Desert Aire Aura QS, Installation And Operation Manual

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A union or flanged connection shall be provided downstream from the manual
valve to permit removal of controls. Provide a 1/8” N.P.T. plugged tapping at
the inlet of the gas control for connection of a test gauge to check gas supply
pressure to the furnace. Unions must be a ground joint type or flanged-jointed
using a gasket resistant to LP gas. Pipe dope or sealant certified to be
resistant to the action of liquefied petroleum gases should be used on all
threaded joints.
• A drip leg must be used on both LP and natural gas installations prior to the
furnace to trap oil, condensate and other impurities which might otherwise
lodge in the gas valve or plug the burner orifice. When there is excessive
condensation between the gas meter and the furnace, a drip leg shall be
provided at the outlet of the gas meter. Failure to install a drip leg may void
the warranty on the dehumidifier.
• High fire manifold gas pressure is regulated by the combination valve to 3.5”
wc. Inlet pressure to the valve must be a minimum 5” wc or as noted on the
rating plate and maximum of 14” wc for natural gas. Note: Always check the
rating plate for minimum gas supply pressure. Minimum supply pressure
requirements vary based on size of burner and gas control option. Most units
require a minimum of 5” wc as stated above, but Sizes 350 and 400 with
electronic modulation require a minimum of 6” wc natural gas supply pressure.
•
LP Only:
Experience has proved that the pressure drop in the gas line
running from the outside propane gas tank to the gas appliances inside is the
most frequent cause of equipment malfunctions. A single pressure regulator,
located at the tank, will not reliably regulate the high tank pressures (up to
200 psi) down to 11” wc. Varying pressures will occur at the appliances as
outside temperatures and usage demands vary. Two-stage regulation is the
only effective method of controlling these variables.
First Stage
Regulation
L. P. Gas
Tank
Second Stage
Regulator
Typical 2-Stage L. P. Gas Piping
Size All Pipe In
Accordance With
NFPA-54 And NFPA-58
11"-14" Water Column
Pressure At All Times.
(Check Pressure At Burner)
Figure 11 - Recommended LP Gas Piping Method
Desert Aire - QS/QV Manual