Water Heater Sizing & Speci Cations; Sizing Tankless Water Heaters - Bosch 520PN Applications Manual

1 0 | THERM/GREENTHERM Tankless Water Heaters
6 Water Heater Sizing &
Speci cations
This section describes the water heaters available from
Bosch Thermotechnology Corp. and provides a general
overview to the speci cations of each particular model.
More detailed information is contained in the installation
manuals. Download manuals at www.bosch-climate.us.

6.1 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
f
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.
f
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):
Volume (gallons)
Flow rate (GPM) =
Fill time (sec)
Hot water ow rate at 120°F Set Point temperature
Model
77°
C 1210
ES /
9.8
ESC
C 1050
ES
8.5
C 950
ES
7.7
940 ES
/ ESO
7.7
830 ES
6.7
520 HN
/ PN
4.3
330 PN
2.7
Simultaneous Showers
Data subject to change
sec
x
60
min
72° 67°
8.8 8.0
7.6 6.9
6.9 6.2
6.9 6.2
6.0 5.4
3.8 3.5
2.4 2.2
Sink Faucet
WA WA
MT MT
OR OR
ID ID
WY WY
NV NV
UT UT
CO CO
CA CA
NM NM
AZ AZ
Figure 2 Average ground water temperatures
f
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:
f
Required flow rate of 2.0 GPM at a 65ÝF rise.
f
Refer to the graphs on page 10.
f
Since the demand is above the 330 PN capacity, this
application would require a 520 HN/PN gas tankless
water heater.
Inlet temperature (°F)
62° 57° 52°
7.3 6.7 6.2
6.3 5.8 5.4
5.7 5.2 4.9
5.7 5.2 4.9
5.0 4.6 4.2
3.2 2.9 2.7
1.9 1.7
2.0
Applications Manual
ND ND
MN MN
NY NY
WI WI
MI MI
SD SD
PA PA
IA IA
NE NE
OH OH
IN IN
IL IL
VA VA
WV WV
KS KS
KY KY
MO MO
NC NC
TN TN
SC SC
OK OK
AR AR
GA GA
MS MS
AL AL
TX TX LA LA
FL FL
47° 42°
5.8 5.4
5.0 4.7
4.5 4.2
4.5 4.2
4.0 3.7
2.5 2.3
1.6 1.5
Bosch Thermotechnology Corp.
ME ME
VT VT
NH NH H
RI
MA MA A A
CT
NJ
˚F
DE
77˚
MD
72˚
67˚
62˚
57˚
52˚
47˚
42˚
37˚
37°
5.1
4.4
4.0
4.0
3.5
2.2
1.4