Mastertemp overheating issue

I would try a new stack flue temperature sensor first to verify the actual temperature.

If that doesn't make any difference, it might be a bad control board reading the temperature incorrectly.

Do you have a non-contact infrared temperature sensor that you can use to check the exhaust temperature?

If you feel the exhaust, is it super hot?

It should be hot but not super hot.

When the heat exchanger was removed, did you see calcium scale in the tubes?

If you were getting heavy scale in the heat exchanger, you would have heavy scale on the thermal regulator.
 
I figured I should chime in with an update on this issue. I decided not to replace any parts on my own since the service company was coming out to work on the issue. I'll jump to the end of the story - they replaced the heater under warranty from Pentair.

Now for the sad part - after 2 days of normal operation, the issue is back. It ran OK for about 12 hours after being replaced. I noticed early yesterday morning, after a 15 degree increase (a good rate - usually around 1 degree per hour), that the SFS temp reading was in the high 400s. Since the temp was about where I wanted it, and we were slated for 2 days of rain, I shut the heater down and lowered the pump speed to normal. Well, I fired it up this morning to raise it the 4 degrees I needed and it shut down after a few hours with the service heater light. I didn't have to guess or look further.

So, I'm in the same boat, after 2 months, a few hundred dollars, and only one decent day of pool use. Note that I paid a pool company to install, close, and open my pool to alleviate potential "new user error". New filter (also cleaned weekly now), new chem packs (Frog system), pool is clean, smells great, chemical balance good. Filter pressure 18 PSI on high, no obvious flow obstructions.

At this point, I'm just posting to close the story. I don't know what will happen from here or who can solve it. In IT we call this root cause analysis and I wish I could ask my PM team to handle it because I know they'd figure it out. Alas, they are not for hire.

Thanks for the help provided here.
Martin G.
 
You either have a water chemistry issue (see my post #12)
Or a low water flow issue
Or an exhaust issue

I think you have a water chemistry issue and you will not know without a good test kit doing your own testing.
 
Have you verified the gas pressure?

Can you describe the gas supply?

Is it natural or propane?

What is the pipe size and are there any regulators in the line?

Did they take the old heater apart to check for the cause of the problem?

What is the supply voltage and is the heater set to the right input voltage?
 
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JamesW: Answers inline:

Have you verified the gas pressure?

- 7lb static pressure with a drop of 1.5 when the heater is firing. Limits are 4-14 according to Pentair.

Can you describe the gas supply?

- Meter has 250k capacity. There is a 1x1x1 tee splitting off the run for the pool heater, furnace, and house water heater where the main line comes into the house. From the tee to the outside is ~ 20 feet, with another 90 feet to the heater itself. The pipe going to the heater is 1" in diameter. Our furnace is 75k BTU and the house water heater is about 40k I believe. Of these devices, only water heater may have been running at the same time as the pool heater, but not long periods of time.

Is it natural or propane?

- Natural

What is the pipe size and are there any regulators in the line?

- 1" and I am not aware of any regulators. It wasn't discussed and I'm not seeing anything additional in the work order.

Did they take the old heater apart to check for the cause of the problem?

- No, however most of the parts had been replaced at that point (exchanger, SFS, thermal regulator)

What is the supply voltage and is the heater set to the right input voltage?

- 110 is the input and I'm not sure what it's set to our how to check the heater setting. I'll look at the manual.

In regards to a gas contractor - the guy that's been coming out is their heater guy, but I don't know any service department for warranty will have one. I'm sure their installers have one. Aside from that, I can probably call the contractor back that installed my line for testing. There is a slight whine when the heater fires up occasionally. The tech that came out was able to adjust the gas valve to lesson/eliminate that (the valve the manual tells you not to touch without knowing what you're doing). The whine wasn't present when the heater was installed, it only started after about 5-6 firings later. It's very faint. If I can record a video and attach here I can do that.
 
You either have a water chemistry issue (see my post #12)
Or a low water flow issue
Or an exhaust issue

I think you have a water chemistry issue and you will not know without a good test kit doing your own testing.

