John Wood Atmospheric Gas (Standard) - Manual (Page 17)

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of the temperature and pressure relief valve (T & P)
or higher than normal water temperatures are the first
signs of thermosiphoning.
• The domestic hot water line from the water heater
should be vertical past any mixing valve or supply line to
the air handler to remove air bubbles from the system.
Otherwise, these bubbles will be trapped in the air
handler heat exchanger coil, reducing the efficiency.
• Do not connect the water heater to any system or
components previously used with non-potable water
heating appliances when used to supply potable water.
Some jurisdictions may require a backflow preventer in the
incoming cold water line. This may cause the temperature
and pressure relief valve on the water heater to discharge
or weep due to expansion of the heated water. A
diaphragm-type expansion tank suitable for potable water
will normally eliminate this weeping condition. Please
read and follow the manufacturer’s instructions for the
installation of such tanks.
Also see Water System Piping for additional instructions
on the safe and correct installation and operation of this
water heater.
TYPICAL MIXING VALVE INSTALLATION COMBINATION
SPACE HEATING/POTABLE WATER HEATING SYSTEM
MIXING
VALVE
HOT
WATER
OUT
UNIONS
IN
MUST BE VERTICAL TO
REMOVE AIR BUBBLES
DOMSETIC
HOT WATER
OUT
FLOW CONTROL
VALVE PUMP
OUT
COIL
AIR
HANDLER
TO
AIR
HANDLER
SHUT-OFF
VALVE
EXPANSION TANK
VACUUM
RELIEF
VALVE COLD WATER INLET
FIGURE 14.
Solar Installation
If this water heater is used as a solar storage heater
or as a backup for the solar system, the water supply
temperatures to the water heater tank may be in excess
of 120°F (48.9°C). A mixing valve or other temperature
limiting valve must be installed in the water supply line to
limit the supply temperature to 120°F (48.9°C).
NOTE: Solar water heating systems can often supply
water with temperatures exceeding 180°F (82.2°C) and
may result in water heater malfunction.
to the insulation to ensure that it is fully seated on the
T&P Relief Valve. Once seated, secure the insulation
with duct tape, electrical tape, or equivalent.
IMPORTANT: The insulation or tape should not block
or cover the T&P relief valve drain opening. Also, the
insulation or tape should not block or hinder access
to the manual relief lever (Figure 13B). Ensure
that a discharge pipe is installed into the T&P valve
discharge opening per the instructions in this manual.
4. Locate the hot water (outlet) & cold water (inlet) pipes
to the water heater.
5. Locate the slit running the length of a section of pipe
insulation.
6. Spread the slit open and slip the insulation over the cold
water (inlet) pipe. Apply gentle pressure along the length
of the insulation to ensure that it is fully seated around
the pipe. Also, ensure that the base of the insulation is
flush with the water heater. Once seated, secure the
insulation with duct tape, electrical tape, or equivalent.
7. Repeat steps 5 and 6 for the hot water (outlet) pipe.
8. Add additional sections of pipe insulation as needed.
T&P RELIEF VALVE
DRAIN LINE
T&P RELIEF
VALVE
MANUAL RELIEF
LEVER
T&P RELIEF VALVE INSULATION
FIGURE 13B.
Combination Space Heating/Potable
Water System
Some water heater models are equipped with inlet/outlet
connections for use with space heating applications. If this
water heater is to be used to supply both space heating
and domestic potable (drinking) water, the instructions
listed below must be followed.
•
Be sure to follow the manual(s) shipped with the air
handler system.
• This water heater is not to be used as a replacement
for an existing boiler installation.
• Do not use with piping that has been treated with
chromates, boiler seal or other chemicals and do not
add any chemicals to the water heater piping.
• If the space heating system requires water
temperatures in excess of 120°F (48.9°C), a mixing
valve or an anti-scald device should be installed per its
manufacturer’s instructions in the domestic (potable)
hot water supply to limit the risk of scald injury.
• Pumps, valves, piping and fittings must be compatible
with potable water.
• A properly installed flow control valve is required to
prevent thermosiphoning. Thermosiphoning is the
result of a continuous flow of water through the air
handler circuit during the off cycle. Weeping (blow off)