Bosch Greentherm C1050ES & C950ES Venting Limitations

The Bosch Greentherm C1050ES and the Bosch Greentherm C950ES gas tankless water heaters have minimum and maximum venting lengths for the exhaust and intake air.  Please review the specifications below for the two heaters and the size, material and lengths that can be used.

Vent options
The Greentherm C1050ES & C950ES must comply with the following material for exhaust and intake air.

PP common vent
PP twin pipe
PVC schedule 40 ANSI/ASTM D1785
PVC-DWV ANSI/ASTM D2665
CPVC schedule 40 ANSI/ASTM F441
ABS-DWV schedule ANSI/ASTM D2661

The Greentherm C1050ES & C950ES have many different ways they can vent such as horizontal or vertical and can use different types of material for venting and intake air.  There is the Polypropylene up and out concentric vent kit, Polypropylene common vent system if you are cascading more than one unit and up to 4 units, PVC Concentric vent kit, you can do a twin pipe PVC vent, etc.

Maximum vent lengths for exhaust, intake air and use of elbows  for the Greentherm C1050ES & C950ES are listed below:

PP Common Venting Systems for Cascaded Units

New for the Greentherm C 950 ES and C 1050 ES, and the Therm C 1210 ES and C 1210 ESC, is a common venting system of polypropylene pipe for up to four appliances. Offered in either a side by side or back to back configuration, the kits allow for a single vent pipe for all units. Combustion air must be taken from the room for multiple units common vented.  A 3" PVC 90 degree elbow would want to be placed on either the left or right air intake hole for the combustion air to keep anything from falling into the heater.  This is mandatory for commercial applications, with multiple units installed and that the multiple units are common vented with either the side by side or back to back venting option.  All other applications such as residential, single units, etc. must take the combustion air from the outside using 3" PVC or 3" dia PP pipe.  Please refer to the installation manual for the Bosch tankless water heater for the combustion air requirements for the heater. 

Side by side with horizontal termination (left),

back to back with vertical termination (right)



The new polypropylene pipe (PP) common venting system features different kits for cascaded units of 2, 3 or 4 units.  Kits would have to be ordered as needed:

Kit A - side by side, units #1 & #2 (2 heaters) (7736501100)

Kit B - side by side, units #3 & #4 (1 heater) (7736501254)

Kit C - back to back, units #1 & #2 (2 heaters) (7736501253)

Kit D - Extension back to back, units #3 & #4 (2 heaters) (7736501252)

There are also additional 6" diameter PP venting pieces available.  There are additional:

Horizontal Termination Dia 6"  (7736501117)

Vertical Termination Dia 6"  (7736501119)

Extension rigid straight pipe 20" Dia 6"  (7736501137)

Extension rigid straight pipe 40" Dia 6"  (7736501135)

Extension rigid straight pipe 80" Dia 6"  (7736501133)

Rigid 90 degree elbow Dia 6"  (7736501132)

For example:

Say you were common venting and cascading 4 units side by side and venting up through the roof then you would want 1 - Kit A for units #1 & #2, 1 - Kit B for unit #3 and then 1 - Kit B for unit #4.  You would also then need 1 - 90 degree elbow, how many extra feet of extension straight pipe and then the vertical termination.