State MHEW2-40R-035D - Manual (Page 6)

6
Water System Piping
Piping, fi ttings, and valves should be installed according to
the installation drawing (Figure 6). If the indoor installation
area is subject to freezing temperatures, the water piping
must be properly insulated.
The water supply pressure should not exceed 80 psi. If this
occurs, a pressure reducing valve with a bypass should
be installed in the cold water supply line. This should
be placed on the supply to the entire house in order to
maintain equal hot and cold water pressures.
IMPORTANT:
•
Heat must not be applied to the water fittings on the
heater as they may contain nonmetallic parts. If solder
connections are used, solder the pipe to the adapter
before attaching the adapter to the hot and cold water
fittings.
• Always use a good grade of joint compound and be
certain that all fittings are tight.
Piping Installation
1. Install the water piping and fittings as shown in Figure
6. Connect the cold water supply (3/4” NPT) to the
fitting marked “C”. Connect the hot water supply (3/4”
NPT) to the fitting marked “H”.
IMPORTANT: Some models may contain energy sav-
ing heat traps to prevent the circulation of hot water
within the pipes. Do not remove these inserts.
2. The installation of unions in both the hot and cold
water supply lines are recommended for ease of
removing the water heater for service or replacement.
3. Some local codes may require, and the manufacturer of
this water heater recommends, installing a mixing valve
or an anti-scald device in the domestic hot water line
as shown in Figures 7 and 8. These valves reduce
the point-of-use temperature of the hot water by mixing
cold and hot water and are readily available. Contact
a licensed plumber or the local plumbing authority for
more information.
4. If installing the water heater in a closed water system,
install an expansion tank in the cold water line as
specified under “Closed System/Thermal Expansion.”
5. Install a shut off valve in the cold water inlet line. It
should be located close to the water heater and be
easily accessible, but not located between the water
heater and expansion tank. Know the location of this
valve and how to shut off the water to the heater.
6. Install a temperature and pressure relief valve and
discharge line in the opening marked “T & P RELIEF
VALVE”. Install as specified under “Temperature and
Pressure Relief Valve.”
7. After piping has been properly connected to the water
heater, open the nearest hot water faucet and allow
the tank to completely fill with water. To purge the
lines of any excess air and sediment, keep the hot
water faucet open for 3 minutes after a constant flow
of water is obtained. Close the faucet and check all
connections for leaks.
Figure 8
Mixing Valve
Top Water Connections
Follow the mixing
valve manufacturer’s
instructions
Cold
Water
Inlet
Hot
Water
Outlet
Tempered
Water To
Fixtures
Mixing Valve
(Set To 120° F)
Tempered
Water to Fixtures
Hot
Water Out
Cold Water In
Set To 120° F Maximum
Mixing Valve
Follow The Mixing
Valve Manufacturer’s
Installation Instructions
Figure 7
Mixing Valve
Side Water Connections
In a closed system use a
thermal expansion tank.
Pressure
Reducing
Cold Water
Inlet
Cold Water
Inlet Valve
Hot
Water
Outlet
Union
Temperature And
Pressure Relief Valve
Drain Line
3/4 Inch ID
Minimum
Drain Pan
2-1/2 Inch Depth Maximum
1 Inch
Minimum
Figure 6
Water Piping Installation
Massachusetts:
Install a vacuum
relief in cold water
line per section 19
MGL 142.
Floor Drain
6” Maximum
Air Gap
Discharge Line
(Do not cap or plug.)