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3 -   Select indoor blower speed tap, which provides a 
temperature rise within the  range  specied on  the 
rating plate. 
4 -  Verify manifold gas pressure 
NOTE: For purpose of this measurement, the minimum 
permissible gas supply pressure is 5” w.c. for natural gas. 
a.  Slide  the  gas valve  switch  to  the  “OFF”  position  (see 
Figure 24). 
b. Remove plug on valve marked “OUTLET PRESSURE.” 
c. Install a water manometer. 
Heat Exchanger
d.  Slide the gas valve switch to the “ON” position and initi-
ate a call for heat. During steady state operation, mani-
fold pressure should be: 
Manifold Pressure  
(non-adjustable)
2.7 - 3.1" w.c.
e.  After verifying pressure, turn gas o, remove manome-
ter tting, and replace pipe plug and regulator cap. 
f.  Put unit in operation and check plug for leaks using 
soapy solution.
FIGURE 28. Gas Valve, Manifold and Heat Exchanger Assembly