Sta Rite 333K Pool Heater keeps cycling, tried everything.

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royals1969

Member
Jun 25, 2024
17
oceanside ny
I have a sta rite 333K GAS pool heater I have had for 10+ years and for the most part been pretty good to me.
Replaced sensors over the years as needed, but never had this issue.
Pool season started for me middle of May and heater has functioned normal until last week.
Now heater will not stay in heat mode, as it runs for about 2 minutes, then shuts off and will cycle back on continuously.
There are NOT any sensors complaining according to the LEDs on bottom of control board, no blinking lights on the ICM.
I have done the following to try and fix problem, but nothing has solved my issue.
Pulled out the Thermal Regulator ran heater and same problem (I tested it 130 degree water and it opened fine).
I pulled and replaced the bypass manual valve inside manifold and heater still cycles. (old bypass was still good LOL)
I jumped and shorted the Stack Flue sensor, the Automatic Gas shutoff, the High limit sensor, The Air flow switch, and Water pressure switch, all with same results.
Next I ordered a new Ignition Control module from Pentair website, same results.
Any ideas after all i have tried would be helpful.
Royals
 
royals1969 said:
I have a sta rite 333K GAS pool heater I have had for 10+ years and for the most part been pretty good to me.
Replaced sensors over the years as needed, but never had this issue.
Pool season started for me middle of May and heater has functioned normal until last week.
Now heater will not stay in heat mode, as it runs for about 2 minutes, then shuts off and will cycle back on continuously.
There are NOT any sensors complaining according to the LEDs on bottom of control board, no blinking lights on the ICM.
I have done the following to try and fix problem, but nothing has solved my issue.
Pulled out the Thermal Regulator ran heater and same problem (I tested it 130 degree water and it opened fine).
I pulled and replaced the bypass manual valve inside manifold and heater still cycles. (old bypass was still good LOL)
I jumped and shorted the Stack Flue sensor, the Automatic Gas shutoff, the High limit sensor, The Air flow switch, and Water pressure switch, all with same results.
Next I ordered a new Ignition Control module from Pentair website, same results.
Any ideas after all i have tried would be helpful.
Royals
Click to expand...
Sounds like it is not recognizing that there is flame in the combustion chamber. Get a long piece of green 12g solid wire and follow the instruction in the attached manual. It usually solves the issue. Or get Pentair's kit, 475214Z ($20.00 for a piece of wire and the instructions.
 

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royals1969 said:
At this point ill try most anything, I'll report back in a bit...
BTW is this procedure designed to ground the blower or the Flame holder?
Royals
Click to expand...
Flame sensor through the flame holder I believe, though the other items will be grounded as well, but don't need it. The flame sensor uses an extremely small current that has to flow to ground. While the blower is grounded through the metal of the combustion chamber and the wiring, the ground isn't actually used unless there is a problem. The flame-sense current starts to be sent with the ignition sequence and must be able to be "seen" once the heater fires. It is usually about 10 micro amps (10/1,000,000A) and any corrosion can stop it from flowing.
 
royals1969 said:
Can you tell me where the 'Flame Sensor' is in the chamber ? I'm thinking my heater does NOT have a flame sensor.
BTW i just tried the ground wire test and same result....cycle cycle..
Click to expand...
The ignitor is also the flame sensor. A separate current is sent down the wiring to it. When the board or Fenwal device senses that the current is flowing it will allow the heater to continue firing.
The ground wire is the first and least expensive test, but not always definitive, as you found out.
It is possible that you have a gas-supply issue after 10+ years.
If the heater has been used regularly for 10 years plus, it may be end-of-life. The flame holder can also be burned away causing this issue. Its hard to say without actually seeing it (that takes a complete teardown) and from 3000 miles. You might be able to see something in the chamber by removing the blower.
When you say it "won't stay in heat mode," is it actually changing the reading on the display? If so it is probably the circuit board.
 
