![Fig. 58—Burner Flame](/images/new-backgrounds/47908/47908111x1.webp)
BURNER FLAME
BURNER
MANIFOLD
A89020
Fig. 58—Burner Flame
EXAMPLE:
100,000 Btuh input furnace installed at 4300 ft.
Furnace Input Rate |
| Derate |
| Furnace Input Rate | |
X | Multiplier | = | at Installation | ||
at Sea Level | |||||
| Factor |
| Altitude | ||
|
|
| |||
100,000 | X | 0.91 | = | 91,000 | |
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Table 14—Altitude Derate Multiplier for U.S.A.
ALTITUDE | PERCENT | DERATE MULTIPLIER |
(FT) | OF DERATE | FACTOR FOR U.S.A.* |
0 | 1.00 | |
0.95 | ||
0.93 | ||
0.91 | ||
0.89 | ||
0.87 | ||
0.85 | ||
0.83 | ||
0.81 |
* Derate multiplier factor is based on midpoint altitude for altitude range.
Furnace must operate within the temperature rise ranges specified on the furnace rating plate. Determine the air temperature as follows:
1.Place thermometers in return and supply ducts as close to furnace as possible. Be sure thermometers do not ’see’ heat exchangers so that radiant heat does not affect thermometer readings. This practice is particularly important with straight run ducts.
2.When thermometer readings stabilize, subtract
NOTE: Temperature rise can be determined for
3.This furnace is capable of automatically providing proper airflow to maintain the temperature rise within the range specified on unit rating plate. If temperature rise is outside this range, proceed as follows:
a.Check gas input for low- and
b.Check derate for altitude if applicable.
c.Check all return and supply ducts for excessive restrictions causing static pressure greater than
d.Ensure bypass humidifier switch (BPH) setup switch
e.Check Troubleshooting Guide for
C. Set Thermostat Heat Anticipator
The thermostat heat anticipator must be set to match the amp draw of components in the
Fig. 59 illustrates an easy method of obtaining thermostat amp draw measurements. The amp reading should be taken after blower motor has started and furnace is operating in low heat.
1.To operate furnace in low heat, turn setup switch