LAARS Rheos RHCV - Install and Operating Manual - Manual (Page 20)

LAARS Heating Systems Page 20
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, 1). ANSI Z21.22
latest edition, or 2). CSA 4.4, of suitable discharge
capacity must be installed in the separate storage
tank system.
If the Rheos 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 Rheos 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 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 (potable) Heating
and Space Heating
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
V C I
Cover Screws
(Quantity=4)
Integration
DIP Switch
is set to
“Medium” at
the factory.
See Section
5.5.6 for
descriptions
of other
settings.
LED Indicator
(Percent of
Output)
Module
Connector
THROT
RANGE
MIN
OUTPUT
OFFSET
Reverse
Acting
Direct
Acting
Operation Mode
Jumper Positions
Figure 14. Proportional Control.
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 Rheos 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.
Note: Jumper must be in “Reverse Acting” mode, or Rheos will not operate properly.