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When local codes permit the use of less than four feet
high temperature piping or two elbows, provisions
should be made to always shut the heater off a minimum
of 15 minutes prior to pump shut down in order to carry
away residual heat and prevent damage to the low
temperature piping. A fireman switch included in the
time clock may be used for this purpose with instruc-
tions not to override this sequence manually. See
wiring diagram section for electrical hookup location of
the fireman switch in the electrical circuit.
NOTE (Models 926-1223): If piping is used into the
heater, this piping (copper) must be anchored or screwed
into the flange (metal) if operating pressures above 30
PSI are encountered.
CONTROLS
WATER PRESSURE SWITCH
A water pressure switch is provided in the heater to
shut down the gas valves in the event the water supply to
the heater is interrupted. It is very important to verify that
the switch electrically opens and shuts off the gas valve
when water flow to the heater is interrupted. Otherwise,
rapid and severe damage to the heater will likely occur.
(The water pressure switch should be checked and
adjusted for proper operation by a qualified service person
at the time of installation and periodically checked
thereafter. Refer to pressure switch servicing instruc-
tions in Section 4 of this manual).
WARNING: Operation of the heater without water
circulation will cause rapid and severe damage to the
heater.
AUTOMATIC CHLORINATORS AND CHEMICAL
FEEDERS
All chemicals must be introduced and completely
diluted 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 (eg,
overnight).
Chlorinators must feed downstream of the heater and
have an anti-siphoning device to prevent chemical
backup into the heater when the pump is shut off.
NOTE: High chemical concentrates from feeders and
chlorinators that are out of adjustment will cause very
rapid corrosion to the heat exchanger in the heater.
Such damage is not covered under the warranty.
8
UNITHERM GOVERNOR OPERATION
The patented Unitherm Governor is a thermostatic
mixing valve specifically designed to maintain constant
heater internal temperature between 105° to 115°F
despite continually changing flow rates from the filter
and changing pool temperatures. This narrow range is
needed to prevent damaging condensation on the burn-
ers which will occur if the heater runs for any length of
time below 100°F. It is also needed to inhibit scale
formation in the tubes by maintaining temperatures well
below accelerated scaling temperatures.
The Unitherm Governor is built into the inlet/outlet
header on models 926 through 1223. The larger sizes,
models 1287 through 4001, have an externally mounted
bypass pump that is designed to maintain the water
entering the heater at the proper temperature that will
prevent condensation and scale. Thermometers are
provided on the inlet and outlet to the heater.
COMPANION FLANGE CONNECTIONS
(Models 926-1223)
DO NOT use petroleum base assembly fluids (such
as Petroleum Jelly or Lubricating Oil). If assembly lube
is required use a silicone base such as Armoral etc.
The inlet/outlet header flange accepts a 2" copper
tube as a slip connection directly into the header. The
flange is also threaded for a 2" NPT copper male adapter.
MODELS 926 - 1223
INLET/OUTLET HEADER
FLANGE GASKET
OUTLET
INLET
HEADER FLANGE
Fig. #8221.0