Bosch ProTankless 425PN Heat Exchanger

The Bosch ProTankless 425PN Heat Exchanger Part 8705406386 (87054063860, 8-705-406-386-0) is the current replacement heat exchanger for allBosch ProTankless 425PN tankless water heaters.

Please note that the original heat exhanger for all Bosch ProTankless 425PN tankless water heaters was 8705406275 (87054062750, 8-705-406-275-0). This part is now obsolete and has been replaced by the 8705406386 heat exchanger.

Replacement Heat Exchanger for Bosch 830ES/940ES/940ESO and Evolution 500

The Bosch 940ES, 940ESO, 830ES and the Bosch Evolution 500 Heat Exchanger Part 8705406422 is the replacement heat exchanger for all Bosch Therm 940ES, 940ESO, 830ES and the Bosch Evolution 500 tankless water heaters.

This part is also the replacement Heat Exchanger for the Bosch Aquastar 2400ES and 2700ES tankless water heaters.

Bosch Therm External Water Filter

The Bosch External Water Filter (8703305356) replaces the internal water filter that comes with the heater. Having the water filter external means it is located under the Bosch Therm tankless water heater and is therefore easy to access and clean out. Odds are that if you do not install the external water filter then the internal water filter will not get regularly cleaned out as you would have to open the cover and remove the control board to get to the internal water filter, which is not very convenient.  It is recommended to clean the filter screen at least once a year for periodic maintenance.

The Bosch Therm External Water Filter is designed to work with the following Bosch Therm Tankless Water Heaters: C 1210 ESC, GWH C 920 ESC, C 1210 ES, GWH C 920 ES, C 1050 ES, GWH C 800 ES, C 950 ES, 940ES, 940ESO, GWH 715 ES, and 830ES.

This accessory is not included with these heaters and is highly recommended.

The Bosch External Water Filter is included with the Bosch Integra 500 and Bosch Evolution 500 water heaters.

The Bosch External Water Filter is NOT compatible with the new Bosch Greentherm C950ES and Greentherm C1050ES tankless water heaters.

Replacement filter screens part 8700507059 are available for the Bosch External water filter.  Please call us at 866-289-4652

Webstone Isolation Valve Set #44443WPR

The Webstone Isolator EXP E2 Isolation Valve Kit #44443WPR (Lead-Free) for All Bosch Gas Tankless Water Heaters comes with separate hot and cold isolation valves and a Pressure Relief Valve. The NEW Webstone isolation valve set #44443WPR replaces the older set of 44443PR.  Easy two-step installation of your tankless water heater with unsurpassed safety, features and benefits. This is a complete inlet/outlet valve system that provides everything you need for a secure installation, including full port testing and flushing of the system with easy-to-install union connections.

Convenient two-step color coded union connections.

Easy quarter turn ball valve operation

Full port throughout entire valve body

Individually controlled full port drain outlet

Ready to use for flushing or descaling  (Please see the Whitlam Descale Kit)

3/4" outlet for pressure relief valve

1/2" water supply adapters included (except when purchased with the 3/4" Bosch C1210ES/C1050ES/940ES/800ES heaters as they are not needed)

Heavy forged brass construction

Conforms to NSF 61-9

Allows for one man full diagnostic testing of heater unit

This product is intended for use with all of our indoor and outdoor tankless water heaters.

The Webstone 44443WPR Isolation valves are a set of Hot & Cold Full Port Forged Brass Ball Valves w/ Hi_Flow Hose Drains & Pressure Relief Valve Outlet 3/4" IPS Union x 3/4" IPS (500 WOG) & PRESSURE RELIEF VALVE (150 PSI/200K BTU) ISO 9001.

Descaling Bosch Gas Tankless Water Heaters

All of the Bosch gas tankless water heaters both in natural gas (NG) and Liquid Propane (LP) should be descaled now and then on a periodic basis depending on the quality of the water in your area.  Some towns have low mineral content while others are very hard.  Scale is basically mineral deposits in the water that pass through the copper tubing of the heat exchanger and after heating up they stick to the insides of the copper piping and over long periods of time will restrict the flow of water through the heat exchanger causing issues and overheating. 

Global Pro Tankless Supply sells a Flow-Aide Descaling Kit that allows the user to flush the Bosch tankless water heater with not much work involved and eliminates the scale built up in the heater.

The Flow-Aide Descaler Kit comes with everything you need to quickly dissolve water scale, lime, rust, and other water formed deposits, restoring efficiency to all Bosch gas tankless water heaters.  This descaling kit will also work for all other gas tankless water heaters, boilers, etc.

Flow Aide System Descaler is a non-toxic concentrate which is certified to NSF/ANSI 60 for use as a cleaner in potable water systems. Flow-Aide is the perfect descaling solution to keep your Tankless Water Heater in good operation. Combining Flow-Aide with one of our Isolation Valve Kits (Service Valves) will make the descaling process quick and easy!

