Standing pilot ignition
78% average efficiency
Pressure relief valve include
Vertical venting: 5" double-wall type B-vent pipe. Minimum vent height: 6'. Minimum rise 12" before elbow. Horizontal venting: AQ4 power vent accessory required.
- Power Vent Option illustrating the side wall vent option that allows horizontal venting up to 100' and elimination of the chimney. Use the AQ4 Power Vent AQ4 for the Bosch GWH 425 HN (Part #AQ4).
Download Installation Manual (PDF) 
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|
Model/Product
|
Energy Factor
|
Annual Cost
to Operate*
|
Annual
Savings¹
|
Annual
Savings²
|
|
635 ES/ESO
|
0.80
|
$250
|
$110
|
$151
|
|
425 HN/HNO
|
0.80
|
$266
|
$95
|
$135
|
|
425 EF
|
0.78
|
$273
|
$88
|
$129
|
|
40-gallon tank
|
0.59
|
$361
|
|
|
|
75-gallon tank
|
0.53
|
$410
|
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| Technical Specifications |
| |
| |
GWH 425 PN |
| Power Input |
NG: 31,000-117,000 Btu
LP: 31,000-117,000 Btu |
| Minimum Flow to Activate (gpm) |
0.5 gallons per minute (gpm) |
| Flow Rates |
90° F rise / 2.1 gpm
77° F rise / 2.4 gpm
65° F rise / 2.9 gpm
55° F rise / 3.4 gpm
45° F rise / 4.2 gpm |
| Energy Factor |
NG: .69
LP: .79 |
| Thermal Efficiency |
NG: 78%
LP: 78% |
| Dimensions |
H: 22¾" W: 16¾" D: 8½" |
| Weight |
33 lbs. |
| Modulating Gas Valve |
Yes |
| Ignition |
Standing Pilot |
| Optional Accessory |
Power vent for horizontal venting (AQ4) |
| Installation Specifications |
| Gas Connection |
¾" Male NPT |
| Water Connections |
½" Male NPT |
| NG Gas Pressure |
Minimum: 7" WC
Maximum: 14" WC |
| LP Gas Pressure |
Minimum: 11" WC
Maximum: 14" WC |
| Water Pressure |
Minimum: 30 PSI
Maximum: 150 PSI |
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Installation Manual