Direct Vent Pressure Switch Connections; Direct Vent Manifold Pressure Check - American Standard 50A65-475 Manual

Direct Vent Pressure Switch Connections

Direct Vent Manifold Pressure Check

The 40" Direct Vent furnaces (single and two stage) ref-
erence the burner box inlet static to provide proper
gas valve regulation. The burner box static pressure
varies with the different inlet vent pipe lengths and am-
bient air conditions. Therefore, the gas valve regulator
must be able to reference the box pressure to maintain
a constant manifold setting. The gas valve vent port has
Note: The final manifold pressure will be higher than the reading indicates if the burner box
hose is not connected. The actual manifold pressure will be off by the same amount as
the burner box static pressure.
Example: 3.50" W.C. gas valve outlet pressure tap reading.
–.15" W.C. burner box inlet pressure hose not connected.
3.65" W.C. actual manifold pressure instead of desired 3.5" W.C.
The burner box pressure hose does not have to be connected to set the outlet
manifold pressure if the burner box front cover is removed.
a barbed hose fitting which connects with a "tee" fitting
to the burner box and combustion air switches.
When setting or checking the gas valve outlet manifold
pressure, the manometer must be connected to
both the gas valve outlet pressure tap and the burner
box pressure hose (see figures below).
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