Combustion Air Requirements For a Gas Tankless Water Heater
The combustion air requirements only apply to indoor
installations and where air is drawn from within the room where
the water heater is installed. The 250SX, 2400E are the
only Bosch tankless water heaters that have a separate air
intake that allows for air to be drawn from the outside. The RTG-53DV GT-199DV RTG-74DV are the only Rheem tankless water heaters that allow for air to be drawn from the outside. For all other indoor
installations, the amount of combustion air should be a minimum
volume of 50 cubic feet per 1,000 Btu/hr rated input.
| Model |
|
Combustion Air Requirements in Sealed Room |
Size of openings if cannot meet combustion air
requirements in
sealed room |
|
BTU's |
Cubic Feet |
Square ft
(w/ 8ft ceiling) |
Size of openings (air
direct from outside) |
Size of openings (air from within house) |
| Bosch 38B |
40,000 |
2,000 |
250 |
10 sq inches
(i.e. 3" x 4") |
40 sq inches
(i.e. 6" x 7") |
|
Bosch 1000P |
74,500 |
3,725 |
466 |
19 sq inches
(i.e. 4” x 5”) |
75 sq inches
(i.e. 9” x 9”) |
Bosch 1600P/125B,
Bosch 1600H/125HX |
117,000 |
5,850 |
730 |
29 sq inches
(i.e. 5"x6") |
117 sq inches
(i.e. 11" x 11") |
Bosch 1600F
125FX |
130,000 |
6,500 |
813 |
33 sq inches
(i.e. 6” x 6”) |
130 sq inches
(i.e. 12” x 11”) |
|
Rheem RTG-53PV |
145,000 |
7,250 |
906 |
36 sq inches
(i.e. 6” x 6”) |
145 sq inches
(i.e. 12” x 12”) |
|
Rheem RTG-53DV |
145,000 |
Combustion air requirements do not apply to
the 2400E/250SX when air is drawn from the outside through
the intake vent. |
|
Bosch 2400E/250SX - no air intake vent |
175,000 |
8,750 |
1,100 |
< 44 sq inches
(i.e. 6"x7") |
175 sq inches
(i.e. 13" x 13") |
|
Bosch 2400E/250SX
2400EO/250SXO with air intake vent |
175,000 |
Combustion air requirements do not
apply to the 2400E/250SX when air is drawn from the outside
through the intake vent. |
|
Rheeem RTG-74PV |
199,900 |
10,000 |
1,250 |
50 sq inches (i.e. 7” x 7”) |
200 sq inches
(i.e. 14” x 14”) |
|
Rheem RTG-74DV,
RTG-74X,
GT-199DV |
199,900 |
Combustion air requirements do not apply to
the RTG-74DV and GT-199DV when air is drawn from the outside
through the intake vent. |
Note: A Gas tankless water heater cannot be installed in a mobile home, bedroom, bathroom, or any other confined living space normally kept closed.
Note: The above information is meant as guidance.
Always consult your installation manual and/or local code
requirements before any actual installation.
If the gas water heater is installed in an area smaller than what the combustion
call for, then the installer must make special provisions for combustion air in
the form of two openings, each one within 12" of the top and 12" of the bottom
of the space, having a total free area of 1 square inch per 1,000 Btu/hr of
rated input if the air is taken from inside the house. This requirement reduces
to 1 square inch per 4,000 Btu/hr if the air is taken from the outside.
Additional Factors to Consider
Gas Venting Requirements
Gas Line Sizing Requirements
Gas Combustion Air Requirements
|
