Section 3. Installation; Heater Description; Sequence Of Operation; Putting The Heater Into Service - Pentair MASTERTEMP 125 Guía De Instalación Y Usuario

Section 3. Installation Instructions
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Section 3: Installation Instructions

HEATER DESCRIPTION

Figure 1 is a diagram of the heater showing how it operates.
Precisely matched orifice 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 flame holder. A sealed heat exchanger surrounds the flame
holder, discharging exhaust gases out the flue.
Two inch PVC water piping connects directly to the manifold/header on
the heat exchanger using 1.5" 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 flow 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 135° F (57° C), and
• the air flow switch (AFS), which senses the pressure drop across the air metering orifice,
• the automatic gas shut-off (AGS) switch, which opens if the heat exchanger outlet temperature goes above
140° F (60° C).
• the stack flue sensor (SFS), which shuts down the heater if the flue gas temperature reaches 480° F (249° C).
The air flow switch (AFS) senses the pressure drop across the air metering orifice. As soon as there is sufficient air flow,
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 flame.
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 two feet above pool level, the pressure switch setting
should be adjusted. See WATER PRESSURE SWITCH, in the SAFETY CONTROLS Section.
Before putting the heater into service for the first time, follow the instructions under "BEFORE START-UP"
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.
MASTERTEMP 125 Pool and Spa Heater Installation and User's Guide
Air
Mixer
Inlet
(Cold
Water)
Outlet
Burner
(Mixed
Water)
Blower
Heating Coils
Figure 1.
(page
32) in the
Rev. C 3/2019