Pressure Relief Valve - Rheem RTGH-RH11DV Use And Care Manual

Figure 29 – Pressure Drop through the Heat Exchanger
∆T = 77°F (25°C)
Number
Flow Rate
of units
(GPM)
1 5
2 10
Table 21 – Recommended Water Pipe Size
NOTE: The above pipe sizes are recommended based on maximum water velocity of 5 ft/s and maximum water temperature of 140°F.
▪ E. 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 in-
jury, or death.
This water heater must be provided with an approved 150 psi (1,034 kPa),
¾" ASME HV Valve that must be installed on the DHW outlet line (See Figure
30). The 150 psi Pressure Relief Valve must be installed on the DHW supply
line to ensure a compliant installation and safe operation.
This water heater has a high-temperature shut-off switch built in as a stand-
ard 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 ASME
rating plate on the water heater.
RECOMMENDED WATER PIPE SIZE
Water
Pipe Flow Rate
Velocity
Dia. (in) (GPM)
(ft/s)
3.75 3/4
4.22 1
∆T = 45°F (7.2°C)
Flow Rate Pipe
(GPM) Dia. (in)
9 3.61 1
18 3.21 1 1/2
∆T = 35°F (1.6°C)
Water
Flow Rate
Velocity
(GPM) Dia. (in)
(ft/s)
11 4.64
23 4.13
Figure 30 – Pressure Relief Valve
49
Pipe
1
1 1/2
AP18733 REV. 3.2.17