Tempstar (F/G)9MAC0601714A Service And Technical Support Manual page 6

SERVICE AND TECHNICAL SUPPORT MANUAL
Table 1 Altitude Derate Multiplier for U.S.A.
ALTITUDE PERCENT
FT. (M) OF DERATE
0–2000
0
(0−610)
2001–3000
4−6
(610−914)
3001–4000
6−8
(914−1219)
4001–5000
8−10
(1219−1524)
5001–6000
10−12
(1524−1829)
6001–7000
12−14
(1829−2134)
7001–8000
14−16
(2134−2438)
8001–9000
16−18
(2438−2743)
9001–10,000
18−20
(2743−3048)
* Derate multiplier factors are based on midpoint altitude for altitude range.
NOTE: For Canadian altitudes of 2000 to 4500 ft. (610 to
1372 M), use USA altitudes of 2001 to 3000 ft. (610 to 914
M).
NOTE: If orifice hole appears damaged or it is suspected to
have been redrilled, check orifice hole with a numbered drill bit
of correct size. Never redrill an orifice. A burr−free and squarely
aligned orifice hole is essential for proper flame characteristics.
The inlet gas pressure must be checked with the furnace
operating in maximum heat. This is necessary to make sure the
inlet gas pressure does not fall below the minimum pressure of
4.5−in. w.c. for natural gas. The maximum inlet gas pressure is
13.6−in. w.c. If the inlet pressure is too low, you will not be able
to adjust the manifold pressure to obtain the proper input rate.
To check the inlet gas pressure:
1. Make sure the gas supply is turned off to the furnace and
at the electric switch on the gas valve.
2. Remove the 1/8 inch NPT plug from the inlet pressure
tap on the gas valve.
3. Connect a manometer to the inlet pressure tap on gas
valve.
4. Turn on furnace power supply.
5. Turn gas supply manual shutoff valve to ON position.
6. Turn furnace gas valve switch to ON position.
7. Jumper the R to W/W1 and W2 thermostat connections
at the furnace control board.
8. When main burners ignite, confirm inlet gas pressure is
Between 4.5−in. w.c. and 13.6−in. w.c.
9. Remove jumper across thermostat connections to
terminate call for heat. Wait until the blower off delay is
completed.
10. Turn furnace gas valve electric switch to OFF position.
11. Turn gas supply manual shutoff valve to OFF position.
12. Turn off furnace power supply.
13. Remove manometer from the inlet pressure tap of the
gas valve.
14. Apply pipe dope sparingly to end of inlet gas pipe plug
and re−install in the gas valve.
For proper operation and long term reliability, the manifold
pressure must be adjusted within +2 percent of input rate on
furnace rating plate.
The modulating furnace manifold pressure is set at two points.
The first point is Maximum Heat. The second point is Minimum
6
DERATE MULTIPLIER
FACTOR*
1.00
0.95
0.93
0.91
0.89
0.87
0.85
0.83
0.81
Specifications subject to change without notice.
Heat. Do not adjust Intermediate Heat manifold pressure.
Intermediate Heat manifold pressure is checked as part of the
temperature rise, but is not adjustable. Always adjust Maximum
Heat first, then Minimum Heat.
NOTE: DO NOT set Maximum Heat manifold pressure less
than 3.2−in. w.c. or more than 3.8−in. w.c. for natural gas.
To adjust manifold pressure to obtain input rate for Maximum
Heat:
1. Make sure the gas supply is turned off to the furnace and
at the electric switch on the gas valve.
2. Remove the 1/8 inch NPT plug from the outlet pressure
tap on the gas valve.
3. Connect a manometer to the outlet pressure tap on gas
valve.
4. Turn on furnace power supply.
5. Turn gas supply manual shutoff valve to ON position.
6. Turn furnace gas valve switch to ON position.
7. Jumper the R to W/W1 and W2 thermostat connections
at the furnace control board.
8. After the main burners ignite and the blower starts,
confirm Maximum Heat manifold pressure is correct,
based on the manifold pressure tables in the installation
instructions.
9. To adjust the Maximum Heat manifold pressure, slowly
turn adjusting screw counterclockwise (out) to decrease
manifold pressure or clockwise (in) to increase manifold
pressure. Turn adjustment no more than one click per
second until you obtain the required manifold pressure.
10. Main burner flame should be clear blue, almost
transparent.
11. After adjusting the Maximum Heat manifold pressure,
remove jumpers across thermostat connections to
terminate the call for heat.
12. Wait for blower off-delay to finish then reset 115-v power
to furnace.
To adjust manifold pressure to obtain input rate for Minimum
Heat:
1. Turn SW1−2 ON at the furnace control. Set up switch
SW4−2 must be OFF.
2. Jumper R and W/W1 thermostat connections on control
to start furnace.
3. After the main burners ignite and the blower starts,
confirm Minimum Heat manifold pressure is correct,
based on the manifold pressure tables in the installation
instructions.
4. To adjust the Minimum Heat manifold pressure, slowly
turn adjusting screw counterclockwise (out) to decrease
manifold pressure or clockwise (in) to increase manifold
pressure. Turn adjustment no more than one click per
second until you obtain the required manifold pressure.
5. After adjusting the manifold pressure, remove jumpers
across thermostat connections to terminate the call for
heat. Wait until the blower off delay is completed.
6. Move setup switch SW1-2 to the OFF position.
7. Turn gas supply manual shutoff valve to OFF position.
8. Turn off furnace power supply.
9. Remove manometer from the inlet pressure tap of the
gas valve.
10. Apply pipe dope sparingly to end of inlet gas pipe plug
and re-install in the gas valve.
11. Re-install cap over adjustment screw on the top of the
gas valve.
Gas Furnace: (F/G)9MAC
440 04 4201 01