lp-673 Rev. 000 Rel. 001 Date 8.30.18
22
F. Circulator Sizing
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
22.00
24.00
0
2
4
6
8
10
12
14
16
18
20
22
24
Pr
ess
ur
e
D
ro
p
(fe
et
o
f h
ea
d)
Flow Rate (GPM)
199 Pressure Drop Curve
199
Figure 14 - This chart represents heat exchanger pressure losses.
G. Pressure Relief Valve
Figure 15 - Pressure Relief Valve
An external pressure relief valve must be installed on this water heater.
When installing, observe the following guidelines. Failure to comply
with these guidelines can result in substantial property damage,
personal injury, or death.
This water heater must be provided with an approved 150 psi, ¾”
ASME HV Valve that must be installed on the DHW outlet line. The 150
psi Pressure Relief Valve must be installed on the DHW outlet line to
ensure a compliant installation and safe operation.
This water heater has a high-temperature shut-off switch built in as
a standard safety feature. Therefore, a “pressure only” relief valve
is required. DO NOT operate this water heater before the supplied
pressure relief valve is installed with sufficient relieving capacity in
accordance with the rating plate on the water heater.
Pressure relief valves must be installed as close to the water heater as
possible. No other valves should be placed between the pressure relief
valve and the appliance. DO NOT install a relief valve with a pressure
rating greater than 150 psi. This is the maximum allowable relief valve
setting for this water heater.
After installing the relief valve and filling and pressurizing the
system, test the operation of the valve by lifting the lever. Make
sure the valve discharges freely. If the valve fails to operate correctly,
replace it with a new relief valve. Ensure that the maximum BTU/H
rating on the pressure relief valve is equal to or greater than the
maximum input BTU/H rating of the combination water heater.
System Temperature Rise Chart
Model
Minimum
Pipe Size
20
o
F ∆T
30
o
F ∆T
40
o
F ∆T
Flow Rate (GPM)
Head (FT)
Flow Rate (GPM)
Head (FT)
Flow Rate (GPM)
Head (FT)
199
1 1/4”
18.9
14
12.6
6.5
9.5
4
Table 15 - Water Heater Flow Rates - Recommended Pumps - TACO 0013, Grundfos UP26-99BF
Model
Number of Units Cascaded
2
3
4
5
6
7
8
199
2”
3”
4”
Table 16 - Manifold Pipe Sizes in Inches – NOTE: The above pipe sizes are based on 20
o
F Delta and maximum water velocity between 5 - 6 ft/s
When installing a cascaded system, ensure the water heaters are the same model. Failure to do so will result in improper system operation,
wasted time, money, and possible property damage and personal injury. Such damages ARE NOT covered by product warranty.