Pentair MasterTemp 400 NG Air Flow Switch

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Turbo1Ton

Turbo1Ton

Gold Supporter
Dec 26, 2019
1,995
NE Oklahoma
Pool Size
14500
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Every Friday evening from 18:00 - 20:00 my spa runs to exercise the heater. The last 2 weeks, after running for a little over 1 hour, I get an AFS alert.

Feb 9th
Alert Active AFS error - 19:15
Alert Cleared AFS error - 19:16
Alert Active AFS error - 19:30
Alert Cleared AFS error - 19:44

Feb 16th
Alert Active AFS error - 19:20
Alert Cleared AFS error - 19:21
Alert Active AFS error - 19:55
Alert Cleared AFS error - 19:58

I have pulled the covers and looked for any blockages or anything abnormal such as rodent chews or anything like that. Everything looks ok to me. Wondering if anyone can think of any reason why it would run for so long before getting the AFS error?

Have been running it this evening. According to the notifications log in the app, I got an AFS error initially but the heater started up just fine. Also looks like in the inactive notifications, I've got a few different weak flame alarms. I'm assuming that indicates the ionization rod is starting to go out, maybe? And now that I've let it run a while, I see I also got a "Flame No Call For Heat Alarm" a couple of times.

Are the AFS's a failure prone part that I should just go ahead and replace?

Heater was installed with the pool in late 2019, early 2020. Only thing I've had to do to the heater is had to change the thermal regulator last year.

Also noticed this evening that the RS-485 control uses the internal MasterTemp thermistor for control, not the water temp thermistor wired into the Intellicenter.

--Jeff
 

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That is correct. The “Connected MasterTemp” with RS-485 control does temperature control differently and the IntelliCenter tells it the temperature to heat to and the MasterTemp temperature control is used.

Those alerts are all a new feature and we don’t know much about them yet.

When the heater gets the AFS error does the heater shutdown?
 
I probably figured out the temperature control part when I swapped the boards and connected via 485, but forgot about it. :ROFLMAO:

Is weird though because I haven't noticed the heater not heating to temp (Intellicenter displayed temp) until recently. Maybe my water temp thermistor is starting to drift.

I did not realize those alerts were new. I'll keep watching them.

Nope, heater does not shut down. I think it may be tripping the AFS and clearing relatively quickly.

--Jeff
 
The alerts were implemented with the RS-485 communication. Before that heater faults shutdown the heater and tripped LEDs on the back of the board. You had to open up the heater and turn the top upside down to see the error.

These can be nuisance alarms. Sort of like the Check Engine light on your car.

I would keep an eye on the heater but not do anything until it shows actual problems.
 
Thanks Allen. That was my game plan, but thought I'd ask about it just to see if anyone had seen/heard of it happening before.

--Jeff
 
JamesW said:
Check the stack flue temperature.
Click to expand...
I'll do that one night this week. Wait... I can't do that while connected via RS-485, can I? I don't know how to access the heater menu when the RS-485 is connected. Any button presses result in the display saying RS-485 control. It may be next weekend before I have enough time to get out and disconnect the 485 wires.

--Jeff
 
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Ok, had some extra time that I didn't think I was going to have this evening.

Disconnected the RS-485 wires so I could access the menu and get to the SFS temp. Highest I saw it get to was 301F.

I don't know if I got the AFS alert since the 485 comms were disconnected, and it has been happening at startup of the heater. I didn't see anything come across the display, but I could have missed it.

--Jeff
 
Flame Current Measurement.

Flame current is the current that passes through the flame from sensor to ground.

To measure flame current, connect a True RMS or analog DC micro-ammeter to the FC+ and FC- terminals.

Readings should be 1.0 µA DC or higher. If the meter reads negative or below "0" on scale, meter leads are reversed.

Reconnect leads with proper polarity.

Alternately, a Digital Voltmeter may be used to measure DC voltage between FC+ and FC- terminals.

Each micro-amp of flame current produces 1.0 VDC.

For example, 2.6 VDC equates to 2.6 µA.

A good burner ground that matches the control ground is critical for reliable flame sensing.

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JamesW said:
Check the flame current with the heater off and watch it as the heater comes on.
Click to expand...
Just checked it. 0 VDC at first, then once the circuit was triggered a -0.057VDC, and once ignition started, it was at 3.9 VDC and rose to about 4.5VDC after 30 seconds or so.

I just got an ignition lockout alarm notification at startup. But it started up just fine.

Also, I would think the 'Flame No Call For Heat' alarm/notification would indicate that I was seeing flame when there was none.

I'm gonna run it again this evening for a couple hours, but I'm pretty much done messing with it until something actually breaks.

--Jeff
 
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