Raypak 302B-902B - Manual (Page 19)

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A thermostatically controlled mixing valve is used to
mix the outlet water with the pool water. This mixed
water is supplied as the inlet water to the pool heater.
The proper configuration is shown in Fig. 15. The
active element of the valve adjusts the mixing ratio to
maintain the inlet water above 105°F.
MIXING VALVE
Fig. 14: Single Pool Heater Application
Automatic Chlorinators and Chemical
Feeders
All chemicals must be introduced and completely di-
luted into the pool or spa water before being circulated
through the heater. Do not place chlorine tablets or
bromine sticks in the skimmer. High chemical concen-
trations will result when the pump is not running (e.g.
overnight).
Chlorinators must feed downstream of the heater and
have an anti-siphoning device to prevent chemical
back-up into the heater when the pump is shut off.
Winterizing Your Heater
Heaters installed outdoors in freezing climate areas
should be shut down for the winter. To shut down
heater, turn off manual main gas valve and main gas
shut-off. Close isolation valves and remove water pip-
ing from the in/out header on the heater. Drain the
heater and any piping of all water that may experience
below-freezing temperatures.
Pool/Spa Water Chemistry
Water Hardness
Water hardness is mainly due to the presence of cal-
cium and magnesium salts dissolved in the water. The
concentration of these salts is expressed in mg/l, ppm
or grains per gallon, as a measure of relative hardness
of water. Grains per gallon is the common reference
measurement used in the U.S. water heater industry.
Hardness expressed as mg/L or ppm may be divided
by 17.1 to convert to grains per gallon. Water may be
classified as very soft, slightly hard, moderately hard
or hard based on its hardness number. The salts in
water will precipitate out when the water is heated and
will cause accelerated lime and scale accumulation on
a heat transfer surface.
Fig. 15: Mixing Valve Configuration
CAUTION: Combustion air must not be
contaminated by corrosive chemical fumes which
can damage the heater and void the warranty.
NOTE: High chemical concentrates from feeders
and chlorinators that are out of adjustment will cause
very rapid corrosion of the heat exchanger in the
heater. Such damage is not covered under the
warranty.
NOTE: Chemical imbalance can cause severe
damage to your heater and associated equipment.