Installation Instructions

Total load and regulator size:
Calculate the total appliance load and
determine if one regulator has sufficient
capacity to supply this load. One regulator is
normally adequate when appliances are close
t
ogether. When groups of high-load appliances
are widely separated, it is often more economi-
cal to use one pressure reducing regulator to
supply each appliance group. The total
appliance load required is 169 CFH (169,000
BTUH). The supply pressure from the meter is 2
psig and the designated pressure drop from the
meter to the regulator is 1 psig; thus the
minimum inlet pressure to the regulator is 1 psig. Since the outlet pressure of the regulator is set at 8" WC, the expected pressure
drop across the regulator is 20 inches WC (1 psig - 8" WC = 20" WC). A single 325-3 regulator has a flow rate capacity of 252
CFH. This capacity exceeds the system requirement of 169 CFH. In cases where the 325-3 regulator capacity is insufficient, a
larger #325-5A regulator or parallel arrangement of two regulators should be used.
SIZING SECTION A (METER TO REGULATOR):
Section A must be sized to handle all appliances loads and supply the pressure reducing (pounds to inches) regulator. The total
load is 169 CFH and the length is 10 ft. The supply pressure is 2 psig and the pressure drop is 1 psig. Referring to Table 5 (meter
to regulator with 2 psig inlet and 1 psig drop) under the 10 ft. column, we find that 3/8 inch has capacity over 169 CFH (332 CFH).
Use 3/8" tubing to run Section A. To size the other sections, the pressure source is the outlet of the pressure regulator rather than
the meter. Use the low-pressure Table 3 (8.0" WC inlet with 3.0" WC drop) and size each section individually using the appliance
load and run distance.
SIZING SECTION B
Section B supplies the oven/range. The load is 45 CFH and the distance between the regulator outlet and appliance is 20 ft. The
total pressure drop is from the outlet of the reducing regulator to the oven/range. The outlet pressure from the regulator is 8" WC
and the pressure drop is 3" WC. Referring to Table 3, under the 20 ft. length column, we find that an 8 inch has a flow capacity
above 45 CFH (81 CFH). Use 3/8" tubing to run Section B.
SIZING SECTION C:
Section C supplies the furnace. The load is 75 CFH and the distance is 5 ft. Referring to Table 3, under the 5 ft. length column, we
find that 3/8 inch has a flo
w capacity abo
ve 75 CFH (162 CFH). Use 3/8" tubing to run Section C.
SIZING SECTION D:
Section D supplies the dr
y
er
.
The load is 25 CFH and the distance is 35 ft. Referring to Table 3, and since a 35 ft. length column
does not exist, use the 40 ft. length column. We find that 318 inch has a flow capacity above 25 CFH (58 CFH). Use 3/8" tubing to
run Section D.
SIZING SECTION E:
Section E supplies the water heater. The load is 24 CFH and the distance is 50 ft. Referring to Table 3, under the 50 ft. length
column, we find that 3/8 inch has a flo
w capacity above 24 CFH (51 CFH). Use 3/8" tubing to run Section E.
13
E
XAMPLE #3 - ELEVATED DUAL PRESSURE SYSTEM
This is a 2 psig supply pressure parallel arrangement. The natural gas
system incorporates a pressure reducing regulator with a distribution
tee manifold located closely to several large capacity appliances. The
inlet pressure downstream of the meter is 2 psig, and the designated
maximum pressure drop from the meter to the reducing regulator is
1.0 psig. The outlet pressure from the regulator is set at 8 inches
water column. A 3" WC pressure drop is used in sizing the tubing from
the regulator outlet to each appliance. Specified gravity of the gas
delivered is .60 and energy content is 1 CFH 1,000 BTUH.
APPLIANCE LOADS LENGTHS TUBE SIZE
METER TO REGULATOR A= 10 FEET 3/8"
OVEN/RANGE = 45 CFH B = 20 FEET 3/8"
FURNACE = 75 CFH C = 5 FEET 3/8"
DRYER = 25 CFH D = 35 FEET 3/8"
WATER HEATER=24 CFH E = 50 FEET 3/8"
TOTAL...........................................169 CFH
E
levated (2 psig) Dual Pressure Natural Gas (Parallel System)