Sta-Rite Heater Diagnosis

[dierking502]

I need help trouble shooting my Sta-Rite SR333HD heater.

Problem:
Heater runs for ~3min, gas shuts off blower stays on, system reignites, runs for 15sec, gas shuts off, repeats run/shutoff cycle 5-6 times then system shuts down and service heater LED comes on. During this time hot water is being circulated and pushed into pool.

No sensor codes are shown on display.
No sensor LED lights on circuit board illuminate. At the end of the cycle, the Ignition box LED blinks 3 times indicating ignition lockout. If I power off system at breaker and restart it will run through this same cycle again.

Below are the Items I’ve checked / replaced by adding one new item at a time.
-New SFS sensor - no change but needed replacement
-New circuit board - no change
-New membrane - no change
-New AFS - no change
-New thermistor - no change
-New HLS - no change
-New thermal regulator - no change
-Manifold bypass valve is intact and operable
-Flow sensor is functioning

I Have not replaced AGS but LED on the circuit board is not lit up.

What am I missing here???

 

[ajw22]

Welcome to TFP.

What filter do you have? What is your filter PSI? When was the last time you cleaned your filter?

The problem you describe can be caused by low water flow. That can be due to a dirty filter or a bypass valve misset.

What model pump do you have? Is it VS? What RPM do you run it at?

Have you checked or replaced the thermal; regulator?

You can also have a flame sensing problem. Read Heater Flame Sensing - Further Reading

 

[dierking502]

AJW22, thanks for the reply. We’ve got a sand filter and have back washed recently. Changed out sand last year. Our pump is single speed, seem to have good flow. I did take apart the manifold and reassembled, the bypass valve and all seems well with it.
I did install a new thermal regulator, no change. The flame sensing issue sounds like a real possibility. Thanks

 

[dierking502]

Writing back to provide an update. Unfortunately I’m still experiencing the same run / shutoff sequence. Below are the new things I’ve tried but still getting the same result. I really thought flame sensing was my issue so most everything below is related to flame sensing rectification efforts.

I’m really at a loss on what to try next.

-Cleaned grounding surfaces within controller box
-Installed ground wire from valve side blower nut to controller box ground
-installed a new Fenwal controller
-installed a new igniter even though I put a new one in last year.
-tried a temporary supply circuit from the sub panel
-ran completely new supply circuit

I have not done any testing with a voltmeter, that’s not my comfort zone but willing to try if someone has good instructions.

I’m about 20hrs in on troubleshooting this. I still feel like it’s something simple but I’m out of ideas at this point of things to try. The controller is killing the gas supply. Is there something with the gas valve I need to test?

 

[1poolman1]

Have you examined the tubing going to the blower and air-flow switch? Even a tiny hole (mouse?) can cause the issue you're having. Have only seen it once.
Another strange cause that I've only seen on a 333. Open the heater, have it fire with a finger or two blocking the inlet screen on the blower, don't block the whole opening. Leave your hand in place, nothing to hurt you there. Heater may remain on. Found that by accident the first time. About a year later, tried it as a last resort and it was the issue again. Both heaters were 333.

 

[ajw22]

@swamprat69 may have ideas

 

[dierking502]

Have you examined the tubing going to the blower and air-flow switch? Even a tiny hole (mouse?) can cause the issue you're having. Have only seen it once.
Another strange cause that I've only seen on a 333. Open the heater, have it fire with a finger or two blocking the inlet screen on the blower, don't block the whole opening. Leave your hand in place, nothing to hurt you there. Heater may remain on. Found that by accident the first time. About a year later, tried it as a last resort and it was the issue again. Both heaters were 333.

I replaced all tubing going to and from the air flow switch. I stuck a small Allen wrens down through The barb that sits next to the gas inlet pipe hoping that might free up a clog if there was one there. Unfortunately same start up / run / shut down cycle. Put a small piece of tape over the blower inlet to mimic the fingers in front you suggested, unfortunately that didn’t work either.

Just cannot think through the logic of why it runs just fine for 3-4min and then cycles the gas off. What signal is the system not getting to tell it all is well?

 

[swamprat69]

If the heater runs for 3 min and then drops out, your problem is probably not related to the blower or air flow switch, but you would be able to confirm that by using a multimeter. You need to isolate the reason that the flame is dropping out (probably a safety). This should be the manual for your heater https://www.questargas.com/ForEmplo...ning/Boilers/Pentair_STA-RITE_MAX-E-THERM.pdf . The ladder diagram is on page 31. You would be checking the 24 volt circuit in the lower half of the diagram ( basically the Fenwal ignition module ) in order to isolate the reason for the dropout.