Pentair MASTERTEMP weird burner cycling

[Munkustrap]

OK, it's into weirdness now.....

Pentair MASTERTEMP heater: When initially engaged in SPA mode, works well and heats continually until it reaches 80-90 degrees. At this point, the "heat" light begins flashing, blower stays ON, but burner cycles OFF. NO red lights on panel OR on circuit board are ON. In about 30 seconds, burner cycles ON again, amber "heat" light is steady, and the cycle repeats. Here are the other things that were checked:

1. Thermistor tests perfectly and registers correct water temperature.
2. MAX temp set at 125 degrees.
3. HLS-AGS-AFS-WFS remain in normally CLOSED position during all cycling events. (therefore NO red lights on board)
4. Thermostat function tests normal and opens at 120 degrees.
5. Water flow/pump speed/internal bypass all normal.
6. Flue gas temperature does not get above 300 degrees and indicates normally.

At this point, I wonder about flame rectification issues, possibly ignition control module or even control board, although the indications lead me to believe the board is ok.

Any thoughts about this mystery are gratefully appreciated!

 

[JJ_Tex]

Is this a new heater, or did it just start doing this? If it is new, did they install a new gas meter as well? For mine the gas company had to install a larger meter, which was free.

Also, if its new, I would be calling Pentair for a warranty claim.

 

[ajw22]

Welcome to TFP.

What type of filter do you have and what is the pressure?

That is why we ask you to Create_Your_Signature with details of your pool and equipment.

 

[bongardjm]

Same thing happened to my Mastertemp 300. No error codes, everything tested out OK, but kept cycling around 80-90 degrees. See my thread --> Mastertemp 300 - SOLVED! - Cycling -
Maybe it will help?
Ended up being a rusted tube sheet. Replaced it and now works fine.

 

[setsailsoon]

Munk,

If your heater is under warranty I'd call them. If not, and you're comfortable/working on the heater 240 vac controls you can verify flame sensing by clipping micro clips on the test pins. With a true RMS meter you should measure at least 1.3 micro amps of current. If you don't have a meter that will test for this a good volt meter should show 1-4 volts.

I'm pretty certain your problem is not flame sensing since the ignition cycle would stop by closing the gas valve about 7 seconds after flame if it does not sense flame. Much more likely you have a plugged filter that is reducing flow after the pump runs for a bit that then shuts the heater flow switch or you have a temp sensor that is reading way high (this is the way they normally fail).

I hope this helps.

Chris

 

[setsailsoon]

Same thing happened to my Mastertemp 300. No error codes, everything tested out OK, but kept cycling around 80-90 degrees. See my thread --> Mastertemp 300 - SOLVED! - Cycling -
Maybe it will help?
Ended up being a rusted tube sheet. Replaced it and now works fine.

Bong,
Just looked at your post. I went through a similar bout of heater H**L but mine was quite different. Here's the details. My guess is your tube sheet rust may have caused a transient ground issue but weird that it happened at the same temp.

Chris

 

[setsailsoon]

Munk,

If you think it might be a ground issue. You can rule it out with something i recently discovered. Details are here.

Chris