Bosch Appliances Model GWH 425 Measuring gas pressure, Water connections, Support all piping

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Installation instructions

3.8Measuring gas pressure

Connecting manometer

BShut off gas.

BRemove front cover and locate inlet gas pressure measuring point on the right side, see Fig. 15.

BLoosen screw from test point on the right side and connect manometer tube on test point.

Fig. 15 Gas pressure measuring point

AInlet tap

Static pressure test

BTurn gas supply back on.

BRecord static gas pressure reading on back page of manual.

Operating pressure test

BTurn on all hot water taps served by the water heater.

BRun high hot water flow rate.

BSet flow control knob fully clockwise.

BSet slide control to the right.

BRecord operating gas pressure reading on back page of manual.

Gas pressures lower than 5.7" W.C. for Natural Gas or 10.5" W.C. for LP Gas will result in insufficient degree rise to the hot water being used, and must be corrected. See Gas Line Sizing under chapter 3.7.

3.9 Water connections

When facing the heater, the ½” cold water inlet is on the bottom right and the hot water outlet is on the bottom left.

BInstall unions or the Webstone service valves when connecting plumbing to the water heater. This will facilitate any necessary cleaning and servicing.

Although water piping throughout your structure may be other than copper, we recommend that copper piping or suitably rated stainless steel flex line piping be used for at least three feet before and after the heater (follow local codes if more stringent). Never sweat any rigid piping directly to or beneath the water connections, damage can occur to the internal water valve from heating of the pipe. Plastics or other PEX type plumbing line materials are not recommended for connecting directly to the water heater. Keep water inlet and outlet pipes to no less than ½" (12.7mm) diameter to allow the full flow capacity.

It is recommended that all water piping below the heater be properly insulated to avoid heat loss.

If the cold and hot connections to the heater are reversed, the heater will not function. Be certain there are no loose particles or dirt in the piping. Blow out or flush the lines before connecting to the water heater. Full port valves should be installed on both the cold water supply and hot water outlet lines to facilitate servicing the heater (see Fig. 16). For installation on a private well system with the use of a pressure tank, the lowest pressure range setting recommended is 30-50 psi (2.07 and 3.45bar).

Connecting the pressure relief valve (PRV)

The pressure relief valve supplied with the heater must be installed at the time of installation. No valve is to be placed between the PRV and the heater. No reducing coupling or other restriction may be installed in the discharge line. The discharge line must be a minimum of 4” above a drain and installed such that it allows complete drainage of both the PRV and the line.

The location of the PRV must be readily accessible for servicing or replacement, and be mounted as close to the water heater as possible. See Fig. 16. To install the PRV, a suitable fitting connected to an extension on a “T” fitting can be sweated to the hot water line.

Support all piping.

Fig. 16 Plumbing connections and pressure relief valve shown with optional Webstone service valves

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Contents GWH-425-PN-N GWH-425-PN-L Index IndexOver heat prevention temperature limiter Water resistant GWH 425 PN specifications Technical dataAppliance details Appliance detailsGeneral rules to follow for safe operation Unpacking the GWH 425 PN heaterDimensions in Inches and mm Dimensions and installation clearancesProper location for installing your heater Installation instructionsHeater placement and clearances Installation instructionsScrews Incandescent particle tray Mounting HeaterAppliances located in confined spaces Combustion air requirementsVenting Existing interior masonry chimney Installation instructions Masonry chimneyGAS Connections Gas piping & connectionsFor Natural GAS Connecting the pressure relief valve PRV Connecting manometer Shut off gasMeasuring gas pressure Water connectionsOperation instructions For your safety read before operating your water heaterRecirculation application Operation instructionsTo turn off appliance Lighting instructionsTemperature adjustment knob Setting the water temperatureDraining water from heater Maintenance intervals Maintenance and serviceWater valve PilotMain burners Vent assemblyMineral scale build-up Operate the circulating pumpPilot lights, but goes out when button is released TroubleshootingIntroduction Pilot does not light Pilot goes out during or after hot water useBurners do not light with water flow Hot water temperature fluctuates at tapCheck for a clogged inlet water filter screen see chapter Water is too hot Noise when heater is runningWater is not hot enough Burners ignite without hot water flowBurners do not operate cleanly yellow flames when operating Protecting the environment Protecting the environmentSaving water resources Interior components and diagram parts list Interior components and diagram parts listInterior components Components Diagram Components diagramDescription Reference Parts listFifteen Year Limited Warranty Serial Number Bosch Group Bosch Water Heating Mad River ParkGas Pressure Reading Static Waitsfield, VT all rights reserved