John Wood Envirosense Power Direct Vent (prior to May 2010) - Manual (Page 12)

12
closed water sYsteMs
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 flow preventers.
Devices such as these cause the water system to be a closed system.
therMal eXpansIon
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 build up. 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 should be installed
on all closed systems to control the harmful effects of thermal
expansion..
fIGure 10.
note: to protect against untimely corrosion of hot and cold
water fittings, it is strongly recommended that di-electric unions
or couplings be installed on this water heater when connected
to copper pipe, see figure 2 also.
cheMIcal vapor corrosIon
CORROSION OF THE FLUEWAYS AND VENT SYSTEM MAY OCCUR IF
AIR FOR COMBUSTION CONTAINS CERTAIN CHEMICAL VAPORS. SUCH
CORROSION MAY RESULT IN FAILURE AND RISK OF ASPHYXIATION.
Spray can propellants, cleaning solvents, refrigerator and air
conditioning refrigerants, swimming pool chemicals, calcium and
sodium chloride (water softener salt), waxes, and process chemicals
are typical compounds which are potentially corrosive.
Do not store products of this sort near the heater. Also, air which is
brought in contact with the heater should not contain any of these
chemicals. If necessary, uncontaminated air should be obtained from
remote or outside sources. The limited warranty is voided when failure
of water heater is due to a corrosive atmosphere. (See limited warranty
for complete terms and conditions).
water pIpInG
HOTTER WATER CAN SCALD:
Water heaters are intended to produce hot water. Water heated to a
temperature which will satisfy space heating, clothes washing, dish
washing, cleaning and other sanitizing needs can scald and permanently
injure you upon contact. Some people are more likely to be permanently
injured by hot water than others. These include the elderly, children, the
physically or developmentally disabled. If anyone using hot water fits into
one of these groups or if there is a local code or state law requiring a
certain temperature water at the hot water tap, 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, see Figure 2. Valves for reducing point of use temperature by
mixing cold and hot water are also available:
Consult a Qualified Installer or Service Agency. Follow manufacturer’s
instructions for installation of the valves. Before changing the factory
setting on the thermostat, read the “Temperature Regulation” section in
this manual.
This water heater shall not be connected to any heating systems or
component(s) used with a non-potable water heating appliance.
All piping components connected to this unit for space heating
applications shall be suitable for use with potable water.
Toxic chemicals, such as those used for boiler treatment shall not be
introduced into this system.
When the system requires water for space heating at temperatures higher
than required for domestic water purposes, a tempering valve must be
installed. Please refer to Figure 2 for suggested piping arrangement.
InstallInG the new water heater