Mixing Valves; Closed System/Thermal Expansion - John Wood JW6 F307 Installation And Operating Manual

HOT WATER
OUTLET
FLUE COLLAR
CAPPED FOR REAR
FLUE USE (OPTIONAL)
AQUASTAT
TEMPERATURE
CONTROL
CENTER OF
BLAST TUBE
NON-COMBUSTIBLE
FLOOR
Figure 7 Plumbing Connections (Center/Rear Flue)

Mixing Valves

Water heaters are intended to produce hot water. Water
heated to a temperature which satisfies space heating, clothes
washing, dish washing, and other sanitizing needs can scald
and cause permanent injury upon contact. Short repeated
heating cycles caused by small hot-water uses can cause
temperatures at the point of use to exceed the water heater's
temperature setting by up to 11C° (20F°).
Some people are more likely to be permanently injured by
hot water than others. These include the elderly, children, the
infirm and the physically/mentally disabled. Table 3 shows the
approximate time-to-burn relationship for normal adult skin.
National plumbing code requirements limit the temperatures of
certain fixtures in the home. Local codes may have additional
requirements. In addition to these requirements, if anyone
using hot water in your home fits into one of these groups,
then you must take special precautions. In addition to using
the lowest possible temperature setting that satisfies your
hot water needs, a means such as a Mixing Valve, should
be used at the hot water taps used by these people or at the
water heater. Mixing valves are available at plumbing supply
or hardware stores. Consult a Qualified Installer or Service
Agency. Follow mixing valve manufacturer's instructions for
installation of the valves (see Figure 8). Before changing the
factory setting on the thermostat, read the "Water Temperature
Regulation" section in this manual.
VACUUM
COLD WATER
BREAKER
SHUT-OFF
T&P VALVE
COLD INLET AND
DRAIN VALVE
COMBINATION
150 TO 300mm
(6 TO 12")
– 14 –
TEMPERED
POTABLE WATER
NON-TEMPERED
WATER SUPPLY
MIXING VALVE
Figure 8 Suggested Plumbing Connections For Mixing
Valve Installation

Closed System/Thermal Expansion

Water supply systems may, because of code requirements
or such conditions as high line pressure, among others, have
installed devices such as pressure reducing valves, check
valves, and back fl ow preventers. Devices such as these
cause the water system to be a closed system. As water is
heated, it expands (thermal expansion). In a closed system
the volume of water will grow when it is heated. As the volume
of water grows there will be a corresponding increase in water
pressure due to thermal expansion. Thermal expansion can
cause premature tank failure (leakage). This type of failure is
not covered under the limited warranty. Thermal expansion
can also cause intermittent Temperature-Pressure Relief Valve
operation: water discharged from the valve due to excessive
pressure buildup. This condition is not covered under the
limited warranty. The Temperature-Pressure Relief Valve is
not intended for the constant relief of thermal expansion. A
properly sized thermal expansion tank must be installed on
all closed systems to control the harmful effects of thermal
expansion. Contact a local plumbing service agency to have
a thermal expansion tank installed.
Important: Do not plug or remove the temperature and
pressure relief valve.
COLD-WATER
SHUT-OFF
INLET
VALVE
NON-TEMPERED
WATER RETURN