LAARS Mighty Therm AP (Sizes 500-1825) - Installation, Operation and Maintenance Instructions - Manual (Page 9)

Mighty Therm Commercial Pool Heating Boiler Page 9
Auxiliary Time Clock Wiring:
If a time clock is used to control the fi lter pump
operation, a separate switch or relay must be used to
shut off the heater at least 15 minutes before the fi lter
pump is shut off. Wire the switch or relay (often called
the Fireman Switch) to the terminals shown in the wiring
diagram as “Field Interlock.”
4. All fi eld installed electrical safety devices and all
fi eld installed controllers (valve end switches, draft
switches, relays, timers) can be connected to the
heater control to the terminals shown in the wiring
diagram designated “Field Interlock.”
5. Field location of the temperature sensor is
described in Section 2.8.
Where the heater is installed with a draft fan refer to
the fan manufacturer's wiring diagram. The draft switch
should be wired across the fi eld interlock terminals in the
heater control panel.
2.6 General Piping Instructions
In addition to the bypass valve “A” and outlet valve
“B” shown in Figure 10, an inlet valve “C” should be
provided so that the heater can be readily isolated for
service. Butterfl y and globe valves are recommended for
this application to allow for precise adjustment of water
fl ows. For spa applications see Section 3.9.
Since heater outlet temperatures can reach 150°F (66°C)
in some cases, copper or CPVC are recommended
materials for heater connection piping. PVC material may
be used for the inlet valve and the piping upstream of it.
When pipe, fi ttings, grids or any other element of the
fi lter system are made of plastic materials, they may be
damaged by the momentary "back siphoning" of hot
water from the heater when the fi lter pump stops running.
The pressure relief valve installed in the tapped opening
provided in the outlet header (see Figure 9), must be
piped, but not connected, to a drain or fl oor sink. The
drain pipe must be the same size as the valve outlet and
must pitch downward from the valve. Where no special
setting of the relief valve is ordered, the factory will
furnish a 75 psi setting.
Figure 9 - Pressure Relief Valve Location
The pressure relief valve lever must be tripped at least
once a year to ensure that waterways are clean. When
manually operating lever, water will discharge through
the drain line. Precautions must be taken to avoid contact
with hot water and water damage.
2.7 Heater By-Pass Piping
All AP series heaters, 500-1825 models, must be installed
with bypass piping. Please use Figure 10 as your guide to
plumb the bypass. For spas see Section 3.9.
All models are supplied with integral pumps. These
pumps are sized for the pressure drop through the heat
exchanger, 30' of piping, and through the bypass piping
as shown in Figure 10.
If the distance from the pool heater to the pool loop
piping is greater than 15' please contact the Service
Department for assistance (see back page for phone and
fax numbers).
Any deviations from the arrangement shown may reduce
fl ow, hinder performance, and will void the warranty.
2½ inch NPT piping is shown, however, models 500I-
1430I and models 500E-1010E may be installed using 2
inch NPT piping.
All models must be installed in the primary/secondary
arrangement shown. The heater loop piping must tee into the
fi lter loop piping with the inlet and outlet connection spaced
a maximum of 4 pipe diameters apart (see Figure 10).
The integral pump will provide the right amount of fl ow
for the pool heater, and the return water to the pool will
be maintained below 104°F, provided the piping diagram
is followed correctly and the fi lter pump fl ow rate is at
least the “Minimum Filter Pump Flow Rate” in Table 4.
The outlet valve “B” and the bypass valve “A” must have
a provision for locking the handles in place (or removing
them) after the temperature rise and inlet temperature
adjustments have been made.
Heater Model Minimum Filter Pump Flow Rate
500-850 90 GPM
1010-1200 110 GPM
1430 140 GPM
1670-1825 180 GPM
Table 4 - Minimum Flow to Supply Heater Loop
2.8 Temperature Sensor Placement
and
Installation
Two temperature sensing devices are installed on the
heater that require sensing bulbs be fi eld installed
according to Figure 10.
1. Install the thermistor based sensor's immersion
well on the underside of the pool loop piping. The
well should be installed just upstream of the heater
inlet tee. DO NOT INSTALL the bulb in the
heater loop piping or down stream of the heater
outlet tee.