LAARS Mighty Therm2 MT2V (Sizes 500–2000 MBTU/h) - Install and Operating Manual - Manual (Page 15)

Mighty Therm 2
Page 15
The Mighty Therm2 can be used with several
different types of readily available storage tanks. A pump
draws water from the storage tank and pumps the water
through the heater and back into the tank. Pump-mount-
ed units have a circulating pump built into the water
heater. The pumps used are sized for the headloss
through the heater, plus 30 feet (9.1m) of full-sized pip-
ing (same size as boiler outlet) and a normal number of
fittings. Pumps used on pump-mounted unit are sized for
soft/normal or hard water, so make sure a pump-mounted
unit matches the water quality of the installation.
Pipe the outlet from the heater’s relief valve
such that any discharge from the relief valve will be
conducted to a suitable place for disposal when relief
occurs. Do not reduce line size or install any valves in
this line. The line must be installed to allow complete
drainage of both the valve and the line.
Suggested piping diagrams are shown in Figures 11
through 14 . These diagrams are meant only as a guide.
Components required by local codes must be properly
installed.
The minimum inlet water temperature for the
Mighty Therm2 is 120°F (49°C) to avoid condensing on
the copper coils.
4B.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 the Mighty Therm2 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.
4B.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 Mighty Therm2 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 Laars
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 or with
pumps for hard water. The pumps used are sized for the
headloss through the heater, plus 30 feet (9.1m) of full-
sized piping (same size as heater outlet) and a normal
number of fittings.
Table 9 specifies water flow rates for water heaters,
which will enable the user to size a pump. The headloss
shown is for the heater only, and the user will need to add
the headloss of the piping system to properly size the pump.
4B.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.
4B.5 Freeze Protection – Water Heater
Although Mighty Therm2 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 factory representative or Laars for
additional information.
SECTION 5.
Electrical Connections