I may be able to rule out flow and exhaust. Filter pressure is 18psi at the high pump speed, which is what everyone is telling me to run at with the heater going (vs. low where the pressure is at about 5psi). The jet at the return is fairly strong and I can feel the difference in temperature of the stream vs. the pool water. The exhaust for the heater is uninhibited - no walls, screens, etc. We have occasional wind gusting, but the days I ran the heater it was calm and I shut it down when a storm came through the day after.

I'll order a test kit (Taylor 2006 appears to be available on Amazon). The main reason I haven't is because I'm not sure I trust myself more than someone that has done the tests hundreds of times, and their computerized system which may make color matching more accurate vs. my eyes. I'll ask the pool store what they use next time I'm there.
 
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Is the pressure 7lb or 7"?

I'm thinking that the gas pressure is not correct.

Also, if the heater is not set for the correct voltage, that can cause problems.

Be very careful not to use the wrong voltage selector or the heater can be damaged. Measure voltage to be sure.

Based on the available information, I'm thinking that the flame is oversized and creating too much heat.

Maybe too much gas or the fan is not going fast enough to provide the correct amount of air.
 
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Is the pressure 7lb or 7"?

I'm thinking that the gas pressure is not correct.

Also, if the heater is not set for the correct voltage, that can cause problems.

Be very careful not to use the wrong voltage selector or the heater can be damaged. Measure voltage to be sure.

Based on the available information, I'm thinking that the flame is oversized and creating too much heat.

Maybe too much gas or the fan is not going fast enough to provide the correct amount of air.

Sorry - 7" water column.

I'll open another warranty case; the unit may need some adjustments. None were needed on the original unit (pool didn't have any water when it was originally installed last year - it simply worked, but I never checked the SFS temp as I didn't have a reason to). I did disconnected the return lines to flush them out and look for obstructions but I didn't find any. I also removed the chem packs from the Frog system and set the valve to "0" which basically sends the return water right through it without processing, also to eliminate potential obstructions/flow limiting factors.

Thanks
 
Were you able to verify that the correct voltage selector plug was used?

There are two voltage selector plugs in the metal box with the Fenwal Ignition Control Module.
 
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JamesW, I'll check that next time I'm outside.

I don't have the personal test kit yet, but I did talk to a Pentair rep that wanted me to get current good readings on chemical balance. I took another sample to the store. they use a system called "ClearCare" where the vials are inserted into a spectral scanner tool to read the color levels for the tests. Phosphate level was tested with a vial and a powder that turned the sample a medium blue color instantly.

Chlorine is all low, which I knew - the chem pack was empty and I've since replaced it. As for the others.. most are "OK" except for phosphates.

FC: 0, CC: 0, TC: 0 (correcting)
ph: 7.1
TA: 97
CH: 211
CYA: 10
Copper/Iron: 0
Phos: 1000 !!!!

So, I admit this was not being checked. I made an assumption about the 0 values on previous reports. I can correct this situation, but according to Pool School and some other guides, I can't tell if this can contribute to the heater issue or not. Someone did ask about phosphate levels earlier in this thread. I'll recheck all of this before firing the heater again (and wait until everything is in balance with chlorine, etc). Aside from the phosphate issue, using these values (even at 0 for all the chlorine measurements), the CSI ends up being low, as it has been. I'm guessing phosphate doesn't contribute since the PoolMath tool doesn't include it. Open to suggestions here.
 
In my opinion, the problem is probably the gas pressure. I would not run the heater until you can get a qualified gas contractor to check it out.

A licensed gas contractor, not a pool service technician.

The manifold pressure is actually -0.2" and it's tricky to measure correctly. See the manual for the procedure.

I asked about the phosphates. They would only be an issue if they were high enough to cause rapid scaling in the heat exchanger.

Phosphates are measured in ppb (parts per billion). So, 1,000 sounds scary but it's only 1 ppm.

In my opinion, scaling is probably not the issue. In my opinion the gas pressure is incorrect.
 