I greatly appreciate all your help Poolman...
When I say it wont stay in heat mode, what i mean is the following.
Heater goes thru its normal startup procedure, and it does ignite and begin heating, and heating light is steady on.... It last for roughly 2 minutes and then you hear a 'click', and gas goes off and heating light begins to blink. Heater again goes thru its normal startup procedure and again will ignite. this is continous.
I have monitored temp on stack flow and it never gets about 350.
I am going to pull apart the combustion chamber tomorrow and see the status of the flame holder and flame holder insert.
BTW the igniter is new was replaced 3 days ago.....
Royals
 
royals1969 said:
I greatly appreciate all your help Poolman...
When I say it wont stay in heat mode, what i mean is the following.
Heater goes thru its normal startup procedure, and it does ignite and begin heating, and heating light is steady on.... It last for roughly 2 minutes and then you hear a 'click', and gas goes off and heating light begins to blink. Heater again goes thru its normal startup procedure and again will ignite. this is continous.
I have monitored temp on stack flow and it never gets about 350.
I am going to pull apart the combustion chamber tomorrow and see the status of the flame holder and flame holder insert.
BTW the igniter is new was replaced 3 days ago.....
Royals
Click to expand...
All the symptoms of not recognizing flame. But, pools are weird. It could be the board. It could be the Fenwal device. In the gray box, remove and replace all the various wires and plugs. I have had heaters start working when that is all I did. They are electronically controlled and a little corrosion on a terminal or plug can sometimes cause these kinds of issues.
 
1poolman1 said:
All the symptoms of not recognizing flame. But, pools are weird. It could be the board. It could be the Fenwal device. In the gray box, remove and replace all the various wires and plugs. I have had heaters start working when that is all I did. They are electronically controlled and a little corrosion on a terminal or plug can sometimes cause these kinds of issues.
Click to expand...
Last week I did purchase a NEW Fenwal from pentair website, and it performed the same so I returned it....
I am running out of options, maybe it could be the main control board? Anyway to test or disprove control board being the cause ?
Royals
 
royals1969 said:
Last week I did purchase a NEW Fenwal from pentair website, and it performed the same so I returned it....
I am running out of options, maybe it could be the main control board? Anyway to test or disprove control board being the cause ?
Royals
Click to expand...
Not without a different board. That's how I check, with a known good board (used from a damaged heater).
 

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1poolman1 said:
The ignitor is also the flame sensor. A separate current is sent down the wiring to it. When the board or Fenwal device senses that the current is flowing it will allow the heater to continue firing.
The ground wire is the first and least expensive test, but not always definitive, as you found out.
It is possible that you have a gas-supply issue after 10+ years.
If the heater has been used regularly for 10 years plus, it may be end-of-life. The flame holder can also be burned away causing this issue. Its hard to say without actually seeing it (that takes a complete teardown) and from 3000 miles. You might be able to see something in the chamber by removing the blower.
When you say it "won't stay in heat mode," is it actually changing the reading on the display? If so it is probably the circuit board.
Click to expand...
I just re-read this reply, so the Ignitor is also acting as a 'flame sensor' after igniting. So how can I test the igniters 'seperate current' to see if the ICM is actually sending it and/or receiving what it needs from the igniter to keep flame going ?
Royals
 
royals1969 said:
I just re-read this reply, so the Ignitor is also acting as a 'flame sensor' after igniting. So how can I test the igniters 'seperate current' to see if the ICM is actually sending it and/or receiving what it needs from the igniter to keep flame going ?
Royals
Click to expand...

Heater Flame Sensing - Further Reading

www.troublefreepool.com www.troublefreepool.com

The Fenwal has two test points for flame current FC+ and FC-. Flame current is the current that passes through the flame from sensor to ground.

The best way to measure the flame sense current is with a true RMS meter. Measure the current with a good true rms meter that can measure dc current in the microamp range.

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.

If you don't have a RMS meter you can just test for voltage between FC+ and FC- terminals to confirm if you have flame sense. Each micro-amp of flame current produces 1.0 VDC. For example, 2.6 VDC equates to 2.6 µA. Voltage is an indirect indication but easier to do with typical DIY equipment. But it's still very difficult to measure unless you make up some pin wires to clip your voltmeter to. Or you can order some insulated micro clips for the test.

