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1C.
Flow Requirements
For proper operation, all low volume hot water
heaters must have continuous flow through the heat
exchanger when firing. The system pump must be
capable of developing sufficient pressure to overcome
the resistance of the heater plus the entire circulating
system at the designed flow rate.
1D.
Water Chemistry
Natco equipment is designed for use in a wide
variety of water conditions. The water velocity
maintained in the heat exchanger tubes is kept high
enough to prevent scaling from hard water and low
enough to avoid corrosion from soft water. Ninety-five
percent of the urban areas in the country have water
that is compatible with this equipment, but in some
areas a water supply will contain a large quantity of
scaling chemicals or the water may be extremely soft
and corrosive. In rare situations the water will contain
both scaling chemicals and corrosive chemicals such
as calcium or sodium chloride. These conditions may
be the result of a nearby well or pumping station and
the particular condition may not be characteristic of
the entire city water system.
If an installer observes damage from these
conditions to any water handling equipment in the
area, a factory representative should be contacted
immediately for assistance in minimizing maintenance
costs. If erosion is present, the pump impeller can be
replaced to reduce water velocity. If scaling
conditions are bad, tube cleaning maintenance
schedules can be established to prevent tube burn-
out and cracking. Neglecting the problem could mean
serious damage to the heater and water system.
Scaling can be recognized as a layer deposited
on the inner walls of the tube which reduces the inner
diameter of the tube. Scale can be any color or
texture; smooth or rough, granular or amorphous.
Signs of erosion are generally pitting, cavitation,
ridges and "islands" on the inner walls of the tubes.
Since this condition results from extremely soft water
sources, or as a result of a water softening program,
the internal copper surfaces will be extremely shiny.
Other chemicals, such as chlorine or chlorides in the
water, will cause dark surfaces of erosion.
In areas where the water supply is extremely
corrosive, it is advisable to order the heater with
cupro-nickel tubes in the exchanger.
Damage From Scaling, Corrosion, or Erosion is
Not Covered by the Warranty.
Section 2
Installation
2A.
Heater Placement
The heater must be placed to provide specific
clearances on all sides for maintenance and
inspection. There must also be minimum distances
maintained from combustible surfaces. These
clearances also apply to non-combustible materials
because the heater requires air circulation for proper
operation.
Table I. Minimum Boiler Clearances
From Combustible Surfaces
Clearance
From
Top
Water Conn Side
Opposite Side
Front
Rear
Vent Pipe*
Hot Water Pipes
*Using type B Vent (refer to Manufacturer's
Instructions)
Heater should be mounted on a level surface. An
integral combustible flooring base is provided as
standard equipment on outdoor models. Indoor
models can be installed on a combustible floor with a
special base assembly which is available from the
factory. See rating plate for part number of the base
assembly.
Do not install a heater on carpeting.
Under the National Fuel Gas Code, ANSI Z223.1,
it is permissible to place the heater on floors other
than non-combustible when the installation complies
with the American Insurance Code. Figures 2, 3, 4
and 5 show common installation on combustible
flooring.
4
Indoor
Outdoor
(Inches)
(Inches)
30
unobstruct
12
24
6
24
Alcove
unobstruct
8
24
6
--
Per Code
Per Code
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