Water Heater Sizing And Specifi Cations; Sizing Tankless Water Heaters - Bosch Greentherm T9800 SEC 160/199 Applications Manual

6 | Greentherm T9800 SE(C) 160/199
3 Water heater sizing and specifi cations
This section describes the water heaters available from Bosch Thermotechnology
Corp. and provides a general overview to the specifi cations of each particular
model. More detailed information is contained in the installation manuals. Download
manuals at www.bosch-climate.us.

3.1 Sizing tankless water heaters

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.
Sizing by Chart

Measure the flow rates at each fixture that will be used simultaneously and
add them together. If only one application will be used at a time measure
each fixture and use the maximum flow rate observed.

Using a known volume container, record several fill times. Perform the
calculation below to determine the flow rate (a one gallon fill time of 30
seconds is 2.0 gallons per minute (GPM):
Flow rate (GPM) =

Using a thermometer, measure the incoming water temperature. For
reference, see average ground water temperature map. Subtract 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.
EXAMPLE:

Required flow rate of 2.0 GPM at a 65˚F rise.

Refer to the graphs on page 10.
See Table 1 for multiple fi xture possibilities and hot water fl ow rates at given inlet
water temperatures with a water heater set point temperature of 120°F.
Data subject to change
Volume (gallons)
sec
x
60
min
Fill time (sec)
WA WA
MT MT
ND ND
OR OR
SD SD
ID ID
WY WY
NE NE
NV NV
UT UT
CO CO
CA CA
NM NM
AZ AZ
Figure 1 Average ground water temperatures
Application Manual
VT VT
NH NH H
MA MA
MN MN
NY NY
WI WI
MI MI
NJ
PA PA
IA IA
OH OH
DE
IN IN
IL IL
MD
WV WV VA VA
KS KS
KY KY
MO MO
NC NC
TN TN
SC SC
OK OK
AR AR
GA GA
MS MS
AL AL
LA LA
TX TX
FL FL
06.2017 | Bosch Thermotechnology Corp.
ME ME
RI
A A
CT
˚F
77˚
72˚
67˚
62˚
57˚
52˚
47˚
42˚
37˚