Bosch GWH425EF Natural Gas Tankless

The 425 EF has all the durability and performance of the 425 HN, with an added bonus—a built-in power vent. This makes the unit ideally suited for households requiring horizontal, through-the-wall venting only.

4" sealed single-wall stainless steel or galvanized pipe of 26 minimum gauge. Maximum length 15' with 2 elbows. Maximum 4 elbows allowed. Must terminate horizontally. Horizontal vent terminator accessory (Part #FXHOOD KIT) required and sold separately.

Electronic Ignition

Built-in Power Vent

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Frequently Asked Questions

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Parts Diagram

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Power Input	NG: 28,000 - 130,000 Btu LP: 28,000 - 125,000 Btu
Minimum Flow Rate to Activate	0.5 gallons per minute (gpm)
Flow Rates	90° F rise / 2.3 gpm 75° F rise / 2.7 gpm 65° F rise / 3.3 gpm 55° F rise / 3.8 gpm 45° F rise / 4.6 gpm
Energy Factor	NG: .78 LP: .81
Thermal Efficiency	NG: 80% LP: 82%
Dimensions	29¾"h x 18¼'w x 8¾”d
Weight	44 lbs.
Ignition	Electric
Accessories	Horizontal Vent Terminator - FXHOOD (FXHOOD required)
Modulating Gas Valve	Yes
Life Expectancy	20+ years
Installation Specifications
Gas Connection	¾" Male NPT
Water Connection	¾" Male NPT
NG Gas Pressure LP Gas Pressure	Minimum: 7" WC Maximum: 14 " WC Minimum: 11" WC Maximum: 14" WC
Water Pressure	Minimum: 18 PSI Maximum: 150 PSI
Electrical Supply	120 volts/1.2 amps (plugs in)
Vent Size	4" (single-wall stainless or galvan

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