Table of Contents
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Topics in this section
• Pressure Relief Valve Requirements
• Temperature - PRV Requirements
• Connect the Water Heater to the Water
Supply
• Typical Installations
• Piping Diagram for Basic Installations
• Piping Diagram for Multiple Unit Installations
An approved pressure relief valve (preinstalled) is
required by the American National Standard
(ANSI Z21.10.3) for all water heating systems
and shall be accessible for servicing.
DO NOT
• Do not plug the relief valve and do not install
any reducing fittings or other restrictions in the
relief line. The relief line should allow for
complete drainage of the valve and the line.
• Do not place any other type valve or shutoff
device between the relief valve and the water
heater.
WARNING
Water discharged from the pressure relief valve
could cause severe burns instantly or death from
scalds.
MUST DO
• The relief valve must comply with the standard
for Relief Valves and Automatic Gas Shutoff
Devices for Hot Water Supply Systems ANSI
Z21.22 and /or the standard Temperature,
Pressure, Temperature and Pressure Relief
Valves and Vacuum Relief Valves, CAN1-4.4.
• The pressure relief valve must be rated up to
150 psi and to at least the maximum Btu/hr of
the appliance.
• The discharge from the pressure relief valve
should be piped to the ground or into a drain
system per local codes.
• The pressure relief valve must be manually
operated once a year to check for correct oper-
ation.
Demand Duo™ H-Series Installation and Operation Manual
•
The relief valve is installed near the tankless
hot water outlet.
INFORMATION
If a relief valve discharges periodically, this may
be due to thermal expansion in a closed water
supply system. Contact the water supplier or
local plumbing inspector on how to correct this
situation. Do not plug the relief valve.
Install the Temperature-Pressure Relief (T&P)
Valve according to these instructions.
The tank portion of this system is provided with a
combination T&P relief valve. For safe operation
of the water heater, the relief valve(s) must not be
removed from its designated point of installation
or plugged.
An approved T&P relief valve is required by the
American National Standard (ANSI Z21.10.3) for
all water heating systems, and shall be
accessible for servicing.
DO NOT
• Do not plug the T&P relief valve and do not
install any reducing fittings or other restrictions
in the relief line. The relief line should allow for
complete drainage of the T&P relief valve and
the line.
• Do not place any other type valve or shut off
device between the relief valve and the water
heater.
• Do not pipe T&P relief valve, pressure relief
valve, and/or condensate drain together into a
common pipe.
MUST DO
• The T&P valve must comply with the standard
for Relief Valves and Automatic Gas Shutoff
Devices for Hot Water Supply Systems ANSI
Z21.22 and /or the standard Temperature,
Pressure, Temperature and Pressure Relief
Valves and Vacuum Relief Valves, CAN1-4.4.
37
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