Rheem RGDG, Installation Instructions Manual, Page: 28 / 48

28
Furnaces for use on LP gas, the LP
gas supply pressure must be set
between 11.0
(
and 14.0
(
W.C. by
means of the tank or branch supply
regulators. The furnace manifold
pressure should be set at 10
(
W.C. at
the gas control valve. For elevations
up to 8,000 feet, rating plate input
ratings apply. For high altitudes
(elevations 8,000 and over) and for
any necessary major changes in the
gas flow rate the orifice spud must be
changed.
To change orifice spuds:
1. Shut off the manual main gas valve
and remove the gas manifold.
2. Replace the orifice spuds.
3. Reassemble in reverse order.
4. Turn the gas supply back on and
check for proper operation and
manifold pressure.
Check of input is important to prevent
over firing of the furnace beyond its
design-rated input. NEVER SET
INPUT ABOVE THAT SHOWN ON
THE RATING PLATE.
To check furnace input:
1. Make certain that all other gas
appliances are shut off, with the
exception of pilot burners.
2. Start the furnace
3. Time the meter to measure the time
required to burn one cubic foot of
gas.
4. Use Table 4 to determine input rate.
RATING PLATE ELEVATION
INPUT
BTU/HR 0 TO 7,999 FT. 8,000 FT. AND ABOVE
NATURAL GAS
HEATING VALUE @ 1,000 BTU/FT 3 , SPECIFIC GRAVITY 0.62
MANIFOLD PRESSURE @ 3.5
(
W.C.
45,000 43 45
50,000 42 43
67,500 43 45
75,000 42 43
100,000 42 43
125,000 42 43
150,000 42 43
L.P. GAS
HEATING VALUE @ 2,475 BTU/FT 3 , SPECIFIC GRAVITY 1.52/
MANIFOLD PRESSURE @ 10
(
W.C.
45,000 54 55
50,000 54 55
67,500 54 55
75,000 54 55
100,000 54 55
125,000 54 55
150,000 54 55
ORIFICE SIZING CHART
RATING PLATE ELEVATION
INPUT
BTU/HR 0 TO 1,999 FT. 2,000 FT. TO 4,500 FT.
NATURAL GAS
HEATING VALUE @ 1,000 BTU/FT 3 , SPECIFIC GRAVITY 0.62
MANIFOLD PRESSURE @ 3.5
(
W.C.
45,000 43 45
50,000 42 43
67,500 43 45
75,000 42 43
100,000 42 43
125,000 42 43
150,000 42 43
L.P. GAS
HEATING VALUE @ 2,475 BTU/FT 3 , SPECIFIC GRAVITY 1.52/
MANIFOLD PRESSURE @ 10
(
W.C.
45,000 54 55
50,000 54 55
67,500 54 55
75,000 54 55
100,000 54 55
125,000 54 55
150,000 54 55
ORIFICE SIZING CHART (CANADA)