I have a Sta-Rite Max-E-Therm. 333 heater and it starts fine and no codes show but the temperature going to the pool is lower than last season. My pool use to go up 3 degrees an hour now only one degree. The flow is good with 12 psi pressure. Any thoughts on the problem?
Sta Rite 333 Heater not getting hot enough
- Thread starter Rlwolfinger
- Start date
What is the pool volume?
Press and hold the Pool On button until the exhaust temperature shows on the display.
Watch the gas meter. You should use about 333 cubic feet of gas per hour or about 1,000 per 3 hours.
Press and hold the Pool On button until the exhaust temperature shows on the display.
Watch the gas meter. You should use about 333 cubic feet of gas per hour or about 1,000 per 3 hours.
The pool is 11,000 gallons. Do you think the thermostat may be open or partiall opened all the time instead of opening at 120F? I watch a YouTube video and thought maybe that is the problem the temperature is not high enough. Thoughts? I will pull the thermostat today and inspect and run a temperature test on the stove with a meat thermometer in the water but not touching the bottom of the pan.
The heater is propane. What should the exhaust temperature be?
The heater is propane. What should the exhaust temperature be?
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You should be gaining about 3 degrees per hour. (333000x.84)÷(11000x8.34) = 3 degrees per hour.
Here is what the normal exhaust temperature should be:
What temperature are you getting?
Are you watching the gas meter?
Is the pool covered?
Here is what the normal exhaust temperature should be:
- Below 250 degrees...very low
- 250 to 290 ..................low
- 290 to 350.................acceptable
- 350 to 480 ..................high
- Above 480...................error/shutdown.
What temperature are you getting?
Are you watching the gas meter?
Is the pool covered?
If you know the flow rate in gpm, you can calculate the expected temperature rise from inlet to outlet.
For example, at 40 gpm, you should see a temperature rise of about 14 degrees.
(333000x.84)÷(40x60x8.34) = 14 degrees.
What pump do you have?
Do you have automation?
You really need about 5 or more hours to really evaluate the heat gain rate.
Have you let the heater run for at least 5 hours to see if you're getting the correct amount of heat?
For example, at 40 gpm, you should see a temperature rise of about 14 degrees.
(333000x.84)÷(40x60x8.34) = 14 degrees.
What pump do you have?
Do you have automation?
You really need about 5 or more hours to really evaluate the heat gain rate.
Have you let the heater run for at least 5 hours to see if you're getting the correct amount of heat?
The unit runs on propane and has an exhaust temperature of 408F. I do not have automation. I have run the unit for over 11-12 hours continuously to get the temperature up in the pool for the grandchildren. It started at 68F and got to 80-81F. My 500 gallon propane tank has a very small percentage use gauge. It was filled to about 80% about a week ago and is now down to 60+% so I went through a lot of propane. I have an 120 volt AC pump. It is a 1hp WhisperFlo WF-24. I did not see a flow rate. Can you figure it? The water flow appears good. I run about 12-14 PSI. I took out the thermostat and it was closed tightly so water was not bypassing. It stayed closed until 120-122F as expected. I can feel the temperature of the water entering the pool and it is warm but not as hot as from last year and the past. The unit is starting the 10 season. The pool is not covered. The temperature outside was in the high 60s to low 70s. When the sun was out, I think the solar radiation help the pool to heat up a bit faster.
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408 degrees is way too hot and indicates a problem with heat transfer.
Normally, about 84% of the 333,000 btu/hr transfers to the water and the rest goes out the exhaust, which should be about 308 degrees.
Your exhaust is about 100 degrees too hot, which I estimate is about 27,000 btu/hr extra waste heat. So, that implies an efficiency of about 76% vs. 84%.
Even at 76% efficiency, the water should gain about 2.75 degrees per hour.
I would estimate the flow rate at about 70 gpm, which should give you a temperature rise of about 8 degrees from inlet to outlet at 84% efficiency.
You can put a temperature sensor on the pipe going to the heater and coming from the heater to see the temperature rise.
The high exhaust temperature might be due to a bad internal bypass or maybe a scaled heat exchanger.
Verify the internal bypass by looking in the inlet to see the spring part of the bypass and by looking in the hole where the thermal regulator goes to see the disc part.
You can push down the plunger from the inlet side and you should be able to see the disc moving in the hole where the thermal regulator goes.
The heater should be using about 3.64 gallons of propane per hour. At 11 hours, that's 40 gallons.
You seem to be getting about 1 degree per hour, which is substantially less than expected.
If the pool is uncovered, you can lose a substantial amount of heat. So, take that into consideration.
Normally, about 84% of the 333,000 btu/hr transfers to the water and the rest goes out the exhaust, which should be about 308 degrees.
