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4.B.2 Hot Water Supply Piping —Water
Heater
Follow the tank manufacturer’s guidelines for
completion of the hot water system connections.
NOTE: A listed temperature and pressure relief
valve listed as complying with the Standard
for Relief Valves and Automatic Gas Shutoff
Devices for Hot Water Supply Systems (ANSI
Z21.22/CSA 4.4), of suitable discharge capacity
must be installed in the separate storage tank
system.
If this water heater is installed in a closed
water supply system, such as one having a backflow
preventer in the cold water supply line, the relief valve
may discharge periodically, due to thermal expansion.
Means (such as a properly-sized expansion tank) shall
be provided to control thermal expansion. Contact the
water supplier or local plumbing inspector on how to
control this situation.
4.B.3 Water Flow Requirements —
Water Heater
In a water heating application (an open system),
new water is constantly being introduced. With the
new water comes a fresh supply of minerals that can
be deposited on the unit’s heat exchanger. This is
commonly known as scaling. The amount of minerals
will depend upon the hardness of the water. Water can
also be aggressive, and can erode metals, including
copper, if the water is moved too quickly. The water
flow requirements for the water heater are based upon
the hardness of the water. The water flow is kept high
enough to prevent scaling, but low enough to prevent
tube erosion. For extremely soft or hard water, cupro-
nickel tubes are available. Contact a manufacturer's
representative if you have questions or concerns about
water quality.
Pump-mounted water heaters can be ordered with
standard pumps for soft or normal water. The pumps
used are sized for the head loss through the heater, plus
30 feet (9.1m) of full-sized piping (same size as heater
outlet) and a normal number of fittings. For hard water
conditions (more than 17 grains per gallon), use a
non-pump-mounted heater with a properly-sized field-
installed pump.
Table 9
specifies water flow rates for water
heaters, which will enable the user to size a pump. The
head loss shown is for the heater only, and the user
will need to add the head loss of the piping system to
properly size the pump.
4.B.4 Combined Water Heating (potable) and
Space Heating — Water Heater
NOTE:
These systems are not allowed in the
Commonwealth of Massachusetts.
Piping and components connected to this water
heater for the space heating application shall be
suitable for use with potable water.
Toxic chemicals, such as used for boiler
treatment, shall not be introduced into the potable
water used for space heating.
This water heater when used to supply potable
water shall not be connected to any heating system
or component(s) previously used with a non-potable
water heating appliance.
When the system requires water for heating at
temperatures higher than required for other uses,
an anti-scald mixing or tempering valve shall be
installed to temper the water for those uses in order
to reduce scald hazard potential.
4.B.5 Freeze Protection — Water Heater
Although these water heaters are design-
certified for outdoor installations, such installations
are not recommended in areas subject to freezing
temperatures, unless proper precautions are taken
*
.
Power outage, interruption of gas supply, failure of
system components, activation of safety devices, etc.,
may prevent a heater from firing.
Any time a heater
is subjected to freezing conditions, and the heater
is not able to fire, and/or the water is not able to
circulate, there is a risk of freezing in the heater
or in the pipes in the system.
When water freezes,
it expands. This can result in bursting of pipes in the
system, or damage to the heater, which could result in
leaking or flooding conditions.
Contact the local manufacturer's representative
for additional information.
*
Outdoor installation of volume water heaters is not
permitted in Canada.
LAARS Heating Systems