Table of Contents
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Topics in this section
• Pressure Relief Valve Requirements
• Temperature - PRV Requirements
• Typical Installations
• Piping Diagram for Basic Installations
• Piping Diagram for Multiple Unit Installations
• Connect the Water Heater to the Water
Supply
• Plumbing Checklist
An approved pressure relief valve (PRV)
(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 PRV and do not install any
reducing fittings or other restrictions in the
PRV 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 PRV and the water heater.
MUST DO
• The PRV 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 PRV must be rated up to 150 psi and to at
least the maximum BTU/hr of the appliance.
• The discharge from the PRV should be
individually piped to the ground or into a drain
system per local codes.
• The PRV must be manually operated once a
year to check for correct operation.
• The PRV is installed near the tankless hot
water outlet according to the manufacturer's
instructions. DO NOT place any other type
valve or shut off device between the PRV and
the water heater.
Water discharged from the
WARNING
PRV could cause severe
burns instantly or death from scalds.
Demand Duo™ R-Series (REC) Installation and Operation Manual
• If a PRV 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 PRV.
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 PRV and the water
heater.
• DO NOT pipe T&P Relief valve and/or PRV
together into a common pipe.
MUST DO
• The T&P 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 T&P Relief valve must be rated up to 150
psi and to at least the maximum BTU/hr of the
appliance.
• The discharge from the T&P Relief valve
should be individually piped to the ground or
into a drain system to prevent exposure or
possible burn hazards to humans or other
plant or animal life. Follow local codes. Water
discharged from the relief valve could cause
severe burns instantly, scalds, or death.
• The T&P Relief valve must be manually
operated once a year to check for correct
operation.
33
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