Pentair MiniMax NT Standard Series - Manual (Page 26)

P/N 472032 Rev. A 1-2-02
26
NORMAL OPERATION SEQUENCE
(Refer to Figure 20 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 Standard 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 1 minute. 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 and the heater will fire. At
this time, if flame is not safely established as detected by the flame sensing circuit, 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.
3. After normal firing of the heater (main burners) the heater will continue to operate until the
temperature setpoint is reached (thermostat satisfied). As the pool/spa loses heat the heater will refire
and continue to operate cycling automatically to maintain the selected temperature setpoint for either
the pool or spa. If at anytime during the firing of the heater an unsafe condition is detected the
heater will stop firing and an automatic safe shutdown sequence will begin. Investigate and have
corrected the cause of the abnormal firing termination before placing heater back in operation.
Please Note: During the firing of the heater, you decide to change to the pool or spa selection by
depressing the selector key for “POOL” or “SPA”, the heater will first acknowledge the new selection by
flashing the new selection’s corresponding selection LED “POOL” or “SPA”, however, the heater will first
complete a safe shutdown sequence before automatically switching to the new selected setting and safely
initiating a new firing sequence using the new temperature setpoint. During this automatic crossover
sequence the keyboard on the Pentair Temperature Controller 7800 will not accept any further keying until
the cycle completes—the exception is you may still stop the heater with the “OFF” key.
Troubleshooting—Normal Operation Sequence of Heater