Carrier 58MTA - Page 46

EXAMPLE: (0-2000 ft altitude using Table 10)
Heating value = 1050 Btu/cu ft
Specific gravity = 0.62
Therefore: Orifice No. 45
Manifold pressure 3.6-in. wc for high heat
1.5-in. wc for low heat
* Furnace is shipped with No. 45 orifices.
In thisexample all main burner orifices are the correct size
and do not need to be changed to obtain the proper
input rate.
g. Check and verify burner orifice size in furnace. NEVER
ASSUME ORIFICE SIZE; ALWAYS CHECK AND
VERIFY.
2. Adjust Manifold Pressure To Obtain Input Rate.
a. Remove burner enclosure front.
NOTE: Manifold pressure MUST always be measured with
burner enclosure front REMOVED.
b. Remove regulator seal caps that conceal adjustment screws
for low-and high-heat gas valve pressure regulators. (See
Fig. 53.)
c. Move setup switch SW-1 on control center to ON position.
This keeps furnace locked in low-heat operation.
d. Jumper R and W/W1 thermostat connections on control to
start furnace.
e. Turn low-heat adjusting screw (3/32 hex Allen wrench)
counterclockwise (out) to decrease input rate or clock-wise
(in) to increase input rate.
TABLE 10—MODEL 58MTA ORIFICE SIZE AND HIGH/LOW-HEAT MANIFOLD PRESSURES
FOR CORRECT INPUTS (Continued)
FOR USE WITH 060 THROUGH 120 SIZE FURNACES ONLY
(TABULATED DATA BASED ON 20,000/13,000 BTUH PER BURNER, DERATED 2 PERCENT FOR EACH 1000
FT ABOVE SEA LEVEL)*
ALTITUDE
RANGE
(FT)
AVG GAS
HEAT VALUE
(BTU/CU FT)
SPECIFIC GRAVITY OF NATURAL GAS
0.58 0.60 0.62 0.64 0.66
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
U.S.A. Only
7001
to
8000
15%
derate
625 43 3.8/1.6 42 3.3/1.4 42 3.4/1.4 42 3.5/1.5 42 3.6/1.5
650 43 3.5/1.5 43 3.7/1.6 43 3.8/1.6 42 3.2/1.4 42 3.3/1.4
675 44 3.8/1.6 43 3.4/1.4 43 3.5/1.5 43 3.6/1.5 43 3.7/1.6
700 44 3.5/1.5 44 3.6/1.5 44 3.8/1.6 43 3.4/1.4 43 3.5/1.5
725 44 3.3/1.4 44 3.4/1.4 44 3.5/1.5 44 3.6/1.5 44 3.7/1.6
750 45 3.7/1.6 45 3.8/1.6 44 3.3/1.4 44 3.4/1.4 44 3.5/1.5
775 45 3.5/1.5 45 3.6/1.5 45 3.7/1.6 45 3.8/1.6 44 3.3/1.4
800 45 3.3/1.4 45 3.4/1.4 45 3.5/1.5 45 3.6/1.5 45 3.7/1.6
825 47 3.6/1.5 45 3.2/1.3 45 3.3/1.4 45 3.4/1.4 45 3.5/1.5
850 47 3.4/1.4 47 3.5/1.5 47 3.7/1.5 45 3.2/1.3 45 3.3/1.4
ALTITUDE
RANGE
(FT)
AVG GAS
HEAT VALUE
(BTU/CU FT)
SPECIFIC GRAVITY OF NATURAL GAS
0.58 0.60 0.62 0.64 0.66
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
U.S.A. Only
Altitudes
8001
to
9000
17%
derate
600 43 3.8/1.6 42 3.3/1.4 42 3.4/1.4 42 3.5/1.5 42 3.6/1.5
625 43 3.5/1.5 43 3.6/1.5 43 3.8/1.6 42 3.2/1.4 42 3.3/1.4
650 44 3.7/1.6 43 3.4/1.4 43 3.5/1.5 43 3.6/1.5 43 3.7/1.6
675 44 3.5/1.5 44 3.6/1.5 44 3.7/1.6 44 3.8/1.6 43 3.4/1.5
700 44 3.2/1.4 44 3.3/1.4 44 3.4/1.5 44 3.6/1.5 44 3.7/1.6
725 45 3.6/1.5 45 3.8/1.6 44 3.2/1.4 44 3.3/1.4 44 3.4/1.4
750 45 3.4/1.4 45 3.5/1.5 45 3.6/1.5 45 3.8/1.6 44 3.2/1.4
775 45 3.2/1.3 45 3.3/1.4 45 3.4/1.4 45 3.5/1.5 45 3.6/1.5
800 47 3.6/1.5 47 3.7/1.6 45 3.2/1.3 45 3.3/1.4 45 3.4/1.4
ALTITUDE
RANGE
(FT)
AVG GAS
HEAT VALUE
(BTU/CU FT)
SPECIFIC GRAVITY OF NATURAL GAS
0.58 0.60 0.62 0.64 0.66
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
Orifice
no.
Manifold
Pressure
U.S.A. Only
9001
to
10,000
19%
derate
575 43 3.8/1.6 42 3.2/1.4 42 3.3/1.4 42 3.3/1.5 42 3.6/1.5
600 43 3.5/1.5 43 3.6/1.5 43 3.7/1.6 42 3.2/1.3 42 3.3/1.4
625 44 3.7/1.6 44 3.8/1.6 43 3.5/1.5 43 3.6/1.5 43 3.7/1.6
650 44 3.4/1.4 44 3.5/1.5 44 3.7/1.5 44 3.8/1.6 43 3.4/1.4
675 44 3.8/1.6 44 3.3/1.4 44 3.4/1.4 44 3.5/1.5 44 3.6/1.5
700 45 3.6/1.5 45 3.7/1.6 45 3.8/1.6 44 3.3/1.4 44 3.4/1.4
725 45 3.3/1.4 45 3.4/1.5 45 3.6/1.5 45 3.7/1.6 45 3.8/1.6
750 47 3.7/1.6 45 3.2/1.4 45 3.3/1.4 45 3.4/1.5 45 3.5/1.5
775 47 3.5/1.5 47 3.6/1.5 47 3.7/1.6 45 3.2/1.4 45 3.3/1.4
*Orifice numbers shown in shading are factory installed.
NOTE: Percents of derate are based on midpoints of U.S. altitude ranges.
46