Orifice Installation - Heat Wise SU-2A Manual

All burners are equipped with an orifice set at the appropriate firing rate. It sometimes may
be necessary to drill the orifice. Drilling the orifice increases the firing rate. To drill the orifice,
first open the stainless steel union and then unscrew the orifice from inside the union. Determine
the proper orifice size for the desired firing rate and drill the orifice (see Chart 3 and Chart 4).
Replace the orifice in the union and tighten the union so that it is gas tight. Once installed, a
higher or lower firing rate can be achieved by raising or lowering the manifold pressure by +/-
0.3". Pressure changes can only be made when the burner is running. A manometer must be used
to check and adjust the pressure. The typical working manifold pressure for natural gas is 3.5"
W.C . (2.3" W.C. for LPG). The maximum inlet pressure at the gas valve is 11" W.C .; the
minimum is 5" W.C. (for the purpose of input adjustment). Note: the minimum running input
pressure is 5" W.C. NOTE: The static pressure of the system may be within norm, but the
pressure drop when the system is running can reduce this greatly. Check the running pressure to
make sure there are no fluctuations in the pressure.
INSTALLING THE CHIMNEY LINER, DRAFT REGULATOR AND
Some utilities require new chimney liners for all gas installations. Use a corrosion resistant
chimney liner (approved for gas service) of the same size as the vent pipe. Use a double swing
draft regulator, listed by CSA or U.L. The vent pipe should extend only to (but not beyond) the
inside wall of the chimney. The draft over fire should always be positive.
Fig. 3 Gas Burner Piping*
*The dotted lines represent field installation.

ORIFICE INSTALLATION

VENT PIPE
6