The reading should be 3-8 volts and this corresponds to the millionth's of an amp signal your flame sense signal should reading. If you try to check this be very careful since you can easily short the 24 vac circuit which can blow the transformer before the 2 amp fuse blows.

When not operating, the flame current should read 0 volts dc and 0 microamps dc. DC amps and voltage should be zero when there is no flame.
 
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ajw22 said:

Heater Flame Sensing - Further Reading

www.troublefreepool.com www.troublefreepool.com

The Fenwal has two test points for flame current FC+ and FC-. Flame current is the current that passes through the flame from sensor to ground.

The best way to measure the flame sense current is with a true RMS meter. Measure the current with a good true rms meter that can measure dc current in the microamp range.

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.

If you don't have a RMS meter you can just test for voltage between FC+ and FC- terminals to confirm if you have flame sense. Each micro-amp of flame current produces 1.0 VDC. For example, 2.6 VDC equates to 2.6 µA. Voltage is an indirect indication but easier to do with typical DIY equipment. But it's still very difficult to measure unless you make up some pin wires to clip your voltmeter to. Or you can order some insulated micro clips for the test.

The reading should be 3-8 volts and this corresponds to the millionth's of an amp signal your flame sense signal should reading. If you try to check this be very careful since you can easily short the 24 vac circuit which can blow the transformer before the 2 amp fuse blows.

When not operating, the flame current should read 0 volts dc and 0 microamps dc. DC amps and voltage should be zero when there is no flame.
Click to expand...
Poolman, you are impressive with your knowledge for sure, I'll check out FC+ and FC- tomorrow, I do have two meters, a clamp style meter and a non clamp style, not sure if either can detect DC current in the micoamp range, how would i know ? Else I guess i can do the voltage test.
 
royals1969 said:
Poolman, you are impressive with your knowledge for sure,
Click to expand...

Not Poolman but your welcome.


royals1969 said:
I'll check out FC+ and FC- tomorrow, I do have two meters, a clamp style meter and a non clamp style, not sure if either can detect DC current in the micoamp range, how would i know ? Else I guess i can do the voltage test.
Click to expand...

You need to check the specs on the meters you have...

What is true-RMS? | Fluke

The need for true-RMS meters has grown as the possibility of non-sinusoidal waves in circuits has greatly increased in recent years. Some examples include variable speed motor drives, electronic ballasts, computers, HVAC, and solid-state environments.
www.fluke.com www.fluke.com
 
ajw22 said:
Not Poolman but your welcome.




You need to check the specs on the meters you have...

What is true-RMS? | Fluke

The need for true-RMS meters has grown as the possibility of non-sinusoidal waves in circuits has greatly increased in recent years. Some examples include variable speed motor drives, electronic ballasts, computers, HVAC, and solid-state environments.
www.fluke.com www.fluke.com
Click to expand...
My apologies ajw22, I did not realize you were the reply for the FC+ FC- .............
Excellent info in that reply, i plan on checking today and I'll report back results.
Royals
 
ajw22 said:
Not Poolman but your welcome.




You need to check the specs on the meters you have...

What is true-RMS? | Fluke

The need for true-RMS meters has grown as the possibility of non-sinusoidal waves in circuits has greatly increased in recent years. Some examples include variable speed motor drives, electronic ballasts, computers, HVAC, and solid-state environments.
www.fluke.com www.fluke.com
Click to expand...
AJW22: Meters specs I have, neither meter can measure DC current.
Can do AC or DC voltage, and AC current, but not DC current.
So DC voltage is best option for me correct ?
Royals
 
royals1969 said:
AJW22: Meters specs I have, neither meter can measure DC current.
Can do AC or DC voltage, and AC current, but not DC current.
So DC voltage is best option for me correct ?
Royals
Click to expand...
Try it and see what readings you get.

Be careful with your probes and don’t blow the 24V transformer.
 
So after taking the combustion chamber apart, I have 2 holes in the flame holder about the size of 1/4 inch up near the top.
So I am going to plug both holes with a nut and bolt, reassemble and see if problem goes away.
If this fixes my cycling issue, i will go ahead and order a new flame holder, but first to prove this is my problem.
Stayed tuned
Royals
 

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