Gas Pressure - Rheem 801S Series Installation Instructions Manual

GAS PRESSURE

IMPORTANT: ENSURE that the furnace gas valve is not to be
subjected to high gas line supply pressures.
DISCONNECT the furnace and its individual manual gas stop
from the gas supply piping during any pressure testing that ex-
ceeds 1/2 PSIG. (3.48 kPa).
Natural gas supply pressure must be 5" to 10.5" w.c. LP gas
supply pressure must be 11" to 13" w.c. This pressure must
be maintained with all other gas-fired appliances in opera-
tion.
The minimum gas supply pressure to the gas valve for proper fur-
nace input adjustments is 5" w.c. for natural gas, however 6" to 7"
is recommended. The minimum gas supply pressure is 11" w.c.
for LP gas.
ELEVATIONS ABOVE 2000 FT. REQUIRE THAT THE
FURNACE INPUT RATING BE ADJUSTED AND THAT
THE SIZE OF THE BURNER ORIFICES BE RECAL-
CULATED BASED ON ELEVATION AND GAS HEAT-
ING VALUE. THE BURNER ORIFICES MAY (OR MAY
NOT) NEED TO BE CHANGED. SEE THE SECTION
TITLED "HIGH ALTITUDE INSTALLATIONS" OF THIS
BOOK FOR INSTRUCTIONS.
TABLE 6
NATURAL GAS PIPE CAPACITY TABLE (CU. FT./HR.)
Capacity of gas pipe of different diameters and lengths in cu. ft. per hr. with pressure drop of 0.3 in. and specific
gravity of 0.60 (natural gas).
Nominal
Iron Pipe
Size, Inches 10 20
1/2 132 92
3/4 278 190
1 520 350
1-1/4 1,050 730
1-1/2 1,600 1,100
After the length of pipe has been determined, select the pipe size which will provide the minimum cubic feet per hour
required for the gas input rating of the furnace. By formula:
Cu. Ft. Per Hr. Required
The gas input of the furnace is marked on the furnace rating plate. The heating value of the gas (BTU/FT
termined by consulting the local natural gas utility or the LP gas supplier.
GAS SUPPLY (cont.)
FIGURE 20
TYPICAL GAS VALVE (HONEYWELL)
REGULATOR CAP
GAS VALVE
This furnace has a 24-volt gas valve. It has ports for measuring
supply and manifold gas pressure. The valve body contains a
pressure regulator to maintain proper manifold gas pressure.
A control switch is on the valve body. It can be set to only the
"ON" or "OFF" positions. The gas valve is a slow-opening valve.
See Figure 20.
When energized, it takes 2 to 3 seconds to fully open.
Length of Pipe, Feet
30 40 50 60
73 63 56 50
152 130 115 105
285 245 215 195
590 500 440 400
890 760 670 610
Gas Input of Furnace (BTU/HR)
=
Heating Value of Gas (BTU/FT
70 80
46 43
96 90
180 170
370 350
560 530
3 )
3 ) may be de-
25