lp-83 Rev. 006 Rel. 005 Date 12.18.17
10
F. Potable Expansion Tank
A potable hot water expansion tank may be required to offset heated
water expansion. If there is a back flow preventer or any other type
of no return or check valve in the system a thermal expansion tank IS
MANDATORY. The expansion tank must be sized for the entire water
volume of the hot water system. A weeping relief valve indicates the
need for an expansion tank. See the Typical Expansion Tank example in
the Piping section for details.
G. Pressure Drop Sizing For Circulator
The boiler circulator flow rate must meet the requirements found in
the water heater specifications, Part 2, this manual, or the published
ratings cannot be achieved. The following flow chart below represents
the pipe run, water heater, and heat exchanger ONLY and does not
include any flow checks, zone valves, or friction loss through the boiler.
That resistance must be added to the value found in the following
chart.
Pressure Drop for Pipe Length of 1” Copper,
Six 90
o
Elbows, and One Tee
Pipe Size
20’
30’
40’
50’
60’
6 GPM
8.63
8.93
9.23
9.53
9.8
7 GPM
11.3
11.77
12.24
12.7
13.1
10 GPM
10.25
11.1
11.95
12.8
13.66
12 GPM
11.3
13.2
14.1
15
16
14 GPM
15.3
16.4
17.5
18.6
19.8
Pressure Drop for Pipe Length of 1 1/4” Copper,
Six 90
o
Elbows, and One Tee
Pipe Size
20’
30’
40’
50’
60’
20 GPM
10.9
11.7
12.6
13.4
14.3
22 GPM
14
15
16
17
18
24 GPM
16.2
17.5
18.8
20.1
21.5
28 GPM
20.4
22
23.6
25.2
26.8
Table 7 - Pressure Drop through 1” and 1 1/4” Copper
H. Applications
Figure 3 - Mixing Valve Installation
Figure 4 - Expansion Tank Application
Figure 5 - Installation with High Efficiency Boiler
NOTES:
1. Minimum pipe size should match connection size. Upsize pipe
accordingly if greater flow is required.
2. A thermal expansion tank suitable for potable water must be
sized and installed within this piping system between the backflow
preventer and the cold water inlet.
3. All circulators should have an integral flow check.
4. Drains and check valve between the heating appliance and water
heater will assist in purging air from system.
5. This drawing is meant to demonstrate system piping only. The
installer is responsible for all equipment and detailing required by
local codes. In Massachusetts, you must install a vacuum relief valve
per 248 CMR.
6. Mixing valve application is optional, but recommended to help
prevent scalding. See Part 3, Section E for more information.