Bosch Gas Tankless Water Heaters and Tank Loading Applications

Global Pro Tankless Supply is always trying to make it easier to figure out the right Bosch tankless water heater that is designed for the right application.  A tank load system, because of the added storage, can provide a high peak flow with fewer tankless units and lower installed cost. This will cover the basics for a tank loading application that will enable the user to have more domestic hot water and can also be set up for heating applications.  The Bosch gas tankless models such as the C1210ESC/C1210ES/C1050ES/C950ES/940ES and 830ES are all capable and designed to work with a tank loading applications.  Tank loading can be done using a standard tank heater as a storage tank or an indirect tank such as the Bosch SST Indirect Storage Tanks.

Many of the tank loading applications range from small singular tank loading to commercial tank loading such as for hotels and Inns.  Please see the diagram below for a basic design of a tank loading application.

For all the different tank loading applications please review the Bosch Applications Manual or call Global Pro Tankless Supply at 866-289-4652.

Replacement Heat Exchangers Now on Global Protankless Supply

Global Protankless Supply is now carrying the replacement heat exchangers for all the Bosch gas tankless water heaters.  The heat exchangers are made of high quality copper. Below is a list of all the heat exchangers and their current part numbers.  Older part numbers are also listed as part numbers have changed over the years.

Bosch Therm C1210ES / C1210ESC Heat Exchanger Part 8705406419 (87054064190 or 8-705-406-419-0).  This part is also the replacement Heat Exchanger for the older Bosch ProTankless 920ES and 920ESC condensing tankless water heaters.

Bosch Greentherm C1050ES-LP / C950ES-LP (Liquid Propane) Heat Exchanger Part 8738704026 (87387040260 or 8-738-704-026-0).

Bosch Greentherm C1050ES-NG / C950ES-NG (Natural Gas) Heat Exchanger Part 8738704117 (87387041170 or 8-738-704-117-0).

Bosch Therm C1050ES-LP / C950ES-LP (Liquid Propane) Heat Exchanger Part 8705406421 (87054064210 or 8-705-406-421-0).

Bosch Therm C1050ES-NG / C950ES-NG (Natural Gas) Heat Exchanger Part 8738721270 (87387212700 or 8-738-721-270-0).

Bosch Therm 940ES / 830ES Heat Exchanger Part 8738701985 (87387019850 or 8-738-701-985-0). This part is also the replacement Heat Exchanger for the Therm 940ESO, Bosch ProTankless 715ES, Bosch AquaStar 2700ES and 2400ES and the Bosch Evolution 500.  Older part numbers were 8705406422, 87054064220, 8-705-406-422-0, 8705406356, 87054063560, 8-705-406-356-0.

Bosch ProTankless 635ES / 635ESO Heat Exchanger Part 8705406285 (87054062850 or 8-705-406-285-0).  This part is also the replacement Heat Exchanger for the Bosch AquaStar 2400E, 2400EO, 250SX and 250SXO tankless water heaters.

Bosch Therm 520 Heat Exchanger Part 8705406386 (87054063860 or 8-705-406-386-0).  The Bosch Therm 520 Heat Exchanger Part 8705406386 is the replacement heat exchanger for all Bosch Therm 520PN and 520HN tankless water heaters and for all Bosch ProTankless 425PN and certain Bosch ProTankless 425HN (with serial numbers starting 686 and higher) tankless water heaters. It is also the replacement heat exchanger for all Bosch AquaStar 1600P and 1600H tankless water heaters. This heat exchanger replaces the obsolete 8705406275 (87054062750, 8-705-406-275-0) heat exchanger.

Bosch ProTankless 425 Heat Exchanger Part 8705406380 (87054063800 or 8-705-406-380-0).  The Bosch 425 Heat Exchanger is the replacement heat exchanger for the following Bosch ProTankless water heaters: 425EF, 425HN (with serial numbers starting 685 and lower) and 425HNO and the following Bosch AquaStar tankless water heaters: 125B, 125BO, 125BL, 125X, 125HX, 125FX.  This heat exchanger will also work with the following Bosch WR400 series tankless water heaters: WR400-1KV1P23S3100, W400KD5 P23S3100T2, WR400-3K V1B23S3100, WR400-7K V1G23S3195, WR430-3K VM1E23S3190 and WR430-3K VM1E23S3195.  Older part numbers were 8705406235, 87054062350, 8-705-406-235-0.