Flow-Aide is: Non-Corrosive, Non-Toxic, Fully Biodegradable*, Safe to Handle, Zero V.O.C.

IMPROVE EQUIPMENT EFFICIENCY: Water scale deposits are a significant cause of heat transfer loss, along with the subsequent increase in energy costs. In fact, even a thin layer of scale (1/32") can cause a 30% increase in the cost to operate that piece of equipment. Keeping the heating passages free of mineral deposits significantly improves efficiency, conserves energy, extends the useful life of the equipment, and saves you time & money.

The Flow-Aide Descaling Kit includes the following:

1 - 3.5 Gallon Bucket
1 - 350 GPH Pump
2 - 5 Foot Rubber Hoses
1 - Quart Flow-Aide

There is also the Flow-Aide Descaling Kit PLUS which includes the Isolation Valve Kit (Service Valves).  We also sell additional quarts and gallons of the Flow-Aide Solution.

 

Bosch Therm 520HN NG & LP Tankless Water Heater

The new Bosch Therm 520HN comes set for either NG (Natural Gas) or LP (Liquid Propane).  The 520HN has a hydro ignition and is a naturally drafting heater and requires no power to operate.  This unit is basically for 1 major application at a time such as 1 shower at a time.  The Bosch 520 HN Needs to be vented vertically with a 5" B-vent up through the roof for a minimum of 6' to the raincap.  If the heater has to be vented out the sidewall then you must use the AQ4 Powervent kit and this kit would require 110V power.  The gas connection at the bottom of the heater is a standard 3/4" connection.

The new Bosch Therm 520HN is a direct replacement for many of the older model heaters.  Below is a list of the units that the 520HN would replace.  Please keep in mind to always be aware of gas line sizing and the length of the gas line run.

The Bosch Therm 520HN could replace:

Bosch 1600P or 1600H: (If either one of these units was vented horizontally out the sidewall with the AQ4 powervent kit then that same AQ4 powervent kit can be used for the new Bosch Therm 520HN)

Bosch Aquastar 125B, 125X, 125HX, 425PN or the 425HN: (If any of these units was vented horizontally out the sidewall with the AQ1 powervent kit then that AQ1 powervent kit WILL NOT work for the new Bosch Therm 520HN.  You would need to install the new AQ4 powervent kit for the new Bosch Therm 520HN)

ELM Le Blanc 170VP or 125VP:  (If either one of these units was vented horizontally out the sidewall with the AQ1 powervent kit then that AQ1 powervent kit WILL NOT work for the new Bosch Therm 520HN.  You would need to install the new AQ4 powervent kit for the new Bosch Therm 520HN)

The Bosch Therm 520HN is a direct replacement for the older tankless water heaters listed above but you still always want to make sure and refer to the installation manual and follow the gas line sizing chart and venting requirements.  Please also refer to local code for all other restrictions and approvals.

Bosch Therm 520PN NG & LP Tankless Water Heater

The new Bosch Therm 520PN comes set for either NG (Natural Gas) or LP (Liquid Propane).  The 520PN has a standing pilot and is a naturally drafting heater and requires no power to operate.  This unit is basically for 1 major application at a time such as 1 shower at a time.  The Bosch 520 PN Needs to be vented vertically with a 5" B-vent up through the roof for a minimum of 6' to the raincap.  If the heater has to be vented out the sidewall then you must use the AQ4 Powervent kit and this kit would require 110V power.  The gas connection at the bottom of the heater is a standard 3/4" connection.

The new Bosch Therm 520PN is a direct replacement for many of the older model heaters.  Below is a list of the units that the 520PN would replace.  Please keep in mind to always be aware of gas line sizing and the length of the gas line run.

The Bosch Therm 520PN could replace:

Bosch 1600P or 1600H: (If either one of these units was vented horizontally out the sidewall with the AQ4 powervent kit then that same AQ4 powervent kit can be used for the new Bosch Therm 520PN)

Bosch Aquastar 125B, 125X, 125HX, 425PN or the 425HN: (If any of these units was vented horizontally out the sidewall with the AQ1 powervent kit then that AQ1 powervent kit WILL NOT work for the new Bosch Therm 520PN.  You would need to install the new AQ4 powervent kit for the new Bosch Therm 520PN)

ELM Le Blanc 170VP or 125VP:  (If either one of these units was vented horizontally out the sidewall with the AQ1 powervent kit then that AQ1 powervent kit WILL NOT work for the new Bosch Therm 520PN.  You would need to install the new AQ4 powervent kit for the new Bosch Therm 520PN)

The Bosch Therm 520PN is a direct replacement for the older tankless water heaters listed above but you still always want to make sure and refer to the installation manual and follow the gas line sizing chart and venting requirements.  Please also refer to local code for all other restrictions and approvals.