Operating instructions
terminal. See Table 13 for lead color identification. Recon-
nect original lead on SPARE terminal.
Follow this same procedure for proper selection of COOL
speed selection.
C. Adjust Blower Off Delay (Heat Mode)
The blower off delay has 4 adjustable settings from 90 sec to 180
sec. (See Table 14.) The blower off delay jumpers are located on
the furnace control board (See Fig. 31). To change the blower off
delay setting, move the jumper from one set of pins on the control
board to the pins used for the desired blower off delay. Factory
blower off delay setting is 120 sec.
D. Set Thermostat Heat Anticipator
When using a nonelectronic thermostat, the thermostat heat
anticipator must be set to match the amp draw of the electrical
components in R-W circuit. Accurate amp draw readings can be
obtained at thermostat subbase terminals R and W. Fig. 60
illustrates an easy method of obtaining actual amp draw. The amp
reading should be taken after blower motor has started and furnace
is heating. Connect ammeter wires as shown in Fig. 60. The
thermostat anticipator should NOT be in the circuit while measur-
ing current. If themostat has no subbase, the thermostat must be
disconnected from R and W wires during current measurement.
See thermostat manufacturer’s instructions for adjusting heat
anticipator and for varying heating cycle length. For an electronic
thermostat, set cycle rate for 3 cycles per hour.
V. CHECK SAFETY CONTROLS
This section covers the safety controls that must be checked before
the installation is complete. The flame sensor, gas valve, and
pressure switch were all checked in the Start-up procedure section
as part of normal operation.
TABLE 10—MODEL 350MAV ORIFICE SIZE AND MANIFOLD PRESSURE FOR CORRECT INPUT (CONTINUED)
FOR USE WITH 140 SIZE FURNACES ONLY
(TABULATED DATA BASED ON 23,000 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. and Canada
4001
to
5000
9%
derate
725 41 3.6 41 3.7 41 3.8 40 3.6 40 3.8
750 42 3.7 42 3.8 41 3.6 41 3.7 41 3.8
775 42 3.5 42 3.6 42 3.7 42 3.8 41 3.6
800 42 3.3 42 3.4 42 3.5 42 3.6 42 3.7
825 42 3.7 42 3.2 42 3.3 42 3.4 42 3.5
850 43 3.5 43 3.6 43 3.8 42 3.2 42 3.3
875 43 3.3 43 3.4 43 3.6 43 3.7 43 3.8
900 43 3.1 43 3.3 43 3.4 43 3.5 43 3.6
925 43 3.0 43 3.1 43 3.2 43 3.3 43 3.4
950 43 2.8 43 3.9 43 3.0 43 3.1 43 3.2
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. and Canada
5001
to
6000
11%
derate
700 41 3.5 41 3.7 41 3.8 40 3.6 40 3.7
725 42 3.7 42 3.8 41 3.5 41 3.6 41 3.8
750 42 3.4 42 3.5 42 3.7 42 3.8 41 3.5
775 42 3.2 42 3.3 42 3.4 42 3.5 42 3.7
800 43 3.7 43 3.8 42 3.2 42 3.3 42 3.4
825 43 3.5 43 3.6 43 3.7 43 3.8 42 3.2
850 43 3.3 43 3.4 43 3.5 43 3.6 43 3.7
875 43 3.1 43 3.2 43 3.3 43 3.4 43 3.5
900 43 2.9 43 3.0 43 3.1 43 3.2 43 3.3
925 43 2.7 43 2.8 43 2.9 43 3.0 43 3.1
950 43 2.6 43 2.7 43 2.8 43 2.9 43 3.0
975 43 2.5 43 2.6 43 2.6 43 2.7 43 2.8
1000 43 2.3 43 2.4 43 2.5 43 2.6 43 2.7
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
6001
to
7000
13%
derate
650 41 3.8 40 3.6 40 3.7 40 3.8 39 3.7
675 41 3.5 41 3.6 41 3.7 40 3.6 40 3.7
700 42 3.6 42 3.7 41 3.5 41 3.6 41 3.7
725 42 3.4 42 3.5 42 3.6 42 3.7 42 3.8
750 43 3.8 42 3.3 42 3.4 42 3.5 42 3.6
775 43 3.6 43 3.7 43 3.8 42 3.3 42 3.4
800 43 3.4 43 3.5 43 3.6 43 3.7 43 3.8
825 43 3.2 43 3.3 43 3.4 43 3.5 43 3.6
850 43 3.0 43 3.1 43 3.2 43 3.3 43 3.4
875 43 2.8 43 2.9 43 3.0 43 3.1 43 3.2
*Orifice numbers 43 are factory installed.
Percents of derate are based on midpoints of U.S. altitude ranges.
—45—