Bosch Tankless Water Heaters with New Built-In External Water Filters

Bosch Thermotechnology is always improving the gas-fired tankless water heaters and has recently improved all the sealed combustion tankless water heaters and have added a new hydraulic block on the bottom of all the units that incorporates a new built in external water filter.

The Bosch Greentherm C950ES and Bosch Greentherm C1050ES condensing heaters were designed with the new hydraulic block and external water filter built in.  The Bosch Therm C1210ES/ESC, Bosch 940ES and the Bosch 830ES have recently had the new hydraulic block and external water filter added.  After Serial number beginning with "301" will have the built in external water filter.

Built-in External Water Filter

All of the older Bosch "Therm" models before serial number 301 had the external water filter, part #8703035356 and was sold as an accessory.

Please contact Global Protankless Supply with any questions at 866-289-4652.

Phasing out of Bosch Therm 940ESO Outdoor Unit

Bosch is phasing out the Therm 940ESO model tankless water heater in Natural Gas, Part Number 7738000001 and Liquid Propane, Part Number 7738000002.

Bosch will continue to still make the Bosch Therm 940ES NG & LP tankless water heaters. The Bosch Therm Outdoor Kit (BTOK) will be sold as an accessory for outdoor installations.

The Phase out of the Bosch Therm 940ESO outdoor unit will be immediate. Please see the list below for model numbers, color changes by manufacturing date and BTOK model numbers.

Bosch Therm 940ES NG - #7703311076
Bosch Therm 940ES LP - #7703411073
(Gray Models, FD prior to FD420 - White Models, on or after FD420)

BTOK Outdoor Kit - Gray #7709003913
BTOK Outdoor Kit - White #7736502448

Please call Global Protankless Supply at 866-289-4652 for further questions or ordering.

Using Bosch Tankless for Domestic Hot Water Recirculation

Bosch tankless water heaters can be used in recirculation applications and there are many different set ups for this such as direct recirculation and indirect recirculation.  Certain models of the Bosch tankless water heaters are approved for direct recirculation and are listed below.  Please be aware that the heat exchanger warranty of 15 years will be reduced to 3 years for direct recirculation.  This is stated in the warranty section of the installation manual.   All of the Bosch tankless water heaters can be set up for an indirect recirculation application in conjunction with a mini tank, recirculation pump and aquastat as described in the image below. The warranty for recirculation through an indirect mini-tank and not directly through the heater is 15 years.

Bosch tankless water heaters approved for direct recirculation:
Bosch Therm C1210ES
Bosch Therm C1210ESC (Commercial Unit)
Bosch Greentherm C1050
Bosch Greentherm C950
Bosch Therm 940ES
Bosch Therm 830ES

Diagram for Recirculation Application:
(This schematic is for illustration only and must not be used for actual installation without appropriate engineering and technical advise from a properly licensed professional in the locality where the installation is made).

Bosch Tankless Water Heaters Used for Solar Thermal Applications

Certain models of the Bosch tankless water heaters are approved and designed for using Solar Thermal. Solar Thermal applications should be set up in conjunction with an indirect tank to maintain a more consistent temperature but the heater can be used for direct solar preheated water.  The maximum temperature for the solar preheated water into the Bosch tankless water heater is 140 degrees F.  The Bosch tankless water heaters that are approved for Solar preheated water are listed below:

Bosch Therm 830ES
Bosch Therm 940ES
Bosch Greentherm C950ES
Bosch Greentherm C1050ES
Bosch Therm C1210ES
Bosch Therm C1210ESC

Bosch Therm Intelligent Cascading Kit

The Bosch Therm Intelligent Cascading Kit part number 7709003962 connects the Bosch Therm tankless water heaters together in an intelligent cascading setup.  Up to 24 Bosch Therm tankless water heaters can be connected together in intelligent cascading to deliver more GPM for each heater cascaded.

The Bosch Therm Intelligent Cascading Kit is designed to work with the following Bosch tankless water heaters:  C1210ESC, C1210ES, C1050ES, C950ES, 940ES, 940ESO, 830ES.

Please refer to the installation manual for proper installation of the Bosch Therm Intelligent Cascading Kit.

Installing the Bosch Therm High Temperature Kit #7736500074

The Bosch Therm High Temperature Kit (7736500074) allows the maximum temperature of the Bosch tankless water heater to be raised from its normal maximum of 140 degrees F up to 180 degrees F.

