47
CAUTION!!!
Water with a
hardness of less than 5 grains
per gallon will usually have a
pH which can be aggressive
and corrosive causing damage
to the heat exchanger and/or
heater piping.
CAUTION!!!
Size your water
system in a way to respect
the minimum water velocity in
function of the water hardness
to prevent scaling inside the
heat exchanger:
a) If the water is 5 to 8 grain per
gallon, this is SOFT water and
you have to size the system
for a 4 ft/sec minimum water
velocity (see Figure 8-4 for
corresponding water fl ow);
8.4 - Water
chemistry
The water heater pressure drops (see
Figure 7-3) are based on potable
water with a hardness of 5 to 25
grains per gallon and a total dissolved
solids (TDS) not exceeding 350
ppm. Consult the manufacturer when
heating potable water exceeding
these specifi cations.
Heating of high hardness and/or high
total dissolved solids water increases
the pressure drops and may require a
larger circulating pump, and a revised
temperature rise specifi cation based
on the water chemistry of the water to
be heated.
Figure 8-4 Water velocity / water fl ow graph
b) If the water is 8 to 18 grain
per gallon, this is NORMAL
water and you have to size
the system for a 4 to 8 ft/sec
minimum water velocity (see
Figure 8-4 for corresponding
water fl ow);
c) If the water is 18 to 23 grain per
gallon, this is HARD water and
you have to size the system
for a 8 ft/sec minimum water
velocity (see Figure 8-4 for
corresponding water fl ow);
SOFT WATER
Less than 8 gr/
gal (137 ppm)
NORMAL WATER
8 to 18 gr/gal
(137 to 308 ppm)
HARD WATER 18 gr/
gal (308 ppm) up to
23 gr/gal (394 ppm)
8 - INSTALLATION - IW water connections
199 399 - 500 750 1000
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