Installation Guide
14
Sizing and Congurations
Step 2 Size Section B: Determine the length of the run from the meter to the range oven and
the load delivered.
• The length from the meter to the range oven is 20 feet (A + B), and the load is 40
CFH (40,000 BTUH divided by 1000 CF per BTU).
• Consulting Table 7.1, we see that for a 20-foot run, ½" tubing will supply up to 51
CFH. The correct size tubing for section B is ½".
Step 3 Size Section C: Determine the length of the run from the meter to the water heater and
the load delivered.
• The length is 27 feet (A + C) and the load is 25 CFH (25,000 BTU).
• Consulting Table 7.1, we see that for a 30-foot run, ½" tubing will supply up to 42
CFH. The correct size for section C is ½".
Example 2: Medium Pressure in a Parallel Arrangement
This system is typical of a single family residential installation with several appliances. As it is
a medium-pressure system, the allowable pressure drop of 6 inches w.c. is greater than what
would have been
permissible in a
low pressure sys-
tem.
Step 1 Size Section A: Determine the longest run from the meter to any appliance:
• Meter (A) to water heater (D) is the longest run at 32 feet.
• The maximum load transported by section A is the total load of all appliances:
dryer + furnace + water heater + range oven = 155,000 BTU = 155 CFH.
• Consulting Table 7.4, the columns nearest 32' are 30' and a 40'. Because we must
use the length value that is greater than or equal to the measured run, the 40'
column is correct. Our total load is 155 CFH, and ½" tubing has a total maximum
capacity of 116 CFH at 40 feet, which is not enough for this system. ¾" Tubing has
a maximum capacity of 398 CFH. ¾" Tubing is the correct size.
Step 2 Size Section B: Determine the length from the meter to the dryer:
• A + B = 30 feet and the total load is the load of the dryer is 30,000 BTUH = 30 CFH.
• Table 7.4 shows that ½" tubing has a total load capacity of 133 CFH at 30 feet,
exceeding the load of the dryer, so ½" tubing is the correct size.
Step 3 Size Section C: Determine the length from the meter to the Furnace.
• A + C = 28 feet, and the total load is 60,000 BTUH = 60 CFH.
• Table 7.4 shows that ½" tubing has a total load of 133 CFH at 30 feet, so ½" tubing
is the correct size.
Gas
Meter
25,000 BTUH
Range Oven
40,000 BTUH
Elevated
Pressure
60,000 BTUH30,000 BTUH
Furnace
Water
Heater
Dryer
Figure 3.6 Medium Pressure System—Parallel Arrangement
A
B
C
D
E
Length of Runs:
A = 20' B = 10' C= 8'
D = 12' E = 10'
Supply: 12-14" w.c.
Pressure Drop: 6" w.c.