The Bosch Therm High Temperature Kit is designed to work with the following Bosch tankless water heaters:  Greentherm C1050ES, Therm C10505ES, Greentherm C950ES, Therm C950ES, C800ES, Integra 500, 940ES, 940ESO, Evolution 500 and 830ES.

The Bosch Therm High Temperature Kit is not designed to work with the Bosch Therm C1210ESC or the C1210ES.

The Bosch Therm High Temperature Kit is bascially some instructions and a couple Jumpers.  The installation of the kit is very easy.  There are 2 small jumpers that will be inserted on the control board in the Bosch tankless water heater.

Installing the Bosch Therm High Temperature Kit:
*Make sure power to the unit is TURNED OFF!
1.  First remove the front cover of the heater.
2.  Then remove the screws holding the control unit on the bottom of the heater.
3.  Once the control unit is detached then you can access the back of the control unit and you will see a square cutout on the back and some pins where the jumpers will be inserted.  The pins are labeled JP5, JP6, JP7, JP8 and JP2 on the bottom.  Insert the 2 small jumpers from the high temp kit into pins JP7 & JP8.
4.  Double check connections and then screw the control unit back into place and put the front cover on.
5.  Turn the power back on and the heater should default to 120 degrees F.  You will now be able to raise and lower the temperature on the unit from 100 - 184 degrees F.  Please take into consideration that when the heater is set at say, 180 degrees that the unit will only be able to flow about 1.5 - 3 GPM depending on the heater you have.  The higher the temperature the lower flow you will get.

Replacement Heat Exchanger #87054064220 for Bosch Protankless 715ES

The replacement heat exchanger for the Bosch Protankless 715ES has a new part number of 87054064220. This part number has changed from the original part number of 8705406356.  The heat exchanger part number 87054064220 is also the replacement for Bosch Therm 830ES, 940ES, 940ESO and the Bosch Evolution 500.

This replacement heat exchanger is also good for the retail heaters Bosch 2400ES/2700ES.

Service Bulletins for Bosch Therm Gas Tankless Water Heaters

Bosch has a series of service bulletins for the new model Bosch Therm tankless water heaters.  These service bulletins can be very helpful with installation questions and when having an issue to troubleshoot the heater.

Please remember to be safe when working on a gas fired appliance.  Service bulletins are helpful but you can also contact Bosch technical support for help at 800-642-3111.

Link to:
Service Bulletins for Bosch Therm Units

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

Bosch Wireless Remote Control TSTAT2

The Bosch Wireless Remote Control TSTAT2 for the Bosch Therm and Protankless models 635ES / 635ESO / 715ES / C800ES / C920ES / C920ESC / C830ES / C940ES / C940ESO / C950ES /    C1050ES / C 1210ES / C 1210ESC / Integra 500 / Evolution 500 allows you to program your Bosch tankless gas water heater to a comfortable and safe temperature from around your home from a distance of up to 98 ft.

The TSTAT2 remote is particularly useful if you own a jacuzzi or hot tub that requires a hotter water temperature than you normally desire for regular shower use.

Please note that the electrical control board of the older Bosch 635ES / 635ESO heaters must be removed and opened in order to install the wireless receiver circuit board to enable the use of the TSTAT2 Wireless Remote Control.

The Newer Bosch models, 715ES / C800ES / C920ES / C920ESC / C830ES / C940ES / C940ESO / C950ES / C1050ES / C 1210ES / C 1210ESC / Integra 500 / Evolution 500 tankless water heaters have been redesigned to make the installation of the wireless receiver circuit board much easier. The circuit board is basically a plug and play unit.

The TSTAT2 controls the temperature of your water heater and does not have a reset button.   If the heater has an error then a code will be on the display of the heater and the user has to go to the heater to reset it from there and should document the error and then see if it returns after resetting.

The TSTAT2 Wireless Remote Control for Bosch 635ES / 635ESO / 715ES / C800ES / C920ES / C920ESC / C830ES / C940ES / C940ESO / C950ES / C1050ES / C 1210ES / C 1210ESC / Integra 500 / Evolution 500 features the following:

• LCD displays temperature, error codes and functions
• Temperature measured in °C or °F
• Low battery level indicator
• 98 feet user range
• Alkaline AA LR6 2x1.5V battery power 915 MHz
• Security lock function
• IP X6 Protection
• Priority function - temperature cannot be modified by other user interface when water is running

Don't forget to periodically change the two AA batteries in your Bosch wireless TSTAT2 thermostat as they will certainly corrode over time. The batteries in TSTAT2 thermostats that are kept in bathrooms will corrode faster than in other less humid environments, such as kitchens. Your batteries should be checked yearly for any signs of corrosion and replaced every five years in any case.