Your exhaust is about 100 degrees too hot, which I estimate is about 27,000 btu/hr extra waste heat. So, that implies an efficiency of about 76% vs. 84%.
Even at 76% efficiency, the water should gain about 2.75 degrees per hour.
I would estimate the flow rate at about 70 gpm, which should give you a temperature rise of about 8 degrees from inlet to outlet at 84% efficiency.
You can put a temperature sensor on the pipe going to the heater and coming from the heater to see the temperature rise.
The high exhaust temperature might be due to a bad internal bypass or maybe a scaled heat exchanger.
Verify the internal bypass by looking in the inlet to see the spring part of the bypass and by looking in the hole where the thermal regulator goes to see the disc part.
You can push down the plunger from the inlet side and you should be able to see the disc moving in the hole where the thermal regulator goes.
The heater should be using about 3.64 gallons of propane per hour. At 11 hours, that's 40 gallons.
You seem to be getting about 1 degree per hour, which is substantially less than expected.
If the pool is uncovered, you can lose a substantial amount of heat. So, take that into consideration.
Verify the amount of propane used. You should use about 10% (50 gallons) in about 13.7 hours.
Verify the gas pressure at the gas valve inlet and outlet.
Figure out why the exhaust is too hot.
Make sure that the heater is not cycling on and off due to an error. Watch it for an hour as closely as possible.
Do you have an external bypass on the heater?
Note: Maxetherm is the same as mastertemp.
www.troublefreepool.com
Verify the gas pressure at the gas valve inlet and outlet.
Figure out why the exhaust is too hot.
Make sure that the heater is not cycling on and off due to an error. Watch it for an hour as closely as possible.
Do you have an external bypass on the heater?
Note: Maxetherm is the same as mastertemp.
Pentair MasterTemp Heaters - Further Reading
www.troublefreepool.com
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You can get a Pentair 10k water temperature sensor and put it somewhere downstream from the heater to see what the outlet temperature is.
You can use a multimeter to test the resistance of the sensor and convert it to a temperature value using a 10k thermistor chart. Ohms to temperature charts are available online and there's one in the Pentair automation manuals (Easytouch, intellitouch, Intellicenter etc.)
You can get a display that converts the ohm reading to temperature.
The inlet temperature is displayed on the heater display.
Knowing the temperature rise can help diagnose the problem.
You can use a multimeter to test the resistance of the sensor and convert it to a temperature value using a 10k thermistor chart. Ohms to temperature charts are available online and there's one in the Pentair automation manuals (Easytouch, intellitouch, Intellicenter etc.)
You can get a display that converts the ohm reading to temperature.
The inlet temperature is displayed on the heater display.
Knowing the temperature rise can help diagnose the problem.
JamesW,
I have orders an o ring kit and the manfoild bypass to have on hand when I disconnect the heater to perform your suggestions. I ran the heater for around 24 hours over four days so I burned a lot of propane for little result except happy grandkids properly socially distant. I am not going to run the temperature check right now but will service the manifold. I know the temperature is down by feeling it at the outlet into the pool but just do not know by how much. If the bypass is bad, I doubt I will pull the cover over the coil to inspect it. The heater had no problem the end of last year when I was using it so I do not think scaling would occur to that degree over a winter in Maryland. I would think scaling of the coil would be a gradual decline in performance and that was not the case. I understand the bypass failure is a common problem.
All of your heat calculations have explained the resultant performance. I think we can assume the temperature is reduced at the outlet by the heat up the stack being so high beside feeling a big difference from last year. I remember having the hot water from heater hitting my back during Fall swims and not wanting to leave the hot water inlet into the pool or being disapoointed when the heater reached temperature.
Thanks for your help so far. It will be a week or so before I get the parts and perform the work. I will advise on this site. Again thanks so far.
Rick
I have orders an o ring kit and the manfoild bypass to have on hand when I disconnect the heater to perform your suggestions. I ran the heater for around 24 hours over four days so I burned a lot of propane for little result except happy grandkids properly socially distant. I am not going to run the temperature check right now but will service the manifold. I know the temperature is down by feeling it at the outlet into the pool but just do not know by how much. If the bypass is bad, I doubt I will pull the cover over the coil to inspect it. The heater had no problem the end of last year when I was using it so I do not think scaling would occur to that degree over a winter in Maryland. I would think scaling of the coil would be a gradual decline in performance and that was not the case. I understand the bypass failure is a common problem.
All of your heat calculations have explained the resultant performance. I think we can assume the temperature is reduced at the outlet by the heat up the stack being so high beside feeling a big difference from last year. I remember having the hot water from heater hitting my back during Fall swims and not wanting to leave the hot water inlet into the pool or being disapoointed when the heater reached temperature.
Thanks for your help so far. It will be a week or so before I get the parts and perform the work. I will advise on this site. Again thanks so far.
