage rate is too low, increase the manifold
pressure to increase rate. If the measured low stage rate is too high,
decrease the manifold pressure to decrease rate.
NOTE: Double- -check that UI is running on low stage gas heat
while clocking the low stage firing rate.
4. Verify proper low stage gas heat temperature rise.
a. Furnace must operate within rise range listed on rating
plate.
b. Select "COMFORT" or "EFFICIENCY" mode on User
Interface. "COMFORT" mode will provide a warmer
supply air temperature, while "EFFICIENCY" will
provide lower gas consumption.
c. Make sure access panel is re- -installed on the unit.
d. Measure supply and return temperatures as close to the
unit as possible. Subtract the return temperature from
the supply temperature to determine rise. Rise should
fall within the range specified on the rating plate.
5. Adjust manifold pressure to obtain high stage input rate
(See Fig. 20).
a. Set unit to run for 20 minutes in high- -stage gas heat
operation using the "INSTALLER CHECKOUT" menu
on the UI.
b. Remove regulator adjustment cap from high stage gas
valve pressure regulator (See Fig.20) and turn
high- -stage adjusting screw (3/16 or smaller flat- -tipped
screwdriver) counterclockwise (out) to decrease rate and
clockwise (in) to increase input rate.
NOTE: DO NOT set high stage manifold pressure less than 3.2 in
wc or more than 3.8 in wc for natural gas. If manifold pressure is
outside this range, change main burner orifices.
c. Re- -install high stage regulator adjustment cap.
d. Leave manometer connected.
6. Verify natural gas high stage input rate.
a. Turn off all other gas appliances and pilots served by
the gas meter.
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