New Bosch Tankless Universal Control Board

Bosch has released a new Universal Control Board (part number 87072073680) for their "World Two" tankless water heaters.

The board comes with three jumpers and instructions as to where to place those jumpers to make the board model-specific.

One jumper specifies if the heater is a 175,000 BTU or a 199,000 BTU appliance, another jumper specifies the gas type - NG or LP, and another jumper specifies if the heater has a surface-mounted outlet temperature sensor or is using a newer immersed sensor that is included on some recent production heaters.

Additionally, the world two universal control board is able to automatically determine if it is being used on a condensing or non-condensing tankless water heater.

This universal control board can be used on the following Bosch tankless water heaters for both natural gas and propane:

• C1050ES, C950ES, 940ES, 940ESO, 830ES
• C800ES, 715ES
• Integra 500, Evolution 500
• AquaStar 2700ES, AquaStar 2400ES

Call us at 866.289.4652 for more details or to place your order.

Gas Conversion of Pro Gas Tankless Water Heaters

Some of the Bosch Professional gas tankless water heaters can be converted from one gas type to the next, i.e. from Natural Gas (NG) - Liquid Propane (LPG) and also from LPG - NG.  The Gas Conversion Kit, part #8719002176 includes a jumper for placement on the control board, a set of instructions for calibrating the gas and air mix and also some stickers to be placed on the heater stating it has been converted. 

The tools required for the gas conversion are:

• Flat and Phillips Screwdrivers
• #40 torx driver
• Digital CO2 Gas Combustion Analyzer
• This procedure must be performed by a licensed gas technician

The Bosch Professional Non-condensing heaters such as the 940ES/940ESO/830ES/715ES/635ES and the Evolution 500 CAN be converted using the gas conversion kit.

All of the Bosch Therm condensing heaters such as the C1210ESC/C1210ES/C1050ES/C950ES/C800ES and Integra 500 CANNOT be converted as the units have a special plate built into the burner tray.  This extra plate in the burner tray was designed and instlled to give the heater the ability to be installed at higher elevations up to 8000'.

Also the Bosch Therm 660EF/660EFO/520PN/520HN/425HN/425EF/330PN CANNOT be converted as they are not designed at all for gas conversion.

Bosch Therm Tankless Product Number Changes

Recently Bosch has changed their naming strategy for the Bosch Therm line up of Tankless Water Heaters. Previously, the Bosch part numbers reflected the flow rate at a 45 degree F temperature rise; now the part numbers reflect the flow rate at a 35 degree F temperature rise.

So, for example, the legacy Bosch Pro 920ES is now the Bosch Therm  C 1210ES. This means that this heater can produce 9.2 GPM of hot water at a 45 degree F rise and 12.1 GPM at a 35 degree F rise.

This naming change was done, so it seems, to align Bosch with an emerging industry de facto standard of showing the flow rate at a 35 degree F temperature rise. In reality, showing the flow rate at a 45 degree F temperature rise made more sense as a 45 degree F temperature rise is more realistic average across the US. However, with other manufacturers advertising their heaters 35 degree F flow rate, it appeared that their tankless water heaters had a higher flow rate (which was of course not true).

So, now Bosch's published flow rates allow for easier comparisons to those of other manufacturer's heaters.

Bosch did make some upgrades to the new models, so actually the newer heaters have more capabilities than their older legacy heaters. More about those details in later blog entries...

Here is a brief listing of the name changes:

• Old: Bosch Pro 920ES  |  New: Bosch Therm C 1210ES
• Old: Bosch Pro 920ESC  |  New: Bosch Therm C 1210ESC
• Old: Bosch Pro 800ES  |  New: Bosch Therm C 1050ES
• Old: Bosch Pro 715ES  |  New: Bosch Therm 940ES & Bosch Therm 940ESO
• Old: Bosch Pro 425HN  |  New: Bosch Therm 520HN
• Old: Bosch Pro 425PN  |  New: Bosch Therm 520PN
• Old: Bosch Pro 260PN  |  New: Bosch Therm 330PN

The part numbers for the Bosch Electric whole-house and point-of-use tankless water heaters did not change, nor did the Ariston Pro Ti names change.

Call us for pricing on any of the new Bosch Therm Tankless Water Heaters at 866.289.4652.

Global ProTankless Supply