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Pentair Pool Products MiniMax 250 Operating & Installation Manual: Trouble Shooting; Normal Operation Sequence

Low nox series pool & spa heaters.
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Troubleshooting—Normal Operation Sequence of Heater


(Refer to Figure 21 of Pentair Temperature Controller 7800 keyboard)
The heater features a fully automated firing start-up and shutdown sequence under the control of the
MiniMax NT Low NOx Pentair Temperature Controller 7800.
Now that the heater has been properly installed and wired for either remote operation or local operation, and
you have setup the Pentair Temperature Controller 7800 temperature setpoints as described earlier in manual
in Thermostat section, the following is the normal operating sequence when the heater turns on the and the
thermostat calls for heat for the pool or spa.
1. The fan will start beginning the heater's safety prepurging cycle which lasts for 2 minutes. If at anytime
during the prepurge cycle the Pentair Temperature Controller 7800 detects that a safety control is not
working due to either a safety control malfunction or other unsafe condition the firing sequence will stop
until the unsafe condition is removed— "the fault icon related to the problem will illuminate".
2. After proper completion of the prepurge cycle, the hot surface ignitor (glow coil) will turn on (preheat)
for 40 seconds. Once the 40 seconds is passed, the main gas valve will open. At this time, if flame is not
safely established and is dectected by the flame sensing curcuit, the ignition module and Pentair
Temperature Controller 7800 will shut down and will display an ignition fault and luminate the red
service light. Please note that on initial firing of heater when gas supply piping is full of air or after long
period of non-operation of the heater it is normal for the first ignition attempt to not complete. To clear
the fault condition power to the Pentair Temperature Controller 7800 must be cycled to reset system. If
heater continues to fail to light have heater inspected by a qualified service person before placing heater
back in service.
Insufficient waterflow (pump icon displays), excessive water temperature (high limit icon) cause a
"soft-lockout" of the firing sequence—which means if the cause of the problem clears by itself (or with
human intervention ie., turning on pump, etc.) such as a slow to prime water pump finally pumping
adequate waterflow causing the water pressure (safety) switch to close, the ignition sequence
automatically restarts again.
The other category of fault conditions lead to a "hard lockout" of the firing sequence which require a
qualified service person to correct before the heater is returned to service. In "hard lockout" the heater
must be manually reset (by toggling power to Pentair Temperature Controller 7800) after correction of
the fault condition.
Examples of causes of "hard lockouts" include inadequate gas supply pressure and/or failure of fan or
fan pressure switches, which all appear as air/gas pressure faults illuminating "blower fan" fault icon and
RED "service required" LED.
P/N 471593
Rev. C 11-1-01



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  • Ken Lobsinger Mar 14, 2016 02:53:
    none yet... this is required to see the manual.