Rick
The heat out of the stack can only account for a small difference. Instead of 3 degrees per hour, you would get 2.75 degrees per hour.
The extra heat going out of the stack can be due to scaling inside the heat exchanger or sooting outside the heat exchanger or maybe low water flow due to a bad bypass.
There's something else going on if the heater really is only adding 1 degree per hour.
That points to a weak flame, which can be caused by low gas pressure.
I would check the gas pressure to verify that it's remaining good while the heater is on.
If the pool is uncovered, you will lose a substantial amount of heat. That can account for a loss of 2 degrees per hour.
So we can't conclusively say how much the heater is underperforming.
I would get a Pentair 520272 temperature sensor and put it downstream from the heater to see what the outlet temperature is. If you don't have automation to read the sensor, you can use a good multimeter to check the resistance and convert it to temperature.
Check the amount of gas being used to see if it matches what it should be. If it's using the correct amount of gas, then it's probably providing the correct amount of heat unless there is a problem with the combustion.
Watch the heater to see if it's running continuously or if it's cycling on and off.
You can check for water in the combustion chamber by removing one of the bottom manifold bolts to see if water comes out.
The extra heat going out of the stack can be due to scaling inside the heat exchanger or sooting outside the heat exchanger or maybe low water flow due to a bad bypass.
There's something else going on if the heater really is only adding 1 degree per hour.
That points to a weak flame, which can be caused by low gas pressure.
I would check the gas pressure to verify that it's remaining good while the heater is on.
If the pool is uncovered, you will lose a substantial amount of heat. That can account for a loss of 2 degrees per hour.
So we can't conclusively say how much the heater is underperforming.
I would get a Pentair 520272 temperature sensor and put it downstream from the heater to see what the outlet temperature is. If you don't have automation to read the sensor, you can use a good multimeter to check the resistance and convert it to temperature.
Check the amount of gas being used to see if it matches what it should be. If it's using the correct amount of gas, then it's probably providing the correct amount of heat unless there is a problem with the combustion.
Watch the heater to see if it's running continuously or if it's cycling on and off.
You can check for water in the combustion chamber by removing one of the bottom manifold bolts to see if water comes out.
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JamesW, I disassembled the heater and found the problem. The coil is heavily scaled on the outside. I am going to power wash it. YouTube suggested that. It is clean inside the tubes. I am awaiting a sealing gasket to put it back together. Thanks for help. Rick
The external scaling/sooting can only account for part of the reduction in heating.
You should get about 3 degrees per hour. With scaling/sooting you should expect 2.75 degrees per hour.
If you're only getting 1 degree per hour, then you're missing 1.75 degrees per hour, which might indicate a combustion problem, which would be consistent with the sooting.
You should get about 3 degrees per hour. With scaling/sooting you should expect 2.75 degrees per hour.
If you're only getting 1 degree per hour, then you're missing 1.75 degrees per hour, which might indicate a combustion problem, which would be consistent with the sooting.
There is no evidence of sooting in the stack. The perforated burner canister is clean. I did not take the burner assemble apart to look inside? Should I do that if I see no external signs? I do not have the gasket kit for the burner assemble but do not think it is that critical. Thoughts?
My stack temperature was 409F. Is sooting typical of that high stack temperature? I would think that poor heat transfer to the coil would be the cause of the high stack temperature.
My stack temperature was 409F. Is sooting typical of that high stack temperature? I would think that poor heat transfer to the coil would be the cause of the high stack temperature.
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What is perforated?
If the combustion chamber has holes in it, you should not use the heater.
At 10 years old, the best choice is to replace the heater.
Have the gas supply evaluated by a qualified gas contractor to make sure that it's in good working condition.
If the combustion chamber has holes in it, you should not use the heater.
At 10 years old, the best choice is to replace the heater.
Have the gas supply evaluated by a qualified gas contractor to make sure that it's in good working condition.
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The flame holder is perforated to allow the heat from the flame to escape into the chamber. There are small holes in a pattern on the flame holder. The flame holder is in perfect shape and there is no sign of soot plugging any of the holes.
I am going to hopefully assemble the heater today and give it a test. I will let you know if it works.
I am going to hopefully assemble the heater today and give it a test. I will let you know if it works.
I broke the igniter. I was cautioned about that but got carried away with vacuuming and broke it off. I disassembled it and ordered a new one. I will install the heater and plumb and wire it up and when the igniter comes in I will install and fire it up.
JamesW - I have cleaned the outside of the coil and replaced the ignitor I broke and started up the unit. It had an exhaust temperature of 317F. It ultimately climbed to 322F. Much lower than 409F when I started. I appears that I am getting 2.75 to 3.0 degree rise per hour. Maybe not back to the original specs but clearly much better. I will continue to monitor the exhaust temperature to see if there is more degradation. Thank you for the help. Rick
