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Pentair Pool Products MiniMax 250 Operating & Installation Manual: Maintenance; Maintenance Instructions; Pressure Relief Valve

Low nox series pool & spa heaters.
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It is recommended that you check the following items at
least every six months and at the beginning of every
swimming season.
1. Examine the venting system. Make sure there are no
obstructions in the flow of combustion and ventila-
tion air.
2. Visually inspect the main burner and the hot surface
ignitor. The normal color of the flame is blue. When
flame appears yellow, burners should be inspected
and cleaned. Check ignitor for damage.
3. Keep the heater area clear and free from
combustibles and flammable liquids.
Figure 22.
1. If possible, keep pool or spa covered when not in
use. This will not only cut heating costs, but also
keep dirt and debris from settling in the pool and
conserve chemicals.
2. Reduce the pool thermostat setting to 78° F. or
lower. This is accepted as being the most healthy
temperature for swimming by the American Red
3. Use an accurate thermometer.
4. When the proper maximum thermostat settings have
been determined, tighten the thermostat knob
If the pool is being used occasionally, do not turn the heater
completely off. Set the thermostat down to 65° F. This
If the pool won't be used for a month or more, turn the
heater off at the main gas valve. For areas where there is
no danger of water freezing, water should circulate
through the heater all year long, even though you are not
heating your swimming pool. The MiniMax NT Low
NOx should not be operated outdoors at temperatures
below 0° F. for propane and -20° F. for natural gas.
P/N 471593

Pressure Relief Valve

In some installations, a pressure relief valve (PVR) is
required on the
MiniMax NT Low
NOx. To install a
PRV, carefully drill
a 3/8 in. hole in
center of 3/4 in.
NPT port (on main
header) being
careful to drill
only thru wall at
bottom of 3/4 in.
Figure 23.
NPT port and no
deeper—now thread in the 3/4 NPT PRV. NOTE:
(A.S.M.E. version varies from illustration. It is of bronze
construction, and is supplied with the A.S.M.E. Section
IV, pressure relief valve pre-installed at factory.) Test the
relief valve at least once a year by lifting up lever.
5. Set time clock to start circulation system no earlier
than daybreak. The swimming pool loses less heat at
this time.
6. For pools that are only used on the weekends, it is
not necessary to leave the thermostat set at 78° F.
Lower the temperature to a range that can be
achieved easily in one day. Generally, this would be
10° F. to 15° F., if pool heater is sized properly.
7. During the winter or while on vacation, turn the
heater off.
8. Set up a regular program of preventative
maintenance for the heater each new swimming
season. Check heat exchanger, controls, burners,
operation, etc.
will keep the pool and the surrounding ground warm
enough to bring the pool up to a comfortable swimming
temperature in a shorter period of time.
Where freezing is possible, it is necessary to drain the
water from the heater. This may be done by opening the
drain valve, located at the inlet/outlet header (see Figure
23.), allowing all water to drain out of the heater. It
would be a good practice to use compressed air to blow
the water out of the heat exchanger. (See additional
notes under Important Notices in Introduction.)
Rev. C 11-1-01



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    none yet... this is required to see the manual.