Carrier 58GS - Manual (Page 10)

d. Multiply cu ft per hour times heating value of
gas (Btu/cu ft). Obtain heating value of gas
from local utility.
X heat value of gas
= gas input, Btuh
Example:
Time for one revolution of 2 eu ft dial = 72
seconds.
Heat value of gas = 1070 Btu/cu ft
3600
72
X 2 = 100 cu ft/hr
100 X 1070 = 107,000 Btuh
e. To adjust input rate, remove cap that con­
ceals regulator adjustment. Turn adjusting
screw counterclockwise (out) to decrease
input. When adjusting, DO NOT change
manifold pressure more than 0.3 in. wg. Any
major adjustment should be made by chang­
ing orifices.
2. High Altitude
Ratings are approved for altitudes to 2000 ft
for all gases. Ratings for altitudes over 2000 ft
are 4% less for each 1000 ft above sea level.
Adjust Main Burner Flame — The main burner
flame should be clear blue, almost transparent, with
a well-defined inner cone. If there is too much pri­
mary air, the flame will be well defined, but with a
tendency to float or lift off the burner ports.
1. Allow unit to operate 5 minutes.
2. When burners are equipped with primary air
adjustment, adjust each burner by closing air ad­
justment device until slight yellow tip appears on
flame; then open, just enough to clear yellow
from flame.
Temperature Rise — Determine the air tem­
perature rise as follows:
1. Place duct thermometers in return and supply
ducts as near furnace as possible. Be sure
thermometers do not “see” heat element so that
radiant heat will not affeet thermometer read­
ings. This is particularly important with straight-
run ducts.
2. When thermometers stabilize, subtract return air
temperature from supply air temperature to
determine air temperature rise.
3. Adjust air temperature rise by adjusting blower
speed. Increase blower speed to reduce tempera­
ture rise. Decrease blower speed to increase
temperature rise.
Adjustment of Blower Speed
WARN!N
changing speed, tap.
To change motor speed, remove the electric lead
from left side of Molex speed selector (see Fig. 7)
and relocate it on the desired terminal on the plug-in
terminal block/ speed selector located on the blower.
The white lead remains in the “C” (common) ter­
minal at all times. The black lead (on heat/cool
models) is used to select the proper speed for
cooling mode and the red lead is used to select the
speed for heating mode.
CAOTTON: "Whien adjasisn^ ihe blower speed,
make cefiain that the temperature rise across
the heat exchanger does not exceed that speci­
fied on the rating plate.
Table 3 — Speed Selector
SPEED TAP NO
Common C
Hi ...................... 1......................
Med-Hi 2
Med-Lo 3
Lo 4.......................
NOTE: Series 100 (heating only) and 150-200 have
3-speed motor.
Limit Control Safety Check — This control
shuts off the gas and energizes the blower
motor if the furnaee becomes overheated.
The recommended method of checking the
limit control is to gradually block off the return
air after the furnace has been operating for a
period of at least 5 minutes. As soon as the
limit has proven safe, the return air opening
should be unblocked to permit normal air circu­
lation. By using this method to check the limit
control, it can be established that the limit is
functioning properly and will “fail-safe” if there
is a motor failure.
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