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Service Reference Manual ACCESSORIES
7-15
SRM-HW/HWC 8/99
AHALT390-1 High Altitude Kit
The AHALT390-1 kit contains the following parts to convert the 26, 38, 51
and 64HW/HWC series units to high altitude for natural or propane gas. If
the field conversion is for high altitude propane gas, be sure to install the
appropriate gas valve conversion kit (see page 7-14).
Regulator - Natural Gas
The minimum permissible gas supply pressure is 5.0" W.C. for purpose of
input adjustment. Gas input must never exceed the input capacity shown
on the rating plate. The furnace is equipped for rated inputs with manifold
pressure of 3.5" W.C. for natural gas. Only small variations in gas input
may be made by adjusting the regulator. In no case should the final
manifold pressure vary more than 0.3" W.C. from the specified pressure.
To check this pressure:
1. Turn off the gas valve.
2. Remove the plug on the valve marked “OUTLET PRESSURE”.
3. Install a water manometer.
Turn gas valve “ON”. If manifold pressure must be adjusted, remove cap
from pressure regulator and turn adjustment screw clockwise to increase
pressure, counterclockwise to reduce pressure. After checking pressure,
turn gas off, remove the manometer fitting and replace the pipe plug and
regulator cap. Put furnace in operation and leak check plug for leaks
using a soapy solution.
Check the furnace rate by observing the gas meter, when available,
making sure all other gas appliances are turned off. The test hand on the
meter should be timed for at least one revolution. Note the number of
seconds for one revolution.
TABLE 7-7 AHALT390-1 Parts List
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