9
P/N S794 Rev. H 8-11-14
MAX-E-THERM
®
Pool and Spa Heater Installation and User’s Guide
Section 2.
Installation
Installation Instructions
Gas
Air
Mixer
Blower
Inlet
(Cold
Water)
Exhaust
Heating Coils
Outlet
(Mixed
Water)
Burner
Figure 1.
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 2" 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” (
page 32
) 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.
