Tank Loading - Bosch 520PN Applications Manual

Applications Manual

5.3 Tank loading

Refer to drawings 13.2 and 13.3 on pages 32 and 33.
Tank loading pairs tankless water heaters with storage
tanks to maximize peak ow for high demand applications.
A tank load system, because of the added storage, can
provide a high peak ow with fewer tankless units and
lower installed cost.
These guidelines should be followed to maximize system
output:
f
Ensure flow through each water heater is between
3.5-5.0 gpm.
f
Isolation valves or boiler drains should be installed to
facilitate descaling in applications with hard water.
f
For best performance, plumb the system or configure
the tank to draw cold supply water into the water
heater during hot water use.
f
Maintain a 20 degree temperature difference between
tankless set-point and desired tank temperature.
f
Do not use a cascading kit in a tank loading
application.
f
When multiple tankless water heaters are used, the
total equivalent length of piping to each unit should
be kept roughly equal. A reverse return piping scheme
is recommended to equalize flow through each water
heater.
f
For tank temperature settings above 120° F, the Therm
C 1210 ESC is recommended. Other high capacity
Therms including the 830 ES, 940 ES/ESO, C 950 ES
and C 1050 ES can be used, but a high temperature
kit (part 7736500074) is required for each. In these
applications a thermostatic mixing valve is required.
Tank Loading Loop Pressure Drop at 4GPM (Feet of Head)
10 ft
Pipe
¾
" Type L Copper 0.48
1" Type L Copper 0.14
1.25" Type L Copper 0.06
1.5" Type L Copper 0.03
2" Type L Copper 0.01
Source: 2009 International Plumbing Code
* Calculations based on 120°F Set-point temperature, 107°F shower temperature, 2.5 GPM showerhead ow rate, 1.5 GPM sink ow rate,
adequate water pressure and gas supply. Variation from these parameters may alter performance. GPM shown is the hot water ow rate
at 120°F Set-point temperature.
Bosch Thermotechnology Corp.
90 45 Tee
Elbow Elbow Branch
0.1 0.03 0.15
0.04 0.02 0.07
0.02 0.01 0.04
0.01 <0.01 0.02
<0.01 <0.01 0.01
THERM/GREENTHERM Tankless Water Heaters | 9
Pressure drop vs. ow*
C 1210 ES / ESC,
# of
Units
C 1050 ES, C 950 ES
1 40 feet of head @ 4gpm
2 40 feet of head @ 8gpm
3 40 feet of head @ 12gpm
4 40 feet of head @ 16gpm
5 40 feet of head @ 20gpm
6 40 feet of head @ 24gpm
7 40 feet of head @ 28gpm
8 40 feet of head @ 32gpm
9 40 feet of head @ 36gpm
10 40 feet of head @ 40gpm
11 40 feet of head @ 44gpm
12 40 feet of head @ 48gpm
13 40 feet of head @ 52gpm
14 40 feet of head @ 56gpm
15 40 feet of head @ 60gpm
16 40 feet of head @ 64gpm
17 40 feet of head @ 68gpm
18 40 feet of head @ 72gpm
19 40 feet of head @ 76gpm
20 40 feet of head @ 80gpm
21 40 feet of head @ 84gpm
22 40 feet of head @ 88gpm
23 40 feet of head @ 92gpm
24 40 feet of head @ 96gpm
EXAMPLE:
Sizing a pump for a 4GPM tank loading DHW system with a
1050ES and a 20 ft total loop length.
Head Loss Loop Component
39.00 ft 1050es (See Fig.1, page 7)
1.00 ft 20 ft of ¾ copper
0.80 ft 8 x ¾" 90 elbows
+ 0.30 ft 2 x ¾" Tees (branch)
41.10 ft Minimum Pump Head at 4.0 gpm
Once the loop head loss has been calculated, use the
pump manufacturer's performance curves to select the
proper potable water circulator at the required ow rate.
940 ES, 940 ESO, 830 ES
32 feet of head @ 4gpm
32 feet of head @ 8gpm
32 feet of head @ 12gpm
32 feet of head @ 16gpm
32 feet of head @ 20gpm
32 feet of head @ 24gpm
32 feet of head @ 28gpm
32 feet of head @ 32gpm
32 feet of head @ 36gpm
32 feet of head @ 40gpm
32 feet of head @ 44gpm
32 feet of head @ 48gpm
32 feet of head @ 52gpm
32 feet of head @ 56gpm
32 feet of head @ 60gpm
32 feet of head @ 64gpm
32 feet of head @ 68gpm
32 feet of head @ 72gpm
32 feet of head @ 76gpm
32 feet of head @ 80gpm
32 feet of head @ 84gpm
32 feet of head @ 88gpm
32 feet of head @ 92gpm
32 feet of head @ 96gpm
Data subject to change