MasterTemp Pool and Spa Heater P/N 474131 Rev. M 8/2020
10
Section 1. Installation
Installation
Gas
Air
Mixer
Blower
Inlet
(Cold
Water)
Exhaust
Heating Coils
Outlet
(Mixed
Water)
Burner
Figure 1.
THIS PRODUCT MUST BE INSTALLED AND SERVICED BY A PROFESSIONAL SERVICE TECHNICIAN, QUALIFIED IN POOL
HEATER INSTALLATION.
Pentair strongly recommends that all vents, pipes and exhaust systems be initially and periodically tested for proper operation. This
testing can be accomplished by using a hand-held carbon monoxide meter and/or by consulting with a gas professional.
Pool heaters must be used in conjunction with carbon monoxide detectors installed near the pool heater. The carbon monoxide
detectors must be periodically inspected for proper operation so as to insure continued safety. Broken or malfunctioning carbon
monoxide detectors must be replaced immediately.
HEATER DESCRIPTION
Figure 1 is a diagram of the heater showing how it operates. Precisely
matched orice plates meter the air and gas into the mixer. The blower
draws the air and gas through the mixer and forces it into the burner’s
ame holder. A sealed heat exchanger surrounds the ame holder,
discharging exhaust gases out the ue. 50 mm PVC water piping
connects directly to the manifold/header on the heat exchanger using
50 mm PVC slip unions provided with the heater. The outer manifold
remains cool; no heat sinks are required. A thermal regulator and an
internal bypass regulate the water ow through the heat exchanger to
maintain the correct outlet temperature. The heater operator control
panel board assembly is located on top of the heater.
SEQUENCE OF OPERATION
An electronic temperature sensing thermistor in the manifold adapter
inlet controls the heater operation. When the inlet water temperature drops below the temperature set on the operating
control, the burner controller supplies power to the combustion air blower through a series of safety interlocks. The
interlocks consist of:
• the pressure switch (PS), which senses that the pump is running,
• the high limit switch (HLS), which opens if the heat exchanger outlet temperature goes above 55° C (131° F), and
• the air ow switch (AFS), which senses the pressure drop across the air metering orice,
• the automatic gas shut-off (AGS) switch, which opens if the heat exchanger outlet temperature goes above 60° C
(140° F).
• the inlet temperature control switch, which opens if the inlet temperature goes above 45° C (110° F).
• the stack ue sensor (SFS), which shuts down the heater if the ue gas temperature reaches 249° C (480° F).
The air ow switch (AFS) senses the pressure drop across the air metering orice. As soon as there is sufcient air ow,
the AFS closes, closing the circuit to the hot surface igniter (HSI), which ignites the fuel mixture. On a call for heat,
the blower and HSI are energized. In about 20 seconds, the gas valve opens and ignition occurs. The HSI then switches
to a sensing mode and monitors the ame. The heater is equipped with a digital operating control that enables the user to
pre-set the desired pool and spa water temperatures. The control enables the user to select between pool and spa heating,
and features a digital display that indicates the water temperature.
PUTTING THE HEATER INTO SERVICE
If the heater is installed below the level of the pool, or more than 0.6 meters (2 feet) above pool level, the pressure switch
setting should be adjusted. See “WATER PRESSURE SWITCH” in the “SAFETY CONTROLS Section” (page 42) and
the “CAUTION” under “BELOW POOL INSTALLATION Section” (page 13). Before putting the heater into service
for the rst time, follow the instructions under “BEFORE START-UP” (page 40) in the front of this manual. Check for
proper operation of the heater by following the steps under “OPERATION INSTRUCTIONS.” Damage to equipment
caused by improper installation or repair will void the warranty.
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