Pentair mastertemp 400 cycling due to low gas flow?

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JamesW said:
Google how to make a manometer. Simple tubing on a board. Water height differential in inches is the pressure. Plus you'll need a 1/8" threaded to barbed fitting to go into the test hole.

You can buy a manometer if you want.

Natural gas can be run two stage with a 2 psi first stage from the meter to a regulator near the heater that steps down to the inlet pressure of the heater. This allows for smaller line for most of the run.

Note: Consult with a qualified gas contractor for anything you're not sure about. Don't do anything that you're not sure that you can do safely.
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I did a search, looks like a fun and simple project :) I will make the manometer this week and check the pressure, I don't see an obvious way to connect it inside the heater so will need to tap into the supply line right before the heater I guess... There is a union there won't be too hard to install a T.

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ps0303 said:
WOW, since day one and you lived with it?

Cycling on and off like that could also be something else other than gas flow.

When you get a chance, we need to know that when it cycles, does the service hater light come on. If it does, if you remove the top you can flip it over and look at the board to see which LED is on. You will need to remove the front and back panels and then up under the top in each corner is a wing nut. Remove all four and then the top will come off.
Click to expand...
I checked today. The service light does not come on. It's the heating light. It's solid when burner is firing, flashing when it cycles and burner is off (while blower still running), then comes on solid again when burner fires up again.

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setsailsoon said:
Bob,

I'm pretty new to pool equipment but I've done heat transfer and pipe sizing calculations for decades. For normal installations and gas systems you should have sufficient flow with 1-1/4" schedule 40 pipe. It could be close with all your other home gas consuming appliances on at once but not if they are all off. I'm assuming you've checked this out and it still cycles when you verify only pool heater is running? That being correct I like to trouble-shoot the safety stuff followed by the simple stuff first. So here's what I'd do, in order:


  1. You've probably already done this but to be sure and safe I've included this. Make sure there's no gas leak in the system. You indicated there's a gas smell when the unit runs. Is this only in the exhaust air while running? If not you have a gas leak. You can usually get your gas company to check this for free.
  2. Double check to be sure the line run to your heater is 11/4" and not reduced where it tee's off of the main line.
  3. Check to be sure the installer did not use flex pipe to make the final connection to your heater. That's a big no-no for most high btu demand devices like pool heaters.
  4. As RedBlue mentioned previously check the model number to be sure it's for natural gas not propane.
  5. Make sure your water pressure is not dropping too low due to a clogged water filter. Mine has a water pressure sensor on the inlet to sense water flow. If you're not sure about this by-pass the filter and see if the frequent heater cycling stops.
  6. When your heater shuts down it should have an indication of what caused the problem with an error coded or a blinking light. Find out what your code is. Could be the air flow through the burner. On mine (Jandy) I got an indication of "Check Ign Steps". Turned out it was a loose wire on one of the pressure sensors. A leaf over the fan inlet can cause the same error.
  7. If all the above check out, I'd call a qualified technician and request a tech that knows how to use a manometer to check pressure. This is waay cheaper than a $3000 line. Have him measure the pressure while the unit runs to check that the pressure is indeed too low when it shuts down and it's not a calibration issue with a sensor inside the heater. Please don't try this yourself unless you're really qualified to work with gas.

I hope this helps and please let us know what you find out.

Chris
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Thanks for the suggestions. The pipe size out of the the meter is 1 1/2 then it goes into a T one side goes into wall of hois and other side and reduces to 1 1/4 before it goes into ground on its way to pool heater. It comes out of the ground by heater as 1 1/4 then is reduced down to the size of the heater connection. There is a shutoff valve too right before the pipe into the heater.
The bad smell is the exhaust, not a leak, I was thinking perhaps it might not be burning completely if not enough pressure.
I checked the model number, it's 460736 which looks correct natural gas.
I am going to build a manometer this week and check pressure at the heater, when off and running. Then I will have my answer if the pressure is good :)

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Pentair Heater Gas Control Valve Kit 42001-0051S | Pentair 42001-0051S

Just above the pipe going into the valve is a small plug with an allen key receiver. It's visible in the pictures in the above link. One picture has the 1/8" pipe thread adaptor and the tubing for pressure testing.

The output of the valve (manifold side) also has a plug that says press tap. It's the same plug type. But don't test there, do it at the inlet side pressure tap point.

