Daikin DCG Series Service Instructions Manual page 33

SYSTEM OPERATION
R T L I
OOF OP OCATION AND
The gas supply piping location and installation for roof top
units must be in accordance with local codes or, in the
absence of locals codes, with ordinances of the latest edition
of the National Fuel Gas Code (ANSI Z223.1).
A manual gas shut off valve must be field installed external to
the roof top unit. In addition, a drip leg must be installed near
the inlet connection. A ground joint union connection is
required between the external shut off valve and the unit
connection to the gas valve to permit removal of the burner
assembly for servicing.
1. Route gas piping to unit so that it does not interfere with
the removal of access panels. Support and align piping to
prevent strains or misalignment of the manifold assem-
bly.
2. All units are furnished with standard female NPT pipe
connections. Connection pipe sizes for DCG090 through
300 units is 3/4" NPT The size of the gas supply piping
to the unit must be based on length of run, number of units
on the system, gas characteristics, BTU requirement
and available supply pressure. All piping must be done in
accordance with local codes or, in the absence of local
codes, with the latest edition of the National Fuel Gas
Code (ANSI Z223.1).
NOTE: The gas connection size at the unit does NOT
establish the size of the supply line.
3. These units are designed for either natural or propane
(LP) gas and are specifically constructed at the factory
for only one of these fuels. The fuels are NOT inter-
changeable. However, the furnace can be converted in
the field from natural gas to LP gas with the appropriate
factory kit (see unit Spec Sheet Manual for the appropri-
ate kit). Only a qualified contractor, experienced with
natural and propane gas systems, should attempt con-
version. Kit instructions must be followed closely to
assure safe and reliable unit operation.
4. With all units on a common line operating under full fire,
natural gas main supply pressure should be adjusted to
approximately 7.0" w.c., measured at the unit gas valve.
If the gas pressure at the unit is greater than 10.5" w.c.,
the contractor must furnish and install an external type
positive shut off service pressure regulator. The unit will
not function satisfactorily if supply gas pressure is less
than 5.5" w.c. or greater than 10.5" w.c..
NOTE: A minimum horizontal distance of 48" between
the regulator and the furnace flue discharge is required.
5. With all units on a common line operating under full LP
gas main supply pressure should be at least 11.0" w.c.
and must be no greater than 14.0" w.c., measured at the
unit gas valve. Unit will not function satisfactorily if supply
gas pressure is less than 11.0" w.c. or greater than 14.0"
w.c..
NSTALLATION
6. All pipe connections should be sealed with a pipe thread
compound, which is resistant to the fuel used with the
furnace. A soapy water solution should be used to check
all joints for leaks. A 1/8" NPT plugged tap is located on
the entering side of the gas valve for test gauge connec-
tion to measure supply (main) gas pressure. Another 1/
8" tap is provided on the side of the manifold for checking
manifold pressure.
T
HIS UNIT AND ITS INDIVIDUAL SHUTOFF VALVE MUST BE
DISCONNECTED
FROM THE GAS SUPPLY SYSTEM DURING ANY
PRESSURE TESTING OF THAT SYSTEM AT TEST PRESSURES IN EXCESS OF
1/2 PSIG (13.8" . .).
W C
T ISOLATED
HIS UNIT MUST BE
BY CLOSING ITS INDIVIDUAL MANUAL SHUTOFF VALVE DURING ANY
PRESSURE TESTING EQUAL TO OR LESS THAN
7. There must be no obstruction to prevent the flow of
combustion and ventilating air. A vent stack is not
required and must never be used. The power venter will
supply an adequate amount of combustion air as long as
the air passageways are kept free of any obstructions
and the recommended external unit clearances are
maintained.
CIRCULATING AIR AND FILTERS
D
UCTWORK
The supply duct should be provided with an access panel
large enough to inspect the air chamber downstream of the
heat exchanger. A cover should be tightly attached to prevent
air leaks.
Ductwork dimensions are shown in the roof curb installation
manual.
If desired, supply and return duct connections to the unit may
be made with flexible connections to reduce possible unit
operating sound transmission.
VENTING
NOTE: Venting is self-contained.
CONDENSATE DRAIN CONNECTION
C D C
ONDENSATE RAIN ONNECTION
A 3/4" female NPT drain connection is supplied on the end of
the condensate pan, with an alternative connection on the
bottom of the pan. An external trap must be installed for
proper condensate drainage.
WARNING
CAUTION
FROM THE GAS SUPPLY PIPING SYSTEM
1/2 PSIG.
33