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I asked about the phosphates. They would only be an issue if they were high enough to cause rapid scaling in the heat exchanger.

Phosphates are measured in ppb (parts per billion). So, 1,000 sounds scary but it's only 1 ppm.

Since the whine is present, mostly (manual does mention this is a too-rich mixture) I'll go with that. I'll call the guys that ran my gas line and hooked up the heater initially. I also noticed I smell gas for about 2 seconds when it fires and shuts off (possible valve leak?)

What phosphate level is considered high enough to cause rapid scaling?

Thanks
 
1 ppm should not be an issue. I don't know what level would cause rapid scaling, but I think it has to be much higher than 1 ppm.

I would verify the correct voltage selector plug and the gas pressure.
 
I'll order a test kit (Taylor 2006 appears to be available on Amazon). The main reason I haven't is because I'm not sure I trust myself more than someone that has done the tests hundreds of times, and their computerized system which may make color matching more accurate vs. my eyes. I'll ask the pool store what they use next time I'm there.

Just browse around the forums here and you will read the many tales of people’s misplaced trust un pool stores. Their interests are not aligned with yours. They want to keep you coming back to buy more chemicals.

You are confusing precision with accuracy with their computerized system. Printouts of values to 2 decimal points does mot mean the results are accurate or repeatable. Some folks have posted the wide range of results when they have taken the same water to multiple pool stores for testing.

I hope you ordered the C model K-2006C and also the Speedstir Magnetic Stirrer
 
There's really only two or three options with a heater that is displaying an exhaust temp that high.
Sooted, (typically) calicified exchanger, or a bad temp sensor.
Essentially, the exchanger is just copper tubing with copper fins for more efficient thermal conductivity.
If the exterior of the exchanger is coated in soot, the soot will act as a thermal insulator, causing most of the heat from the flame holder to escape via exhaust. If the interior of the exchanger is coated in calcium, chemical residue, algae, whatever the case may be, same effect will occur.


Normal operating parameter on the heater is going to be 290-330 degrees F, anything higher is a sign of some sort of insulation on the exchanger preventing proper transfer of heat.

Unless it was a bad board, which I have honestly never seen fail in such a fashion that would cause the heater to read the exhaust as hotter than it actually is (normally, the exhaust will read as 80/40, and not really move from that). The SFS could be ohmed out, which should read 3.8-4.2 Mohms to be considered "good".


Seeing the report from the chemical analysis, that does indicate there would be likely some interesting things going on internally due to chemistry of the system. Phosphates, by and large, are bad for your pool. Being a food source for algae, removal is advisable, but obviously if you have a algae situation you're wanting to add algaecide and shock and regular chlorine additions in order to mitigate that problem, but part of the equation ends up being removal of the food source.



Typical gas tends to be 8-10" WC static, no more than a 2 " WC drop when firing for natural gas. But the spec is 4-14" WC technically. So, your burn will not be ideal, but it shouldn't be problematic in the normal life expectancy of the heater. I have never seen a heater exhibit a problem as you've describe, with too large/powerful of a flame. If the gas line readings are accurate, that isn't the issue at all.


Trying to understand the situation as it is presented, but the principle of the heater and the behavior being exhibited aren't meshing well at all. I'd be very interested in knowing who the service team from Pentair is, and what their determination is because it isn't clicking as to what the cause of the problem is here.
 
Now for the sad part - after 2 days of normal operation, the issue is back. It ran OK for about 12 hours after being replaced. I noticed early yesterday morning, after a 15 degree increase (a good rate - usually around 1 degree per hour), that the SFS temp reading was in the high 400s.

So, you say that it ran ok for a while, but did you check the stack flue temperature when it first started?

Based on the short time period, I don't see how the heat exchanger is going to get scaled up in a few hours of runtime unless you have some really strange chemistry going on. The pictures that were posted earlier show no scale.

If the exchanger sooted up that fast, it would point to a gas pressure issue.

In my opinion, it's almost definitely a gas pressure issue.

Hopefully, a qualified gas contractor will be able to figure it out.
 
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