- 22 -
2-9 PRESSURE RELIEF VALVE
• Install an approved pressure relief valve with every gas water heater installation.
• The pressure relief valve shall conform to the following requirements.
Relief Valves and Automatic Gas Shutoff Devices for Hot Water Supply Systems ANSI Z21,
22. This pressure relief valve shall activate with the pressure of 150PSI.
• The pressure relief valve shall be installed in the outgoing hot water supply line according to
the manufacturer's instruction.
• No valves or shut off device shall be placed between the relief valve and the unit.
The discharge from the pressure relief valve shall be piped to the ground or into the drain
system to prevent possible burns to humans or animals. Hot water discharged from the relief
valve may cause severe scalding instantly and even death.
• Do not cap the relief valve and do not install any depressurizer or restriction device in the relief
line.
• Manually operate the pressure relief valve at least once a year to check if it functions properly.
2-10 ELECTRICAL CONNECTION
MWH-180EX must be electrically grounded in accordance with local codes or in the absence
of local codes with the most recent edition of the National Electrical Code, ANSI/NFPA 70. In
Canada, all electrical wiring to the MWH-180EX should be in accordance with local codes
and the Canadian Electrical Codes, CSA C22.1 Part 1. Do not rely on the gas or water piping
to ground the metal parts of the water heater.
Warning
• Label all wires prior to disconnection when servicing controls. Wiring errors can cause
improper and dangerous operation.
Verify proper operation after servicing.
Field wiring to be performed at time of appliance installation.
• Completely turn off the power before starting the work.
Do not turn the power on until the electric wiring is finished and all work is completed.
Otherwise electric shock or personal injury may result.
Caution
