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Gas Pressure Adjustment Locations
Electronic Ignition Gas Valves
GAS PRESSURE ADJUSTMENT
Honeywell VR8340 (Heater Models 268A and 408A)
GAS PRESSURE ADJUSTMENT
Robertshaw 7000 BDER (Heater Model 268A)
Figure 14. Robertshaw 7000 DERHC (Heater Model 408A)
APPROVED
GAS
PRESSURE
ADJUSTMENT
UNCONTROLLED DOCUMENT IF PRINTED
Pipe Sizing for Gas Connection
These capacities shown below based on using SCH
40 black iron pipe. For capacities using other materials,
consult local code.
Maximum Equivalent Pipe Length (ft) (m)
Natural Gas 1000 BTU/FT
Specific Gravity @ 0.5 in WC Pressure Drop
Propane Gas 2500 BTU/FT
Specific Gravity @ 0.5 in WC Pressure Drop
3/4"
Model
N
P
N
15
35
50
268A
(4.6)
(10.7)
(15.2)
15
20
408A
*
(4.6)
(6.1)
* A 3/4" gas line can be used for up to 5' (1.5 m) maximum length from the gas valve
in addition to the sediment trap.
Table I.
Gas Pipe Sizing
Flow Rate
Model
Pipe Size
268A
1-1/4"–1-1/2"–2"
408A
1-1/4"–1-1/2"–2"
* When flow rates exceed maximum GPM an external auxiliary bypass valve is
required. See external bypass valve section for details.
Table J.
Min/Max Flow Rates
Figure 15. Bronze Header Water Flow
3
0.60
3
1.53
1"
1-1/4"
1-1/2"
N
P
N
P
125
210
480
445
(38.1)
(64.0)
(146.3)
(135.6)
55
95
225
215
(16.8)
(29.0)
(68.6)
(65.5)
Max. GPM
Min. GPM (lpm)
(lpm)
25 (95)
100 (378)
40 (151)
100 (378)
F10637-2
P
480
(146.3)
15
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