If you watch your water temperature readout on the automation display when the heater is firing, does the temperature move by a few degrees instantly?

Where is the water temperature probe that the automation uses for water temperature?

What rpm is the pump set for when heating?

Since it's not that old, have you considered putting in a warranty claim?

Note: Gas can be dangerous. It's best to have a qualified gas contractor evaluate the system. Don't do anything that you're not sure that you are qualified to do. Don't do anything that requires a license or certification.

Sometimes the best way to use information from the internet is to help understand what a service professional will be doing during their visit vs trying to do something you're not sure about.

Since you're not getting any error codes or a check heater light, I really don't think that the gas supply is the problem. I suspect that the service person really didn't know and just picked that because it's all they could think of. If they knew what they were doing, they would have pressure tested the line. Most likely the installer got something wrong while doing the installation, configuration or setup. They just blamed the one thing that they didn't do.

I would have a different, qualified service person check the system before you go messing with the gas supply.
 
bobca1 said:
Thanks for the suggestions. The pipe size out of the the meter is 1 1/2 then it goes into a T one side goes into wall of hois and other side and reduces to 1 1/4 before it goes into ground on its way to pool heater. It comes out of the ground by heater as 1 1/4 then is reduced down to the size of the heater connection. There is a shutoff valve too right before the pipe into the heater.
The bad smell is the exhaust, not a leak, I was thinking perhaps it might not be burning completely if not enough pressure.
I checked the model number, it's 460736 which looks correct natural gas.
I am going to build a manometer this week and check pressure at the heater, when off and running. Then I will have my answer if the pressure is good :)

Sent from mobile using Tapatalk
Click to expand...

Bob,

I read your recent posts in addition to this one. You've certainly run all the traps! I'm also re-thinking the manometer test. Although it would be interesting data it's not really likely to be the cause since you have no error code. I would think low inlet pressure would generate an error code and a system light error. This has me thinking it's more likely you have a sensor problem or at least a calibration issue. Could be the thermostat. If it "thinks" your temp is up to setting because it's out of calibration it would shut off the burner normally and not cause an error. You may want to find the thermostat connections wiggle them also just to be sure they're good. Food for thought anyway.

I hope this helps.

Chris
 
setsailsoon said:
Bob,

I read your recent posts in addition to this one. You've certainly run all the traps! I'm also re-thinking the manometer test. Although it would be interesting data it's not really likely to be the cause since you have no error code. I would think low inlet pressure would generate an error code and a system light error. This has me thinking it's more likely you have a sensor problem or at least a calibration issue. Could be the thermostat. If it "thinks" your temp is up to setting because it's out of calibration it would shut off the burner normally and not cause an error. You may want to find the thermostat connections wiggle them also just to be sure they're good. Food for thought anyway.

I hope this helps.

Chris
Click to expand...
I decided to skip the homemade manometer project, after seeing I could get a Pyle digital one an amazon for $58 that comes with the tube and 1/8 fitting. I want to also test and keep an eye on the propane pressure on my RV, so a compact meter will work well for that. Amazon should deliver it Wed I'll do the pressure test and give an update. I consider this pressure test critical step, then I will have certainty how to proceed (plumber or heater tech)

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JamesW said:
Pentair Heater Gas Control Valve Kit 42001-0051S | Pentair 42001-0051S

Just above the pipe going into the valve is a small plug with an allen key receiver. It's visible in the pictures in the above link. One picture has the 1/8" pipe thread adaptor and the tubing for pressure testing.

The output of the valve (manifold side) also has a plug that says press tap. It's the same plug type. But don't test there, do it at the inlet side pressure tap point.

If you watch your water temperature readout on the automation display when the heater is firing, does the temperature move by a few degrees instantly?

Where is the water temperature probe that the automation uses for water temperature?

What rpm is the pump set for when heating?

Since it's not that old, have you considered putting in a warranty claim?

Note: Gas can be dangerous. It's best to have a qualified gas contractor evaluate the system. Don't do anything that you're not sure that you are qualified to do. Don't do anything that requires a license or certification.

Sometimes the best way to use information from the internet is to help understand what a service professional will be doing during their visit vs trying to do something you're not sure about.

Since you're not getting any error codes or a check heater light, I really don't think that the gas supply is the problem. I suspect that the service person really didn't know and just picked that because it's all they could think of. If they knew what they were doing, they would have pressure tested the line. Most likely the installer got something wrong while doing the installation, configuration or setup. They just blamed the one thing that they didn't do.

