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VII. Condensate Piping
Figure 12
Standpipe Assembly
The Air Command 90 and 95 achieves its high efficiency by
condensing some of the flue products into a slightly acidic
water which must be piped to a drain. A standpipe, which
is shipped with the furnace, must be installed on the right
side of the furnace cabinet (Figure 12). The condensate
from the recuperative coil and the induced draft blower
flows into this standpipe which acts as a trap. No other trap
may be used. A 3/4 inch PVC or CPVC pipe must be run
from the side of the standpipe to a drain, maintaining a
horizontal downward slope in accordance with good plumb-
ing practices. Do not trap this line.
PVC or CPVC pipe is recommended since it is corrosion
resistant, rigid, and not easily damaged. The drain line
must not be routed outside where it could freeze and
become blocked. The top of the standpipe must be left
open so any blockage in the drainline will be relieved out
the tip of the standpipe and not back up into the unit.
If an air conditioning coil is installed with the furnace, a
common drain can be used (install as shown in Figure 13).
Leaving an open tee near the cooling coil will allow positive
air pressure in the supply air plenum be relieved out the tee
without interfering with draining of the furnace condensate.
Figure 13
Common Drain Installation
VIII. Gas Piping
The rating plate is stamped with the model number, type of
gas and gas input rating. Make sure the furnace is equipped
to operate on the type of gas available.
Inlet Gas Pressure
Natural
Min. 5.0" W.C., Max. 10.0" W.C.
Propane
Min. 11.0" W.C., Max. 13.0" W.C.
Inlet gas pressure must not exceed the maximum value
shown in table above.
The minimum supply pressure must be maintained to
prevent unreliable ignition. In addition, gas input to the
burners must not exceed the rated input shown on the
rating plate. Overfiring the furnace could result in prema-
ture heat exchanger failure.
High Altitude Derate (U.S. Installations Only)
When this furnace is installed at altitudes above 2,000 feet
above sea level the furnace input must be derated 4
percent for each 1,000 feet above sea level because the
density of the air is reduced.
In some areas the gas supplier will derate the gas at a rate
of 4% for each 1,000 feet above sea level. It this is not
done, smaller orifices will be required at altitudes above
3,500 feet (non-derated natural gas) or 4,500 feet (non-
derated propane gas).
A different pressure switch is required at altitudes more
than 4,000 feet above sea level. This is required regard-
less of the heat content of the fuel used.
High altitude kits are purchased according to the altitude
and usage of either propane gas or natural gas. Refer to
the Amana distributor for required high altitude kit(s).
Do not derate the furnace by adjusting the manifold pres-
sure to a lower pressure than specified on the furnace
nameplate. With a lower air density and a lower manifold
pressure at the burner orifice, the orifice will not supply the
proper amount of air into the burner, causing incomplete
combustion of the gas, flashback, and possible yellow
tipping.
GAS PIPING
Important Note: To avoid possible unsatisfactory operation
or equipment damage due to underfiring of equipment, do
not undersize the natural/propane gas piping from the
meter/tank to the furnace. Include all appliances which may
be operated simultaneously when sizing a trunk line.
The gas pipe supplying the furnace must be properly sized
based on gas flow required, specific gravity of the gas and
length of the run. The gas line installation must comply with
local codes, or in the absence of local codes, with the latest
edition of the National Fuel Gas Code, NFPA 54/ANSI
Z223.1.
Page 14
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