Bryant 350MAV - Set Temperature Rise

CAUTION: DO NOT redrill orifices. Improper drilling
(burrs, out-of-round holes, etc.) can cause excessive
burner noise and misdirection of burner flames. This can
result in flame impingement of burners and heat exchang-
ers causing failures.
d. Replace gas valve regulator adjustment screw cap.
e. Replace burner enclosure front and verify adjusted gas
input rate using method outlined in item 3.
f. Look through sight glass in burner enclosure and check
burner flame. Burner flame should be clear blue, almost
transparent. (See Fig. 45.)
3. Verify natural gas input rate by clocking gas meter.
NOTE: Be sure all pressure tubing, combustion-air and vent
pipes, and burner enclosure front are in place when checking input
by clocking gas meter.
a. Calculate high-altitude adjustment (if required).
UNITED STATES
At altitudes above 2000 ft, this furnace has been ap-
proved for a 2 percent derate for each 1000 ft above sea
level. See Table 10 for derate multiplier factor.
CANADA
At installation altitudes from 2000 to 4500 ft, this furnace must be
derated 5 percent by an authorized Gas Conversion Station or
Dealer. To determine correct input rate for altitude, see example
above and use 0.95 as derate multiplier factor.
b. Turn off all other gas appliances and pilots.
c. Start furnace and let operate for 3 minutes.
d. Measure time (in sec) for gas meter test dial 1 revolution.
e. Refer to Table 11 for cu ft of gas per hr.
f. Multiply gas rate (cu ft/hr) X heating value (Btu/cu ft)
using natural gas heating value from local gas
utility/supplier.
EXAMPLE: (0-2000 ft altitude)
Furnace input from rating plate is 100,000 Btuh.
Btu heating input = Btu/cu ft X cu ft/hr
Heating value of gas = 975 Btu/cu ft
Time for 1 revolution of 2-cu ft dial = 70 sec
Gas rate = 103 cu ft/hr (from Table 11)
Btu heating input = 103 X 975 = 100,425 Btuh. In this
example, the orifice size and manifold pressure adjustment
is within ±2 percent of the furnace input rate.
B. Set Temperature Rise
CAUTION: Temperature rise must be within limits
specified on unit rating plate. Recommended operation is
at midpoint of rise or above. Failure to follow this caution
may result in condensing or overheating the heat ex-
changers.
Determine and adjust air temperature rise as follows:
1. Place thermometers in return and supply ducts as close to
furnace as possible. Be sure thermometers do not see heat
exchanger so that radiant heat does not affect readings. This
practice is particularly important with straight-run ducts.
A93059
BURNER
ORIFICE
Fig. 45—Burner Flame
A89020
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BURNER FLAME
BURNER
MANIFOLD
EXAMPLE:
100,000 Btuh input furnace installed at 4300 ft.
Derate Furnace Input Rate
Furnace Input Rate X Multiplier = at Installation
at Sea Level Factor Altitude
100,000 X 0.91 = 91,000
TABLE 10–ALTITUDE DERATE MULTIPLIER FOR U.S.A.
ALTITUDE
(FT)
PERCENT
OF DERATE
DERATE MULTIPLIER
FACTOR FOR U.S.A.*
0–2000 0 1.00
2001–3000 4–6 0.95
3001–4000 6–8 0.93
4001–5000 8–10 0.91
5001–6000 10–12 0.89
6001–7000 12–14 0.87
7001–8000 14–16 0.85
8001–9000 16–18 0.83
9001–10,000 18–20 0.81
* Derate multiplier factor is based on midpoint altitude for altitude range.
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