Introduction; Thermal Expansion - Rheem Marathon MR105/473185 Use & Care Manual

Thank you for buying your non-metallic electric water heater. Your new water
heater is made of the latest materials and will not rust or corrode. It will give
many years of hot water service when installed, operated and maintained
according to the instructions in this manual.
Your water heater is completely assembled and ready to install. This manual
provides the general instructions for installation. Because of several variables,
such as the installation location, existing piping, and local codes, it is impossi-
ble to provide exact instructions for everyone's specific needs. For this reason,
it is suggested that the entire manual be read prior to beginning any installation
work, then carefully plan the installation. This can help to avoid costly mistakes
including damage to the water heater, not covered under terms of the warranty.
Almost all new products (automobiles, boats, clothing, plastic and wood items,
etc.) have an odor or smell to them for a time. This water heater may also have
a "new" smell or odor to it due to the non-metallic materials used in the manu-
facturing process. This "new" smell is not harmful, and will disappear in a short
time.
The vacuum valve, which must be used when installing the water heater, is
factory installed.
The location chosen for the water heater must take into consideration the fol-
lowing:
LOCAL INSTALLATION REGULATIONS
This water heater must be installed in accordance with these instructions,
local codes, utility company requirements or, in the absence of local codes,
the latest edition of the National Electrical Code. It is available from some local
libraries or can be purchased from the National Fire Prevention Association,
Batterymarch Park, Quincy, MA 02269 as booklet ANSI/NFPA 70.
LOCATION
Locate the water heater in a clean dry area as near as practical to the area of
greatest heated water demand. Long uninsulated hot water lines can waste
energy and water. Place the water heater in such a manner that the thermostat
and element access panels can be removed to permit inspection and servicing
1. INSPECT SHIPMENT — Inspect water heater for possible damage.
Check the markings on the rating plate of the water heater to be certain the
power supply corresponds to that for which the water heater is equipped.
2. THERMAL EXPANSION — Determine if a check valve exists in the
inlet water line. It may have been installed in the cold water line as a
separate back flow preventer, or it may be part of a pressure reducing
valve, water meter or water softener. A check valve located in the cold
water inlet line can cause what is referred to as a "closed water sys-
tem". A cold water inlet line with no check valve or back flow prevention
device is referred to as an "open" water system.
As water is heated, it expands in volume and creates an increase in the
pressure within the water system. This action is referred to as "thermal
expansion". In an "open" water system, expanding water which exceeds
the capacity of the water heater flows back into the city main where the
pressure is easily dissipated.

Introduction

A — Diameter of water heater plus 2" min.
B — Maximum 2"
Figure 1. — Auxiliary Drain Pan
such as removal of elements or checking controls. The water heater and water
lines should be protected from freezing temperatures. Do not install the water
heater in outdoor, unprotected areas, or near any other appliances where high
temperature are present, such as wood burning stoves, boilers or furnaces.
High temperatures can warp or otherwise damage the non-metallic construc-
tion of this water heater.
!
CAUTION
The water heater should not be located in an area where leakage of
the tank or connections will result in damage to the area adjacent
to it or to lower floors of the structure. Where such areas cannot be
avoided, it is recommended that a suitable drain pan, adequately
drained, be installed under the water heater.
NOTE: Auxiliary drain pan installation MUST conform to local
codes.
Drain Pan Kits are available at your local retail outlet or service center.
Installation
A "closed water system", however, prevents the expanding water from
flowing back into the main supply line, and the result of "thermal expan-
sion" can create a rapid, and dangerous pressure increase in the water
heater and system piping. This rapid pressure increase can quickly reach
the safety setting of the relief valve, causing it to operate during each
heating cycle. Thermal expansion, and the resulting rapid, and repeated
expansion and contraction of components in the water heater and piping
system can cause premature failure of the relief valve, and possibly the
heater itself. Replacing the relief valve will not correct the problem!
The suggested method of controlling thermal expansion is to install an
expansion tank in the cold water line between the water heater and the
check valve. The expansion tank is designed with an air cushion built in
that compresses as the system pressure increases, thereby relieving the
over pressure condition and eliminating the repeated operation of the
relief valve. Other methods of controlling thermal expansion are also
available. Contact your installing contractor, water supplier, or plumbing
inspector for additional information regarding this subject.
2
B
A
To open drain, line should
be at least / " ID and
3
4
pitched for proper drainage.