Carrier 58MVP Installation, Start-Up, And Operating Instructions Manual page 35

Fig. 44—Inducer Housing Drain Tube
a. Obtain average yearly heat value for local gas supply.
b. Obtain average yearly specific gravity for local gas supply.
c. Verify the furnace model. Table 11 can only be used for
model 58MVP Furnaces.
d. Find natural gas heat value and specific gravity in Table 11.
e. Follow heat value line and specific gravity line to point of
intersection to find orifice size and manifold pressure
settings for proper operation at given natural gas condition.
EXAMPLE:
Heat value = 1010 Btu/cu ft
Specific gravity = 0.62
Therefore: Orifice No. 44* with manifold pressure 3.3-in.
wc for high heat and 1.4-in. wc for low heat.
* Furnace is shipped with No. 45 orifices. In this example
all main burner orifices must be changed and the manifold
pressure adjusted.
f. Check and verify orifice size in furnace. NEVER ASSUME
THE ORIFICE SIZE; ALWAYS CHECK AND VERIFY.
g. Proceed to item 3 to adjust manifold pressure.
h. Check input rate by clocking meter as described in item 2.
2. Determine natural gas input rate by clocking gas meter and
adjusting manifold pressure per item 3.
NOTE: Be sure all pressure tubing, combustion-air and vent
pipes, and burner enclosure front are in place when checking input
by clocking the gas meter.
a. Obtain average yearly heat value for local gas supply.
A94208
Fig. 45—Filling Condensate Trap
NOTE: Be sure heating value of gas used for calculations is
correct for your altitude. Consult local gas utility for altitude
adjustments of gas heating value.
b. Turn off all other gas appliances and pilots.
c. Start furnace and let run for 3 minutes.
d. Measure time (in sec) for gas meter test dial to complete 1
revolution.
e. Refer to Table 12 for cubic ft of gas per hr.
f. Multiply gas rate (cu ft/hr) by heating value (Btu/cu ft).
Obtain heating value from local gas utility.
EXAMPLE: Btu heating input = Btu/cu ft X cu ft/hr
Heating value of gas = 1010 Btu/cu ft
Time for 1 revolution of 2-cu-ft dial = 72 sec
Gas rate = 100 cu ft/hr (from Table 12)
Btu heating input = 100 X 1010 = 101,000 Btuh
In this example, the orifice size and manifold pressure
adjustment is within ±2 percent of the furnace input rate.
g. Measured gas input must not exceed gas input on unit
rating plate.
NOTE: High altitude—Gas input on rating plate is for altitudes
up to 2000 ft. Ratings for altitudes over 2000 ft must be 4 percent
less for each 1000 ft above sea level. To obtain the adjusted
altitude rating, adjust the manifold pressure (see item 3) and
replace the main burner orifices as needed. Refer to NFGC
Appendix F, Table F-4 for proper orifice sizing at high altitudes.
NOTE: In Canada, from 2000 to 4500 ft above sea level, derate
the unit 10 percent from the Conversion Station.
35
A94209