I would have a different, qualified service person check the system before you go messing with the gas supply.
Click to expand...
The RPM is 2800 for heater/pool and 3200 when on spa.
Temp sensor on the automation is about 2 ft downstream of the pump outlet.

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bobca1 said:
I decided to skip the homemade manometer project, after seeing I could get a Pyle digital one an amazon for $58 that comes with the tube and 1/8 fitting. I want to also test and keep an eye on the propane pressure on my RV, so a compact meter will work well for that. Amazon should deliver it Wed I'll do the pressure test and give an update. I consider this pressure test critical step, then I will have certainty how to proceed (plumber or heater tech)

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Click to expand...

Well with this meter you can also measure the manifold side of the gas valve as it is a negative reading when the unit fires.

- - - Updated - - -

setsailsoon said:
Bob,

I read your recent posts in addition to this one. You've certainly run all the traps! I'm also re-thinking the manometer test. Although it would be interesting data it's not really likely to be the cause since you have no error code. I would think low inlet pressure would generate an error code and a system light error. This has me thinking it's more likely you have a sensor problem or at least a calibration issue. Could be the thermostat. If it "thinks" your temp is up to setting because it's out of calibration it would shut off the burner normally and not cause an error. You may want to find the thermostat connections wiggle them also just to be sure they're good. Food for thought anyway.

I hope this helps.

Chris
Click to expand...

There is not a error code for low gas pressure. It was a sensor issue then you should get an error code.
 
Meter came today one day early, thank you amazon prime :)
Right after connecting the meter had a pretty definitive diagnosis. Looks like it's time to write a big check for new line. I also did a test at the meter, no significant drop when heater came on (8.0 drop to 7.8 and that was with both heaters running in house at same time).

First photo is before burner fired, second photo shows while heating.
2f8507c9e74e819957b58eb2fe6f8434.jpg
582f7c734b9fa4628d6d97710fb516bc.jpg


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will said:
Again, I had same issue (even got the manometer) thought I was going to have to dig up 200' of line to enlarge. Instead, we used a regulator and created a high pressure line
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Thanks for letting me know, but with a drop in pressure so severe pretty sure now my line is shot. 30 years in the ground guess it must have rusted out. Probably will start leaking any day now.

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Before digging things up, i would exaust every possibiltiy that it might be something else. Gas meter, i know that it has larger pipe size in and out and looks big enough, but verify with the model number, it will tell you what the gas meter is rated at (BTUs it can supply), your heater needs 400K btu just by itself. Verify that the regulator is operating properly under load. A static test may not reveal a short coming. I stated i thought 90', you found that 100' is good, verify that your distance is under these lengths. Lastly, You can pressure test the gas line to make sure that it is still good, or if it leaks.
 
I know you said you have had the gas company install a larger meter but did you have them pressure test the line to the heater? I would hate to see you install a bigger line and still have a similar issue. Did you by chance do the readings as explained in the manual? As Pool Clown suggests as well, exhaust all possibilities before installing a larger pipe. Pipes usually rot from the outside in and will get a hole in them before any obstruction occurs.
 
ps0303 said:
Pipes usually rot from the outside in and will get a hole in them before any obstruction occurs.
Click to expand...
Unless of course *gulp* the line is half full of water. Perfect example of where you would get a normal static w/c reading and then a ridiculously low reading under load. But in your case, it has been like this since day one?

Tell me again why you have not called warranty???
 
JamesW said:
If the pipe is thirty years old, what did it go to before? Was the new heater a replacement for an old pool heater?
Click to expand...

Yes the mastertemp replaced the old pool heater which was probably the original heater. I'm not sure if the pipe is actually 30 years old, the tile in the pool looks to be from the 80's though, so my guess is the original owners build the pool in mod 80's.
 
There's a screen in the inlet to the gas valve to keep debris out of the valve. That would be worth checking. Also, taking apart some of the pipe near the heater would allow for inspection of the inside of the pipe. Check the sediment trap just outside of the heater to see what that's catching. Check the shut off valve just outside of the heater.

Check the regulator feeding the supply line to the heater.

Note: Make sure that anyone doing work on the gas supply is properly qualified to do so.

How many btu/hr was the old heater and did it work properly?
 

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