Water Heater Sizing & Specifi Cations; Sizing Tankless Water Heaters - Bosch C 1210 ES Applications Manual

THERM Tankless Water Heater Applications Manual
6 Water Heater Sizing & Specifi cations
This section describes the water heaters available from Bosch
Thermotechnology Corporation and provides a general overview to
the specifi cations of that particular model. More detailed
information is contained in the installation manuals. Download
these manuals at www.BoschPro.com.

6.1 Sizing tankless water heaters

Defi nitions
Major applications (2 GPM or more): Washing machine, bath tub,

shower nozzle
Minor applications(2 GPM or less): Low fl ow shower head, bath-

room sink, kitchen sink
Rule of thumb sizing
The tables below provide a general rule of thumb when sizing for
most residential applications. For commercial applications or for a
more detailed sizing method, use the Sizing by Chart instructions
below in conjunction with the charts on the next page.
Rule of Thumb Sizing
Model Number Number of Major
Applications
C 1210 ES/ESC
C 1050 ES
940 ES/ESO
830 ES
660EF/EFO
520 HN/PN
330 PN
Sizing by Chart
Measure the fl ow rates at each fi xture that will be used

simultaneously and add them together. If only one application will
be used at a time measure each fi xture and use the maximum fl ow .
rate observed
Using a known volume container, record several fi ll times. Per-

form the calculation below to determine the fl ow rate (a one
gallon fi ll time of 30 seconds is 2.0 gallons per minute (GPM):
Volume (gallons)
Flow rate (GPM) =
Fill time (sec)
Using a thermometer, measure the incoming water temperature.

For reference, see average ground water temperature map. Sub-
tract this temperature from the desired hot water temperature to
get the degree rise. If the desired hot water temperature is 120F
and incoming temperature is 55F, the desired degree rise is 65F.
BOSCH THERMOTECHNOLOGY CORPORATION
Number of Minor
Applications
3 1
2 1
2 0
1 2
1 1
1 0
0 1
sec
x
60
min
Figure 1 Average ground water temperatures
EXAMPLE:
• Required fl ow rate of 2.0 GPM at a 65˚F rise.
• Refer to the graphs on the following page.
• Since the demand is above the 330 PN capacity, this application
would require a 520 HN/PN gas tankless water heater.
•
Data subject to change without notice | 01.2011
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