11
200 PSIG
Maximum
5 to 15 PSIG
(20 PSIG Max.)
Continuous
11" W.C.
Second Stage
Regulator
First Stage
Regulator
Typical Propane Gas Piping
R
OOF
T
OP
L
OCATION
AND
I
NSTALLATION
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 be-
tween 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 assembly.
2. All units are furnished with standard female NPT pipe
connections. Connection pipe sizes for DCG036 through
072 units is 1/2" NPT on 045 to 140 mBH units. 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 interchangeable.
However, the furnace can be converted in the field from
natural gas to LP gas with the appropriate factory kit (see
unit Technical Manual for the appropriate kit). Only a
qualified contractor, experienced with natural and propane
gas systems, should attempt conversion. 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 13.0" 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 13.0" w.c..
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 tap is located on the entering side of
the gas valve for test gauge connection to measure supply
(main) gas pressure. Another tap is provided on the
manifold side of the gas valve 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
.).
WARNING
T
HIS
UNIT
MUST
BE
ISOLATED
FROM
THE
GAS
SUPPLY
PIPING
SYSTEM
BY
CLOSING
ITS
INDIVIDUAL
MANUAL
SHUTOFF
VALVE
DURING
ANY
PRESSURE
TESTING
EQUAL
TO
OR
LESS
THAN
1/2
PSIG.
CAUTION
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 from the unit through a wall may be installed with-
out clearance. However, minimum unit clearances must be main-
tained (see “Clearances” section). The supply duct should be pro-
vided with an access panel large enough to inspect the air cham-
ber 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.
