Gas Line Requirements; Measuring Gas Pressure - Noritz NR50-OD Service Manual

Gas Line Requirements

All Noritz Tankless Water Heaters must be provided with a sufficient supply of gas in order to function
properly. An undersized gas line could result in under heated water temperatures and an error code
displayed on the operation panel. To verify a properly sized gas line, follow the below procedures. The
gas line must provide at least the minimum stated pressure at the maximum firing rate. If the unit is being
supplied gas from other that a dedicated line, it is recommended that the other appliances be turned on to
ensure an adequate supply is available for the unit.
Gas Pressure
Size the gas line according to total btuh demand
of the building and length from the meter or
regulator so that the following supply pressures
are available even at maximum demand:
NCC199/841 Series
NR50-OD
NRC111/842 Series
NR66/531 Series
NR71/631 Series NR98/NC199/751 Series
Natural Gas Supply Pressure
Min: 4" WC
Max: 10.5" WC
LP Gas Supply Pressure
Min: 8" WC
Max: 14" WC

Measuring Gas Pressure

In order to check the gas supply pressure to the unit, a
tap is provided on the gas inlet. Remove the hex head
philips screw from the tap, and connect a manometer
using a silicon tube.
In order to check the gas manifold pressure, a pair of
taps are provided on the gas valve inside the unit.
The pressure can be checked either by removing the hex
head philips screw and connecting a manometer with a
silicon tube, or by removing the 1/8" NPT screw with an
allen wrench and connecting the appropriate pressure
gauge.
Sample Gas Line
Noritz Gas Water Heater
(see "Maximum Performance" table below)
Outlet E
Clothes Dryer
(35,000 Btuh)
10'
Outlet C
Section 4 Section 3 Section 2
5' 5' 5'
5'
Outlet D
10'
Gas Fireplace
(25,000 Btuh)
Maximum Performance (btuh)
Natural Gas
NR50-OD
Meter
NR66/N-0531S Series
NR71/N-0631S Series
NR98/NC199/N-0751M Series : 199,900 btuh
NCC199/N-0841MC Series
NRC111/N-0842MC Series
NR111/NC250/N-0931M Series : 250,000 btuh
NC380/N-1321M Series
Gas Meter
Select a gas meter capable of supplying the entire
btuh demand of all gas appliances in the building.
Gas Connection
Do not use piping with a diameter smaller than
NR111/NC250/931 Series
NC380 Series/N-1321M Series
the inlet diameter of the water heater.
Natural Gas Supply Pressure
Min: 5" WC
are rated for max Btuh of the heater (see below).
Max: 10.5" WC
LP Gas Supply Pressure
Min: 10.5" WC
Max: 14" WC
Use only approved gas piping materials.
Barbecue
(50,000 Btuh)
Outlet A
10'
5'
Section 1
10'
5'
Outlet B
Gas Range Stove
(65,000 Btuh)
: 120,000 btuh
: 140,000 btuh
: 180,000 btuh
: 199,900 btuh
: 199,900 btuh
: 380,000 btuh
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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
Outlet A: 45' (Use 50'), 50,000 Btuh requires 1/2"
Outlet B: 40', 65,000 Btuh requires 1/2"
Section 1: 45' (Use 50'), 115,000 Btuh requires 3/4"
Outlet C: 30', 35,000 Btuh requires 1/2"
Section 2: 45' (Use 50'), 150,000 Btuh requires 3/4"
Outlet D: 25' (Use 30'), 25,000 Btuh requires 1/2"
Section 3: 45' (Use 50'), 175,000 Btuh requires 1"
Outlet E: 25' (Use 30'),
180,000 Btuh requires 3/4" (NR71 Series)
140,000 Btuh requires 3/4" (NR66 Series)
120,000 Btuh requires 3/4" (NR50 Series)
Section 4: 45' (Use 50'),
355,000 Btuh requires 1-1/4" (NR71 Series)
315,000 Btuh requires 1-1/4" (NR66 Series)
295,000 Btuh requires 1-1/4" (NR50 Series)