Procedure for Programming The Wireless Remote TSTAT2

The Bosch Wireless Remote Control (TSTAT2) is used to remotely control the temperature of the Bosch Therm tankless water heater. The TSTAT2 does NOT have the ability to remotely reset the Bosch Therm hot water heater. Below is a more in depth procedure for installing the remote control.

The Bosch Wireless Remote Control (TSTAT2) is designed to work with the following Bosch Therm Tankless Water Heaters: C 1210 ESC, C 1210 ES, C 920 ESC, C 920 ES, C 1050 ES, C 800 ES, Integra 500, C 950 ES, 940ES, 940ESO, 715 ES, Evolution 500 and 830ES as well as the Bosch AquaStar 2700ES and 2400ES heaters.

TSTAT2 Remote Control Installation:

On the "heater" control panel, press and hold Program key while
pressing the ON/OFF button to ON.  Release program key when LCD
displays “188”.  LCD shows “P2”. If not, repeat previous step.

1. Press the + button on the heater to select "P3".  Press and hold Program 
key again for 1 sec.  LCD shows one number and one rotating digit. If not, 
repeat previous step.

The number represents the remote control which is to be registered, the
first remote control will be registered with number “0”, the second with
number “1” and so on.  The rotating digit shows that the electronics is 
expecting a registration and waiting for response from wireless remote.  
If the LCD fails to show a number and rotating digit after repeated attempts, 
double check the wire connections made in section 5.1.

2.  Hold wireless remote control in front of the control panel on the heater and
simultaneously press remote control buttons until the temperature indication 
is shown on the remote control LCD.

3.   Press ON / OFF button on the front of the heater to OFF position and then
back ON.

4.  Press buttons + or - on the remote to reach desired temperature.

New remote control is programmed.

To program a 2nd or 3rd remote to the same heater, follow the steps above and 
then after the remote is programmed you will be able to use the first or 2nd or 
3rd remote to raise or lower the temperature on the heater.  Please remember
the remotes cannot be used to reset the heater if an error code should appear.

Service Bulletins for Older Bosch Aquastar Gas Tankless Water Heaters

Bosch has a series of service bulletins for the older retail model Bosch Aquastar and also the compact models such as the 1600P & 1600H.  These service bulletins can be very helpful with installation questions and when having issues with the Bosch tankless water heater.

Service bulletins can help with fixing an issue or with servicing your Bosch tankless water heater.  Please keep in mind and be safe when working on a gas appliance.  You can also contact Bosch directly or have you service agent contact Bosch technical support at 800-642-3111.

Link to:
G3 Service Bulletins for GWH 2700 ES and GWH 2400 ES

CT Service Bulletins for GWH 1000 P, 1600 P, 1600 H

G2 Service Bulletins for GWH 2400 ES/ESO, 250SX/SXO

AquaStar 38B, 125 Series Gas Tankless

AquaStar VP Series Service Bulletins

 AquaStar 240FX Service Bulletins 

Bosch Aquastar 250SX/250SXO Water Valve with Engine

The Bosch Aquastar model 250SX/250SXO water valve with engine part number 8708505018 (old part number 8708505016) is the replacement watervalve for all Bosch Aquastar model 250SX/250SXO tankless water heaters.

This is also the replacement water valve for the Bosch Aquastar 2400E tankless water heater.

Bosch AquaStar 2400E / 2400EO / 250SX / 250SXO Heat Exchanger

The Bosch AquaStar 2400E / 2400EO / 250SX / 250SXO Heat Exchanger Part 8705406285 is the replacement heat exchanger for all Bosch AquaStar 2400E, 2400EO, 250SX and 250SXO tankless water heaters.

This part is also the replacement Heat Exchanger for the Bosch ProTankless 635ES and 635ESO tankless water heaters.

Bosch Wireless Remote Control TSTAT2

The Bosch Wireless Remote Control TSTAT2 for the Bosch AquaStar 2700ES / 2400ES / 2400E / 2400EO / 250SX / 250SXO 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 of the Bosch AquaStar 2700ES / 2400ES / 2400E / 2400EO / 250SX / 250SXO 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, 2700ES and Bosch 2400ES 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 2700ES / 2400ES /2400E / 2400EO / 250SX / 250SXO 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.

Freeze Protection for Bosch Gas Tankless Water Heaters

Most all of the Bosch gas tankless water heaters come with built in freeze protection.  The heaters listed below have built in freeze protection and are approved to be installed in some outside installations.

Our Bosch Outdoor Tankless Water Heaters (Bosch 2700ES with AQOK Outdoor Cap / Bosch 2400ES with AQOK Outdoor Cap/ 125BO / 425HNO / 2400EO / 250SXO) have built in freeze protection and are designed to handle an occasional overnight freeze. They plug directly into the wall and provide freeze protection down to 5 deg F above zero. In order for the freeze prevention kit to provide adequate protection,120V AC must always be supplied to the water heater.They are approved for use in the following areas:


Florida, Georgia, North Carolina, South Carolina, Alabama, Mississippi, Arkansas, Texas, Virginia (only in zip codes beginning with the first three digits 233-237), Arizona (in zip codes beginning with the first three digits 850-857 and 864), Oregon (in zip codes beginning with the first three digits 970-975), Washington (in zip codes beginning with the first three digits 980-986), California (except in zip codes beginning with the first three digits 935 or 961).

Installation instructions state that the water heaters must not be installed in a location where it may be exposed to prolonged freezing temperatures. If the heater must be left in a space which is likely to experience prolonged freezing temperatures, all water must be drained from the heater.  If precautions are not taken, resulting damage will not be covered under the warranty. NOTE: Use of agents such as anti-freeze is not permitted as they may cause damage to the water heater's internal components.  The freeze prevention will not protect plumbing outside the appliance from freezing. Precautions should be taken.

The Bosch 250SX/2400E/2400ES and 2700ES come with built in freeze protection and these units are for inside installation only.  The freeze protection helps the unit if it is installed on the inside of an outside wall where it may be cooler than normal.

Replacements for Bosch Tankless Heat Exchangers

Today we sold and shipped a replacement heat exchanger for a Bosch 125VP tankless water heater.

This customer told me that he loved his Bosch water heater and has had it for -- get this -- 20 years!

He told me that he has maintained it regularly with a descaling solution and that he loves his water heater! We breifly discussed the merits of purchasing a new Bosch tankless water heater, but he told me that he is very happy with the heater he has.

Global Pro Tankless Supply can supply customers with replacement heat exchangers for many of the older model tankless water heaters. Just give us a call and we can get you a quote on any of the following legacy Bosch AquaStar heaters:

Bosch AquaStar 38B
Bosch AquaStar 125B
Bosch AquaStar 125BL
Bosch AquaStar 125BS
Bosch AquaStar 125HX
Bosch AquaStar 125X
Bosch AquaStar 250SX
Bosch AquaStar 250SXO
Bosch AquaStar 240FX
Bosch AquaStar 80VP
Bosch AquaStar 125VP
Bosch AquaStar 170VP

Steve