GAS SUPPLY
Safe operation of unit requires properly
sized gas supply piping (See TABLE F).
Gas pipe size may be larger than the
heater connection.
An internal gas pressure regulator is required
if upstream pressure exceeds 6 oz. (10.5"
water column), an intermediate gas
pressure regulator, of the lockup type,
MUST
be installed.
Installation of a union is suggested for ease
of service.
Install a manual main gas shutoff valve with
test plug, outside the appliance gas
connection and before the gas valve, when
local codes require.
A trap (drip leg) should be provided in the
inlet of the gas connection to the unit.
HIGH ALTITUDE APPLICATIONS
Atmospheric pressure decreases as the height
above sea level increases. At any altitude above
sea level, a cubic foot will contain less gas than a
cubic foot at sea level. Thus, the heating value of a
cubic foot of fuel gas will decrease as height above
sea level increases. Specific gravity of a gas with
respect to sea level also decreases with altitude.
These changes in heating value and specific
gravity tend to offset each other. However, as
elevation above sea level is increased, there is
less oxygen per cubic foot of air. Therefore,
heat input rate should be reduced in an
appliance above 2000 feet. Ratings should
be reduced at the rate of 4 percent for each
1000 feet
above sea level.
WATER CONNECTIONS
L o c h i n v a r
D E S I G N E R
’
S G U I D E E F F I C I E N C Y
+
W A T E R H E A T E R
6 1 5 - 8 8 9 - 8 9 0 0
1 5
(TABLE H) – INLET GAS PRESSURE REQUIREMENTS
NAT. GAS
LPG
MAX. (INCHES-WATER COLUMN)
10.5
”
w.c.
13
”
w.c.
MIN. (INCHES-WATER COLUMN)
4.7
”
w.c.
8
”
w.c.
EXAMPLE OF
HIGH ALTITUDE
APPLICATIONS
For example, if a unit’s
input is 200,000 Btu/hr
at sea level, the rated
input at 4000 feet of
elevation can be
calculated by derating
input 4% per 1000 feet
above sea level.
[Btu/hr Input]
[1.00 - (Elevation/
1000 ft. x 0.04)] =
Btu/hr Input at
specified elevation.
[200,000][1.00 -
(4000 ft./1000 ft. x
0.04)] = Btu/hr Input
4000 ft. elevation.
[200,000][0.84] =
168,000 Btu/hr Input
at 4000 ft. elevation.
(TABLE G) – GAS SUPPLY PIPE SIZING
Length of Pipe In Straight Feet
Nominal Iron
Pipe Size, Inches
10
20
30
40
50
60
70
80
90
100
125
150
175
200
369
256
205
174
155
141
128
121
113
106
95
86
79
74
697
477
384
328
292
267
256
246
210
200
179
164
149
138
1,400
974
789
677
595
543
502
472
441
410
369
333
308
287
2,150
1,500
1,210
1,020
923
830
769
707
666
636
564
513
472
441
4,100
2,820
2,260
1,950
1,720
1,560
1,440 1,330
1,250
1,180
1,100
974
871
820
6,460
4,460
3,610
3,100
2,720
2,460
2,310 2,100
2,000
1,900
1,700
1,540
1,400
1,300
11,200
7,900
6,400
5,400
4,870
4,410
4,000 3,800
3,540
3,300
3,000
2,720
2,500
2,340
23,500 16,100 13,100 11,100 10,000
9,000
8,300 7,690
7,380
6,870
6,150
5,640
5,130
4,720
Maximum capacity of pipe in thousands of BTU’s per hour for gas pressures of 14” Inches Water Column (0.5 PSIG) or less and a total
system pressure drop of 0.05 Inch Water Column (Based on NAT GAS, 1025 BTU’s per Cubic Foot of Gas and 0.60 Specific Gravity).
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