For 8” Wc – 10.5” Wc Initial Supply Pressure; Sample Gas Line; Maximum Undiluted Propane (Lp) Delivery Capacity - Noritz NR501-OD Service Manual

Table 2. For 8" WC – 10.5" WC initial supply pressure
Maximum Natural Gas Delivery Capacity (3.0" Pressure Drop)
Pipe
10' 20'
Size
(3m) (6m)
1/2" 454
3/4" 949
1" 1,787 1,228
1 1/4" 3,669 2,522
1 1/2" 5,497 3,778
2" 10,588 7,277
2 1/2" 16,875 11,598
3" 29,832 20,503
4" 43678 30,020
Values in Table are in Cubic Feet of Gas per Hour (0.60 Specific Gravity, 3.0" Pressure Drop, 8.0" WC or greater supply pressure, inlet
pressure less than 2psi). Contact your gas supplier for BTU/Cubic Foot ratings. For simplification of your calculations, 1 Cubic Foot of
Gas is approximately equivalent to 1000 BTU.

Sample Gas Line

Noritz Condensing Tankless Gas Water Heater
(120,000 Btuh)
Outlet E
10' (3m)
Section 4 Section 3 Section 2
5' (1.5m) 5' (1.5m)
Outlet D
10' (3m)
Gas Fireplace
(25,000 Btuh)
Natural Gas
Meter
Table 3. Maximum Undiluted Propane (LP) Delivery Capacity in Thousands of
BtuH (0.5" WC Pressure Drop)
Pipe
10' 20'
Size
(3m) (6m)
1/2" 275 189
3/4" 567 393
1" 1,071 732
1 1/4" 2,205 1,496
1 1/2" 3,307 2,299
2" 6,221 4,331
For reference only. Please consult gas pipe manufacturer for actual pipe capacities.
Final Check
When the installation is complete, verify that inlet gas pressure for the entire gas system does not
drop below 5" WC for NG or 8" WC for LP at all appliances. This can be tested by turning on all
gas burning appliances including the water heater, then check the inlet pressure at each appliance
to verify all appliances are receiving a minimum of 5" WC for NG or 8" WC for LP. If all appliances
are not receiving the minimum inlet pressure the gas piping system may need to be changed.
30' 40'
(9m) (12m)
312 250 214
652 524 448
986 844
2,025 1,733
3,034 2,597
5,844 5,001
9,314 7,971
16,465 14,092
24,107 20,632
Barbecue
(50,000 Btuh)
Outlet A
Clothes Dryer
(35,000 Btuh)
Outlet C
5' (1.5m)
Section 1
5' (1.5m)
10' (3m)
5' (1.5m)
Outlet B
Gas Range Stove
(65,000 Btuh)
30' 40' 50'
(9m) (12m) (15m) (18m) (21m) (24m) (27m) (30m) (38m) (45m) (60m)
152 129 114
315 267 237
590 504 448
1,212 1039 913
1,858 1,559 1,417
3,465 2,992 2,646
Length (including fittings)
50' 60' 70'
(15m) (18m) (21m)
190 172 158
397 360 331
748 678 624
1,536 1,392 1,280
2,302 2,085 1,919
4,433 4,016 3,695
7,065 6,401 5,889
12,489 11,316 10,411
18,286 16,569 15,243
Instructions
1. Size each outlet branch starting from the furthest
using the Btuh required and the length from the meter.
2. Size each section of the main line using the length to
the furthest outlet and the Btuh required by everything
after that section.
Sample Calculation (Using 3.0" WC Pressure Drop Table)
10' (3m)
Outlet A: 45' (13.5m) (Use 50' (15m)), 50,000 Btuh requires 1/2"
Outlet B: 40' (12m), 65,000 Btuh requires 1/2"
Section 1: 45' (13.5m) (Use 50' (15m)), 115,000 Btuh requires 1/2"
Outlet C: 30' (9m), 35,000 Btuh requires 1/2"
5' (1.5m)
Section 2: 45' (13.5m) (Use 50' (15m)), 150,000 Btuh requires 1/2"
Outlet D: 25' (7.5m) (Use 30' (9m)), 25,000 Btuh requires 1/2"
Section 3: 45' (13.5m) (Use 50' (15m)), 175,000 Btuh requires 1/2"
Outlet E: 25' (7.5m) (Use 30' (9m)), 120,000 Btuh requires 1/2"
Section 4: 45' (13.5m) (Use 50' (15m)), 295,000 Btuh requires 3/4"
Length (including fittings)
60' 70' 80'
103 96 89
217 196 185
409 378 346
834 771 724
1,275 1,181 1,086
2,394 2,205 2,047
CAUTION
66
80' 90' 100'
(24m) (27m) (30m)
147 138
308 289
580 544
1,191 1,118
1,785 1,675
3,437 3,225
5,479 1,540
9,865 9,087
14,181 13,305 12,568
90' 100' 125'
83 78 69
173 162 146
322 307 275
677 630 567
1,023 976 866
1,921 1,811 1,606
125'
(38m)
131 116
273 242
514 456
1,056 936
1,582 1,402
3,046 2,700
4,856 4,303
8,584 7,608
11,139
150' 200'
63 55
132 112
252 213
511 440
787 675
1,496 1,260